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• How can I write faster JavaScript?

  - by a paid nerd

  I'm writing an HTML5 canvas visualization. According to the Chrome Developer Tools profiler, 90% of the work is being done in (program), which I assume is the V8 interpreter at work calling functions and switching contexts and whatnot. Other than logic optimizations (e.g., only redrawing parts of the visualization that have changed), what can I do to optimize the CPU usage of my JavaScript? I'm willing to sacrifice some amount of readability and extensibility for performance. Is there a big list I'm missing because my Google skills suck? I have some ideas but I'm not sure if they're worth it: Limit function calls When possible, use arrays instead of objects and properties Use variables for math operation results as much as possible Cache common math operations such as Math.PI / 180 Use sin and cos approximation functions instead of Math.sin() and Math.cos() Reuse objects when passing around data instead of creating new ones Replace Math.abs() with ~~ Study jsperf.com until my eyes bleed Use a preprocessor on my JavaScript to do some of the above operations

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• Include upper bound in range()

  - by Jull

  How can I include the upper bound in range() function? I can't add by 1 because my for-loop looks like: for x in range(1,math.floor(math.sqrt(x))): y = math.sqrt(n - x * x) But as I understand it will actually be 1 < x < M where I need 1 < x <= M Adding 1 will completely change the result. I am trying to rewrite my old program from C# to Python. That's how it looked in C#: for (int x = 1; x <= Math.Floor(Math.Sqrt(n)); x++) double y = Math.Sqrt(n - x * x);

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• Updating the value of a math equation with YUI slider and simple radio buttons.

  - by dj lewis

  I have a form that is used to show a price for a product. I have a YUI slider setup that changes the price, and it works perfectly. Now I'm trying to add in radio buttons that also should update that same price value. The price displayed should take into account all 3 fields, and update dynamically as any are updated. This is the code I have, but I don't have any radio buttons for cpanelPrice yet as I'm still just trying to get the IPs to work. <script type="text/javascript"> (function() { var Event = YAHOO.util.Event, Dom = YAHOO.util.Dom, lang = YAHOO.lang, slider, bg="slider-bg", thumb="slider-thumb", orderlink="order-link", monthlyprice="monthly-price", dram="ram", stor="storage",dcpu="cpu",bandw="bandwidth",slid="sliderbg" // The slider can move 0 pixels up var topConstraint = 0; // The slider can move 200 pixels down var bottomConstraint = 585; // Custom scale factor for converting the pixel offset into a real value var scaleFactor = 1; // The amount the slider moves when the value is changed with the arrow // keys var keyIncrement = 65; var tickSize = 65; Event.onDOMReady(function() { slider = YAHOO.widget.Slider.getHorizSlider(bg, thumb, topConstraint, bottomConstraint, tickSize); slider.setValue(1, true); slider.animate = true; slider.getRealValue = function() { return Math.round(this.getValue() * scaleFactor); } slider.subscribe("change", function(offsetFromStart) { var ordnode = Dom.get(orderlink); var prinode = Dom.get(monthlyprice); var ramnode = Dom.get(dram); var stornode = Dom.get(stor); var cpunode = Dom.get(dcpu); var bwnode = Dom.get(bandw); var slidnode = Dom.get(slid); var actualValue = slider.getRealValue(); if (actualValue < 0) { var actualValue = 0; } if (actualValue > -1 && actualValue < 5) { basePrice = 15; var pid = "7"; var ram = "128 MB"; stornode.innerHTML = "5"; cpunode.innerHTML = ".5"; bwnode.innerHTML = "50"; slidnode.innerHTML = "<img src=\"/images/sliderbg1.png\" alt=\"\" />"; } else if (actualValue > 60 && actualValue < 70) { basePrice = 25; var pid = "8"; var ram = "256 MB"; stornode.innerHTML = "10"; cpunode.innerHTML = ".5"; bwnode.innerHTML = "100"; slidnode.innerHTML = "<img src=\"/images/sliderbg2.png\" alt=\"\" />"; } else if (actualValue > 125 && actualValue < 135) { basePrice = 40; var pid = "9"; var ram = "512 MB"; stornode.innerHTML = "20"; cpunode.innerHTML = "1"; bwnode.innerHTML = "200"; slidnode.innerHTML = "<img src=\"/images/sliderbg3.png\" alt=\"\" />"; } else if (actualValue > 190 && actualValue < 200) { basePrice = 60; var pid = "10"; var ram = "1 GB"; stornode.innerHTML = "40"; cpunode.innerHTML = "1"; bwnode.innerHTML = "400"; slidnode.innerHTML = "<img src=\"/images/sliderbg4.png\" alt=\"\" />"; } else if (actualValue> 255 && actualValue < 265) { basePrice = 80; var pid = "11"; var ram = "1.5 GB"; stornode.innerHTML = "60"; cpunode.innerHTML = "1"; bwnode.innerHTML = "600"; slidnode.innerHTML = "<img src=\"/images/sliderbg5.png\" alt=\"\" />"; } else if (actualValue > 320 && actualValue < 330) { basePrice = 110; var pid = "12"; var ram = "2 GB"; stornode.innerHTML = "80"; cpunode.innerHTML = "2"; bwnode.innerHTML = "800"; slidnode.innerHTML = "<img src=\"/images/sliderbg6.png\" alt=\"\" />"; } else if (actualValue > 385 && actualValue < 395) { basePrice = 140; var pid = "13"; var ram = "2.5 GB"; stornode.innerHTML = "100"; cpunode.innerHTML = "2"; bwnode.innerHTML = "1000"; slidnode.innerHTML = "<img src=\"/images/sliderbg7.png\" alt=\"\" />"; } else if (actualValue > 450 && actualValue < 460) { basePrice = 170; var pid = "14"; var ram = "3 GB"; stornode.innerHTML = "120"; cpunode.innerHTML = "3"; bwnode.innerHTML = "1200"; slidnode.innerHTML = "<img src=\"/images/sliderbg8.png\" alt=\"\" />"; } else if (actualValue > 515 && actualValue < 525) { basePrice = 200; var pid = "15"; var ram = "3.5 GB"; stornode.innerHTML = "140"; cpunode.innerHTML = "3"; bwnode.innerHTML = "1400"; slidnode.innerHTML = "<img src=\"/images/sliderbg9.png\" alt=\"\" />"; } else if (actualValue > 580 && actualValue < 590) { basePrice = 240; var pid = "16"; var ram = "4 GB"; stornode.innerHTML = "160"; cpunode.innerHTML = "4"; bwnode.innerHTML = "1600"; slidnode.innerHTML = "<img src=\"/images/sliderbg10.png\" alt=\"\" />"; } // Setup the order link ordnode.innerHTML = "<a href=\"https://account.hostingbeast.com/cart.php?a=add&pid=" + pid + "\"><img src=\"/images/blank.gif\" alt=\"Order VPS Hosting\" height=\"100\" width=\"100\" /></a>"; ramnode.innerHTML = ram; ipPrice = 0; function setIpPrice(ips) { ipPrice = ips.value; } cpanelPrice = 0; prinode.innerHTML = basePrice + ipPrice + cpanelPrice; }); // Use setValue to reset the value to white: Event.on("putval", "click", function(e) { slider.setValue(100, false); //false here means to animate if possible }); setTimeout(function () { slider.setValue(10); },0); }); })(); </script> <div style="width: 649px; margin:auto"> <span id="sliderbg"></span> <div class="yui-skin-sam"> <div id="slider-bg" class="yui-h-slider" tabindex="-1"> <div id="slider-thumb" class="yui-slider-thumb"><img src="/images/thumb-bar.png"></div> </div> </div> </div> <div class="vpsdetails"> <div id="vpsprod"><span id="cpu"></span></div> <div id="vpsram"><span id="ram"></span></div> <div id="vpsstor"><span id="storage"></span> GB</div> <div id="vpsbw"><span id="bandwidth"></span> GB</div> <div id="slideprice">$ <span id="monthly-price"></span></div> </div> <input type="radio" name="ips" value="2" onclick="setIpPrice(this.value - 2 * 2);" checked="checked" /> 2 <input type="radio" name="ips" value="4" onclick="setIpPrice(this.value - 2 * 2);" /> 4

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• Probability Selector

  For when you really do need randomness Probability - Math - Event - Teaching Resources - Past Events

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• Tile engine Texture not updating when numbers in array change

  - by Corey

  I draw my map from a txt file. I am using java with slick2d library. When I print the array the number changes in the array, but the texture doesn't change. public class Tiles { public Image[] tiles = new Image[5]; public int[][] map = new int[64][64]; public Image grass, dirt, fence, mound; private SpriteSheet tileSheet; public int tileWidth = 32; public int tileHeight = 32; public void init() throws IOException, SlickException { tileSheet = new SpriteSheet("assets/tiles.png", tileWidth, tileHeight); grass = tileSheet.getSprite(0, 0); dirt = tileSheet.getSprite(7, 7); fence = tileSheet.getSprite(2, 0); mound = tileSheet.getSprite(2, 6); tiles[0] = grass; tiles[1] = dirt; tiles[2] = fence; tiles[3] = mound; int x=0, y=0; BufferedReader in = new BufferedReader(new FileReader("assets/map.dat")); String line; while ((line = in.readLine()) != null) { String[] values = line.split(","); x = 0; for (String str : values) { int str_int = Integer.parseInt(str); map[x][y]=str_int; //System.out.print(map[x][y] + " "); x++; } //System.out.println(""); y++; } in.close(); } public void update(GameContainer gc) { } public void render(GameContainer gc) { for(int y = 0; y < map.length; y++) { for(int x = 0; x < map[0].length; x ++) { int textureIndex = map[x][y]; Image texture = tiles[textureIndex]; texture.draw(x*tileWidth,y*tileHeight); } } } } Mouse Picking Where I change the number in the array Input input = gc.getInput(); gc.getInput().setOffset(cameraX-400, cameraY-300); float mouseX = input.getMouseX(); float mouseY = input.getMouseY(); double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { System.out.println("Clicked"); if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } I never ask a question until I have tried to figure it out myself. I have been stuck with this problem for two weeks. It's not like this site is made for asking questions or anything. So if you actually try to help me instead of telling me to use a debugger thank you. You either get told you have too much or too little code. Nothing is never enough for the people on here it's as bad as something like reddit. Idk what is wrong all my textures work when I render them it just doesn't update when the number in the array changes. I am obviously debugging when I say that I was printing the array and the number is changing like it should, so it's not a problem with my mouse picking code. It is a problem with my textures, but I don't know what because they all render correctly. That is why I need help.

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• Adding objects to the environment at timed intervals

  - by david

  I am using an ArrayList to handle objects and at each interval of 120 frames, I am adding a new object of the same type at a random location along the z-axis of 60. The problem is, it doesn't add just 1. It depends on how many are in the list. If I kill the Fox before the time interval when one is supposed to spawn comes, then no Fox will be spawned. If I don't kill any foxes, it grows exponentially. I only want one Fox to be added every 120 frames. This problem never happened before when I created new ones and added them to the environment. Any insights? Here is my code: /**** FOX CLASS ****/ import env3d.EnvObject; import java.util.ArrayList; public class Fox extends Creature { private int frame = 0; public Fox(double x, double y, double z) { super(x, y, z); // Must use the mutator as the fields have private access // in the parent class setTexture("models/fox/fox.png"); setModel("models/fox/fox.obj"); setScale(1.4); } public void move(ArrayList<Creature> creatures, ArrayList<Creature> dead_creatures, ArrayList<Creature> new_creatures) { frame++; setX(getX()-0.2); setRotateY(270); if (frame > 120) { Fox f = new Fox(60, 1, (int)(Math.random()*28)+1); new_creatures.add(f); frame = 0; } for (Creature c : creatures) { if (this.distance(c) < this.getScale()+c.getScale() && c instanceof Tux) { dead_creatures.add(c); } } for (Creature c : creatures) { if (c.getX() < 1 && c instanceof Fox) { dead_creatures.add(c); } } } } import env3d.Env; import java.util.ArrayList; import org.lwjgl.input.Keyboard; /** * A predator and prey simulation. Fox is the predator and Tux is the prey. */ public class Game { private Env env; private boolean finished; private ArrayList<Creature> creatures; private KingTux king; private Snowball ball; private int tuxcounter; private int kills; /** * Constructor for the Game class. It sets up the foxes and tuxes. */ public Game() { // we use a separate ArrayList to keep track of each animal. // our room is 50 x 50. creatures = new ArrayList<Creature>(); for (int i = 0; i < 10; i++) { creatures.add(new Tux((int)(Math.random()*10)+1, 1, (int)(Math.random()*28)+1)); } for (int i = 0; i < 1; i++) { creatures.add(new Fox(60, 1, (int)(Math.random()*28)+1)); } king = new KingTux(25, 1, 35); ball = new Snowball(-400, -400, -400); } /** * Play the game */ public void play() { finished = false; // Create the new environment. Must be done in the same // method as the game loop env = new Env(); // Make the room 50 x 50. env.setRoom(new Room()); // Add all the animals into to the environment for display for (Creature c : creatures) { env.addObject(c); } for (Creature c : creatures) { if (c instanceof Tux) { tuxcounter++; } } env.addObject(king); env.addObject(ball); // Sets up the camera env.setCameraXYZ(30, 50, 55); env.setCameraPitch(-63); // Turn off the default controls env.setDefaultControl(false); // A list to keep track of dead tuxes. ArrayList<Creature> dead_creatures = new ArrayList<Creature>(); ArrayList<Creature> new_creatures = new ArrayList<Creature>(); // The main game loop while (!finished) { if (env.getKey() == 1 || tuxcounter == 0) { finished = true; } env.setDisplayStr("Tuxes: " + tuxcounter, 15, 0); env.setDisplayStr("Kills: " + kills, 140, 0); processInput(); ball.move(); king.check(); // Move each fox and tux. for (Creature c : creatures) { c.move(creatures, dead_creatures, new_creatures); } for (Creature c : creatures) { if (c.distance(ball) < c.getScale()+ball.getScale() && c instanceof Fox) { dead_creatures.add(c); ball.setX(-400); ball.setY(-400); ball.setZ(-400); kills++; } } // Clean up of the dead tuxes. for (Creature c : dead_creatures) { if (c instanceof Tux) { tuxcounter--; } env.removeObject(c); creatures.remove(c); } for (Creature c : new_creatures) { creatures.add(c); env.addObject(c); } // we clear the ArrayList for the next loop. We could create a new one // every loop but that would be very inefficient. dead_creatures.clear(); new_creatures.clear(); // Update display env.advanceOneFrame(); } // Just a little clean up env.exit(); } private void processInput() { int keyDown = env.getKeyDown(); int key = env.getKey(); if (keyDown == 203) { king.setX(king.getX()-1); } else if (keyDown == 205) { king.setX(king.getX()+1); } if (ball.getX() <= -400 && key == Keyboard.KEY_S) { ball.setX(king.getX()); ball.setY(king.getY()); ball.setZ(king.getZ()); } } /** * Main method to launch the program. */ public static void main(String args[]) { (new Game()).play(); } } /**** CREATURE CLASS ****/ /* (Parent class to Tux, Fox, and KingTux) */ import env3d.EnvObject; import java.util.ArrayList; abstract public class Creature extends EnvObject { private int frame; private double rand; /** * Constructor for objects of class Creature */ public Creature(double x, double y, double z) { setX(x); setY(y); setZ(z); setScale(1); rand = Math.random(); } private void randomGenerator() { rand = Math.random(); } public void move(ArrayList<Creature> creatures, ArrayList<Creature> dead_creatures, ArrayList<Creature> new_creatures) { frame++; if (frame > 12) { randomGenerator(); frame = 0; } // if (rand < 0.25) { // setX(getX()+0.3); // setRotateY(90); // } else if (rand < 0.5) { // setX(getX()-0.3); // setRotateY(270); // } else if (rand < 0.75) { // setZ(getZ()+0.3); // setRotateY(0); // } else if (rand < 1) { // setZ(getZ()-0.3); // setRotateY(180); // } if (rand < 0.5) { setRotateY(getRotateY()-7); } else if (rand < 1) { setRotateY(getRotateY()+7); } setX(getX()+Math.sin(Math.toRadians(getRotateY()))*0.5); setZ(getZ()+Math.cos(Math.toRadians(getRotateY()))*0.5); if (getX() < getScale()) setX(getScale()); if (getX() > 50-getScale()) setX(50 - getScale()); if (getZ() < getScale()) setZ(getScale()); if (getZ() > 50-getScale()) setZ(50 - getScale()); // The move method now handles collision detection if (this instanceof Fox) { for (Creature c : creatures) { if (c.distance(this) < c.getScale()+this.getScale() && c instanceof Tux) { dead_creatures.add(c); } } } } } The rest of the classes are a bit trivial to this specific problem.

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• Ubuntu 12.04 + Raid0 + Windows 7 not loading

  - by Douglas

  please someone help me.... (Sorry for my english) Hi, I have a Pc with 2 Hd (1Tb each) on Raid0. I had a Windows 7 64bits working for several months. When I installed the Windows I let a 100Gb partition empty to install Ubuntu someday. I was using Linux on a Virtualbox, but this week I tried to install Ubuntu 12.04 in this 100Gb partition. I used the Ubuntu alternate cd, because the 'normal' cd was giving me trouble with the Raid0. The grub installation always reported a error. After a lot of work I found that I nedded to install grub on partition /dev/mapper/isw_chjbfeec_DougRaid1 (see Bootinfo below). The Windows installation created a 100Mb boot partition, so I needed to install grub in this partition. Now I have the Ubuntu working 100% ok. The problem is, the Windows is not booting! The windows option is present on the grub menu, but when I choose the windows option there is a black screen and after that the grub is reloaded. My Bootinfo is: Boot Info Script 0.61 [1 April 2012] ============================= Boot Info Summary: =============================== => Grub2 (v1.99) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for /boot/grub. => Grub2 (v1.99) is installed in the MBR of /dev/mapper/isw_chjbfeec_DougRaid and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for /boot/grub. sda1: __________________________________________________________________________ File system: Boot sector type: Unknown Boot sector info: Mounting failed: mount: unknown filesystem type '' sda2: __________________________________________________________________________ File system: Boot sector type: Unknown Boot sector info: Mounting failed: mount: unknown filesystem type '' mount: unknown filesystem type '' sda3: __________________________________________________________________________ File system: Extended Partition Boot sector type: Unknown Boot sector info: isw_chjbfeec_DougRaid1: ________________________________________________________ File system: ntfs Boot sector type: Grub2 (v1.99) Boot sector info: Grub2 (v1.99) is installed in the boot sector of isw_chjbfeec_DougRaid1 and looks at sector 3841862992 of the same hard drive for core.img. core.img is at this location and looks for (,msdos5)/boot/grub on this drive. No errors found in the Boot Parameter Block. Operating System: Boot files: /grldr /bootmgr /Boot/BCD /grldr isw_chjbfeec_DougRaid2: ________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Windows 7 Boot files: /Windows/System32/winload.exe isw_chjbfeec_DougRaid3: ________________________________________________________ File system: Extended Partition Boot sector type: - Boot sector info: isw_chjbfeec_DougRaid5: ________________________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Ubuntu 12.04 LTS Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/core.img isw_chjbfeec_DougRaid6: ________________________________________________________ File system: swap Boot sector type: - Boot sector info: ============================ Drive/Partition Info: ============================= Drive: sda _____________________________________________________________________ Partition Boot Start Sector End Sector # of Sectors Id System /dev/sda1 * 2,048 206,847 204,800 7 NTFS / exFAT / HPFS /dev/sda2 206,848 3,686,402,047 3,686,195,200 7 NTFS / exFAT / HPFS /dev/sda3 3,686,402,558 3,907,039,743 220,637,186 5 Extended Invalid MBR Signature found. EBR refers to a location outside the hard drive. /dev/sda2 ends after the last sector of /dev/sda /dev/sda3 ends after the last sector of /dev/sda Drive: isw_chjbfeec_DougRaid _____________________________________________________________________ Disk /dev/mapper/isw_chjbfeec_DougRaid: 2000.4 GB, 2000404348928 bytes 255 heads, 63 sectors/track, 243201 cylinders, total 3907039744 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/mapper/isw_chjbfeec_DougRaid1 * 2,048 206,847 204,800 7 NTFS / exFAT / HPFS /dev/mapper/isw_chjbfeec_DougRaid2 206,848 3,686,402,047 3,686,195,200 7 NTFS / exFAT / HPFS /dev/mapper/isw_chjbfeec_DougRaid3 3,686,402,558 3,907,039,743 220,637,186 5 Extended /dev/mapper/isw_chjbfeec_DougRaid5 3,686,402,560 3,881,876,479 195,473,920 83 Linux /dev/mapper/isw_chjbfeec_DougRaid6 3,881,876,992 3,907,039,743 25,162,752 82 Linux swap / Solaris "blkid" output: ________________________________________________________________ Device UUID TYPE LABEL /dev/mapper/isw_chjbfeec_DougRaid1 C89C73D19C73B910 ntfs Reservado pelo Sistema /dev/mapper/isw_chjbfeec_DougRaid2 6830883A3088116C ntfs /dev/mapper/isw_chjbfeec_DougRaid5 bbab868a-ea53-4be3-ba7d-2737fe6cb24c ext4 /dev/mapper/isw_chjbfeec_DougRaid6 7a830a3c-88fb-4cba-80dc-f32e08abfd5b swap /dev/sda isw_raid_member /dev/sdb isw_raid_member /dev/sr0 iso9660 Windows7x86x64SK ========================= "ls -R /dev/mapper/" output: ========================= /dev/mapper: control isw_chjbfeec_DougRaid isw_chjbfeec_DougRaid1 isw_chjbfeec_DougRaid2 isw_chjbfeec_DougRaid3 isw_chjbfeec_DougRaid5 isw_chjbfeec_DougRaid6 ================================ Mount points: ================================= Device Mount_Point Type Options /dev/mapper/isw_chjbfeec_DougRaid5 / ext4 (rw,errors=remount-ro) /dev/sr0 /media/Windows7x86x64SK iso9660 (ro,nosuid,nodev,uid=1000,gid=1000,iocharset=utf8,mode=0400,dmode=0500,uhelper=udisks) ================= isw_chjbfeec_DougRaid1/grldr embedded menu: ================== -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ================== isw_chjbfeec_DougRaid5/boot/grub/grub.cfg: ================== -------------------------------------------------------------------------------- # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { insmod vbe insmod vga insmod video_bochs insmod video_cirrus } insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=auto load_video insmod gfxterm insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c set locale_dir=($root)/boot/grub/locale set lang=en_US insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ]; then set timeout=-1 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="$1" if [ "$1" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ ${recordfail} != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode if [ "$linux_gfx_mode" != "text" ]; then load_video; fi menuentry 'Ubuntu, with Linux 3.2.0-24-generic-pae' --class ubuntu --class gnu-linux --class gnu --class os { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c linux /boot/vmlinuz-3.2.0-24-generic-pae root=UUID=bbab868a-ea53-4be3-ba7d-2737fe6cb24c ro quiet splash $vt_handoff initrd /boot/initrd.img-3.2.0-24-generic-pae } menuentry 'Ubuntu, with Linux 3.2.0-24-generic-pae (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod gzio insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c echo 'Loading Linux 3.2.0-24-generic-pae ...' linux /boot/vmlinuz-3.2.0-24-generic-pae root=UUID=bbab868a-ea53-4be3-ba7d-2737fe6cb24c ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.2.0-24-generic-pae } submenu "Previous Linux versions" { menuentry 'Ubuntu, with Linux 3.2.0-23-generic-pae' --class ubuntu --class gnu-linux --class gnu --class os { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c linux /boot/vmlinuz-3.2.0-23-generic-pae root=UUID=bbab868a-ea53-4be3-ba7d-2737fe6cb24c ro quiet splash $vt_handoff initrd /boot/initrd.img-3.2.0-23-generic-pae } menuentry 'Ubuntu, with Linux 3.2.0-23-generic-pae (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod gzio insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c echo 'Loading Linux 3.2.0-23-generic-pae ...' linux /boot/vmlinuz-3.2.0-23-generic-pae root=UUID=bbab868a-ea53-4be3-ba7d-2737fe6cb24c ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.2.0-23-generic-pae } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='(/dev/mapper/isw_chjbfeec_DougRaid3,msdos1)' search --no-floppy --fs-uuid --set=root bbab868a-ea53-4be3-ba7d-2737fe6cb24c linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober_proxy ### menuentry "Windows 7 (loader) (on /dev/mapper/isw_chjbfeec_DougRaid1)" --class windows --class os { insmod part_msdos insmod ntfs set root='(sda,msdos1)' search --no-floppy --fs-uuid --set=root C89C73D19C73B910 chainloader +1 } ### END /etc/grub.d/30_os-prober_proxy ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### -------------------------------------------------------------------------------- ====================== isw_chjbfeec_DougRaid5/etc/fstab: ======================= -------------------------------------------------------------------------------- # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 /dev/mapper/isw_chjbfeec_DougRaid5 / ext4 errors=remount-ro 0 1 /dev/mapper/isw_chjbfeec_DougRaid6 none swap sw 0 0 -------------------------------------------------------------------------------- ========== isw_chjbfeec_DougRaid5: Location of files loaded by Grub: =========== GiB - GB File Fragment(s) = boot/grub/core.img 1 = boot/grub/grub.cfg 1 = boot/initrd.img-3.2.0-23-generic-pae 2 = boot/initrd.img-3.2.0-24-generic-pae 2 = boot/vmlinuz-3.2.0-23-generic-pae 1 = boot/vmlinuz-3.2.0-24-generic-pae 1 = initrd.img 2 = initrd.img.old 2 = vmlinuz 1 = vmlinuz.old 1 ======================== Unknown MBRs/Boot Sectors/etc: ======================== Unknown BootLoader on sda1 Unknown BootLoader on sda2 Unknown BootLoader on sda3 =============================== StdErr Messages: =============================== xz: (stdin): Compressed data is corrupt xz: (stdin): Compressed data is corrupt hexdump: /dev/sda1: No such file or directory hexdump: /dev/sda1: No such file or directory hexdump: /dev/sda2: No such file or directory hexdump: /dev/sda2: No such file or directory hexdump: /dev/sda3: No such file or directory hexdump: /dev/sda3: No such file or directory xz: (stdin): Compressed data is corrupt awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in How we can see the Windows part at grub is: menuentry "Windows 7 (loader) (on /dev/mapper/isw_chjbfeec_DougRaid1)" --class windows --class os { insmod part_msdos insmod ntfs set root='(sda,msdos1)' search --no-floppy --fs-uuid --set=root C89C73D19C73B910 chainloader +1 } I tried a lot of combinations at the line: set root='(sda,msdos1)' , but no success I tried to change uuid to the /dev/mapper/isw_chjbfeec_DougRaid2 uuid, but the grub reports a error. I dont know what to do now. I really need to boot my windows partition. Someone knows what to do? Thanks........

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• Tile-based 2D collision detection problems

  - by Vee

  I'm trying to follow this tutorial http://www.tonypa.pri.ee/tbw/tut05.html to implement real-time collisions in a tile-based world. I find the center coordinates of my entities thanks to these properties: public float CenterX { get { return X + Width / 2f; } set { X = value - Width / 2f; } } public float CenterY { get { return Y + Height / 2f; } set { Y = value - Height / 2f; } } Then in my update method, in the player class, which is called every frame, I have this code: public override void Update() { base.Update(); int downY = (int)Math.Floor((CenterY + Height / 2f - 1) / 16f); int upY = (int)Math.Floor((CenterY - Height / 2f) / 16f); int leftX = (int)Math.Floor((CenterX + Speed * NextX - Width / 2f) / 16f); int rightX = (int)Math.Floor((CenterX + Speed * NextX + Width / 2f - 1) / 16f); bool upleft = Game.CurrentMap[leftX, upY] != 1; bool downleft = Game.CurrentMap[leftX, downY] != 1; bool upright = Game.CurrentMap[rightX, upY] != 1; bool downright = Game.CurrentMap[rightX, downY] != 1; if(NextX == 1) { if (upright && downright) CenterX += Speed; else CenterX = (Game.GetCellX(CenterX) + 1)*16 - Width / 2f; } } downY, upY, leftX and rightX should respectively find the lowest Y position, the highest Y position, the leftmost X position and the rightmost X position. I add + Speed * NextX because in the tutorial the getMyCorners function is called with these parameters: getMyCorners (ob.x+ob.speed*dirx, ob.y, ob); The GetCellX and GetCellY methods: public int GetCellX(float mX) { return (int)Math.Floor(mX / SGame.Camera.TileSize); } public int GetCellY(float mY) { return (int)Math.Floor(mY / SGame.Camera.TileSize); } The problem is that the player "flickers" while hitting a wall, and the corner detection doesn't even work correctly since it can overlap walls that only hit one of the corners. I do not understand what is wrong. In the tutorial the ob.x and ob.y fields should be the same as my CenterX and CenterY properties, and the ob.width and ob.height should be the same as Width / 2f and Height / 2f. However it still doesn't work. Thanks for your help.

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• Arbitrary Rotation about a Sphere

  - by Der

  I'm coding a mechanic which allows a user to move around the surface of a sphere. The position on the sphere is currently stored as theta and phi, where theta is the angle between the z-axis and the xz projection of the current position (i.e. rotation about the y axis), and phi is the angle from the y-axis to the position. I explained that poorly, but it is essentially theta = yaw, phi = pitch Vector3 position = new Vector3(0,0,1); position.X = (float)Math.Sin(phi) * (float)Math.Sin(theta); position.Y = (float)Math.Sin(phi) * (float)Math.Cos(theta); position.Z = (float)Math.Cos(phi); position *= r; I believe this is accurate, however I could be wrong. I need to be able to move in an arbitrary pseudo two dimensional direction around the surface of a sphere at the origin of world space with radius r. For example, holding W should move around the sphere in an upwards direction relative to the orientation of the player. I believe I should be using a Quaternion to represent the position/orientation on the sphere, but I can't think of the correct way of doing it. Spherical geometry is not my strong suit. Essentially, I need to fill the following block: public void Move(Direction dir) { switch (dir) { case Direction.Left: // update quaternion to rotate left break; case Direction.Right: // update quaternion to rotate right break; case Direction.Up: // update quaternion to rotate upward break; case Direction.Down: // update quaternion to rotate downward break; } }

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• Ball bouncing at a certain angle and efficiency computations

  - by X Y

  I would like to make a pong game with a small twist (for now). Every time the ball bounces off one of the paddles i want it to be under a certain angle (between a min and a max). I simply can't wrap my head around how to actually do it (i have some thoughts and such but i simply cannot implement them properly - i feel i'm overcomplicating things). Here's an image with a small explanation . One other problem would be that the conditions for bouncing have to be different for every edge. For example, in the picture, on the two small horizontal edges i do not want a perfectly vertical bounce when in the middle of the edge but rather a constant angle (pi/4 maybe) in either direction depending on the collision point (before the middle of the edge, or after). All of my collisions are done with the Separating Axes Theorem (and seem to work fine). I'm looking for something efficient because i want to add a lot of things later on (maybe polygons with many edges and such). So i need to keep to a minimum the amount of checking done every frame. The collision algorithm begins testing whenever the bounding boxes of the paddle and the ball intersect. Is there something better to test for possible collisions every frame? (more efficient in the long run,with many more objects etc, not necessarily easy to code). I'm going to post the code for my game: Paddle Class public class Paddle : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private bool keybEnabled; private bool isLeftPaddle; private Texture2D paddleSprite; private Vector2 paddlePosition; private float paddleSpeedY; private Vector2 paddleScale = new Vector2(1f, 1f); private const float DEFAULT_Y_SPEED = 150; private Vector2[] Normals2Edges; private Vector2[] Vertices = new Vector2[4]; private List<Vector2> lst = new List<Vector2>(); private Vector2 Edge; #endregion #region Properties public float Speed { get {return paddleSpeedY; } set { paddleSpeedY = value; } } public Vector2[] Normal2EdgesVector { get { NormalsToEdges(this.isLeftPaddle); return Normals2Edges; } } public Vector2[] VertexVector { get { return Vertices; } } public Vector2 Scale { get { return paddleScale; } set { paddleScale = value; NormalsToEdges(this.isLeftPaddle); } } public float X { get { return paddlePosition.X; } set { paddlePosition.X = value; } } public float Y { get { return paddlePosition.Y; } set { paddlePosition.Y = value; } } public float Width { get { return (Scale.X == 1f ? (float)paddleSprite.Width : paddleSprite.Width * Scale.X); } } public float Height { get { return ( Scale.Y==1f ? (float)paddleSprite.Height : paddleSprite.Height*Scale.Y ); } } public Texture2D GetSprite { get { return paddleSprite; } } public Rectangle Boundary { get { return new Rectangle((int)paddlePosition.X, (int)paddlePosition.Y, (int)this.Width, (int)this.Height); } } public bool KeyboardEnabled { get { return keybEnabled; } } #endregion private void NormalsToEdges(bool isLeftPaddle) { Normals2Edges = null; Edge = Vector2.Zero; lst.Clear(); for (int i = 0; i < Vertices.Length; i++) { Edge = Vertices[i + 1 == Vertices.Length ? 0 : i + 1] - Vertices[i]; if (Edge != Vector2.Zero) { Edge.Normalize(); //outer normal to edge !! (origin in top-left) lst.Add(new Vector2(Edge.Y, -Edge.X)); } } Normals2Edges = lst.ToArray(); } public float[] ProjectPaddle(Vector2 axis) { if (Vertices.Length == 0 || axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, Vertices[0]); max = min; for (int i = 1; i < Vertices.Length; i++) { float p = Vector2.Dot(axis, Vertices[i]); if (p < min) min = p; else if (p > max) max = p; } return (new float[2] { min, max }); } public Paddle(Game game, bool isLeftPaddle, bool enableKeyboard = true) : base(game) { contentManager = new ContentManager(game.Services); keybEnabled = enableKeyboard; this.isLeftPaddle = isLeftPaddle; } public void setPosition(Vector2 newPos) { X = newPos.X; Y = newPos.Y; } public override void Initialize() { base.Initialize(); this.Speed = DEFAULT_Y_SPEED; X = 0; Y = 0; NormalsToEdges(this.isLeftPaddle); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleSprite = contentManager.Load<Texture2D>(@"Content\pongBar"); } public override void Update(GameTime gameTime) { //vertices array Vertices[0] = this.paddlePosition; Vertices[1] = this.paddlePosition + new Vector2(this.Width, 0); Vertices[2] = this.paddlePosition + new Vector2(this.Width, this.Height); Vertices[3] = this.paddlePosition + new Vector2(0, this.Height); // Move paddle, but don't allow movement off the screen if (KeyboardEnabled) { float moveDistance = Speed * (float)gameTime.ElapsedGameTime.TotalSeconds; KeyboardState newKeyState = Keyboard.GetState(); if (newKeyState.IsKeyDown(Keys.Down) && Y + paddleSprite.Height + moveDistance <= Game.GraphicsDevice.Viewport.Height) { Y += moveDistance; } else if (newKeyState.IsKeyDown(Keys.Up) && Y - moveDistance >= 0) { Y -= moveDistance; } } else { if (this.Y + this.Height > this.GraphicsDevice.Viewport.Height) { this.Y = this.Game.GraphicsDevice.Viewport.Height - this.Height - 1; } } base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(SpriteSortMode.Texture,null); spriteBatch.Draw(paddleSprite, paddlePosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Ball Class public class Ball : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private const float DEFAULT_SPEED = 50; private float speedIncrement = 0; private Vector2 ballScale = new Vector2(1f, 1f); private const float INCREASE_SPEED = 50; private Texture2D ballSprite; //initial texture private Vector2 ballPosition; //position private Vector2 centerOfBall; //center coords private Vector2 ballSpeed = new Vector2(DEFAULT_SPEED, DEFAULT_SPEED); //speed #endregion #region Properties public float DEFAULTSPEED { get { return DEFAULT_SPEED; } } public Vector2 ballCenter { get { return centerOfBall; } } public Vector2 Scale { get { return ballScale; } set { ballScale = value; } } public float SpeedX { get { return ballSpeed.X; } set { ballSpeed.X = value; } } public float SpeedY { get { return ballSpeed.Y; } set { ballSpeed.Y = value; } } public float X { get { return ballPosition.X; } set { ballPosition.X = value; } } public float Y { get { return ballPosition.Y; } set { ballPosition.Y = value; } } public Texture2D GetSprite { get { return ballSprite; } } public float Width { get { return (Scale.X == 1f ? (float)ballSprite.Width : ballSprite.Width * Scale.X); } } public float Height { get { return (Scale.Y == 1f ? (float)ballSprite.Height : ballSprite.Height * Scale.Y); } } public float SpeedIncreaseIncrement { get { return speedIncrement; } set { speedIncrement = value; } } public Rectangle Boundary { get { return new Rectangle((int)ballPosition.X, (int)ballPosition.Y, (int)this.Width, (int)this.Height); } } #endregion public Ball(Game game) : base(game) { contentManager = new ContentManager(game.Services); } public void Reset() { ballSpeed.X = DEFAULT_SPEED; ballSpeed.Y = DEFAULT_SPEED; ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } public void SpeedUp() { if (ballSpeed.Y < 0) ballSpeed.Y -= (INCREASE_SPEED + speedIncrement); else ballSpeed.Y += (INCREASE_SPEED + speedIncrement); if (ballSpeed.X < 0) ballSpeed.X -= (INCREASE_SPEED + speedIncrement); else ballSpeed.X += (INCREASE_SPEED + speedIncrement); } public float[] ProjectBall(Vector2 axis) { if (axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, this.ballCenter) - this.Width/2; //center - radius max = min + this.Width; //center + radius return (new float[2] { min, max }); } public void ChangeHorzDirection() { ballSpeed.X *= -1; } public void ChangeVertDirection() { ballSpeed.Y *= -1; } public override void Initialize() { base.Initialize(); ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); ballSprite = contentManager.Load<Texture2D>(@"Content\ball"); } public override void Update(GameTime gameTime) { if (this.Y < 1 || this.Y > GraphicsDevice.Viewport.Height - this.Height - 1) this.ChangeVertDirection(); centerOfBall = new Vector2(ballPosition.X + this.Width / 2, ballPosition.Y + this.Height / 2); base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.Draw(ballSprite, ballPosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Main game class public class gameStart : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; public gameStart() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; this.Window.Title = "Pong game"; } protected override void Initialize() { ball = new Ball(this); paddleLeft = new Paddle(this,true,false); paddleRight = new Paddle(this,false,true); Components.Add(ball); Components.Add(paddleLeft); Components.Add(paddleRight); this.Window.AllowUserResizing = false; this.IsMouseVisible = true; this.IsFixedTimeStep = false; this.isColliding = false; base.Initialize(); } #region MyPrivateStuff private Ball ball; private Paddle paddleLeft, paddleRight; private int[] bit = { -1, 1 }; private Random rnd = new Random(); private int updates = 0; enum nrPaddle { None, Left, Right }; private nrPaddle PongBar = nrPaddle.None; private ArrayList Axes = new ArrayList(); private Vector2 MTV; //minimum translation vector private bool isColliding; private float overlap; //smallest distance after projections private Vector2 overlapAxis; //axis of overlap #endregion protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleLeft.setPosition(new Vector2(0, this.GraphicsDevice.Viewport.Height / 2 - paddleLeft.Height / 2)); paddleRight.setPosition(new Vector2(this.GraphicsDevice.Viewport.Width - paddleRight.Width, this.GraphicsDevice.Viewport.Height / 2 - paddleRight.Height / 2)); paddleLeft.Scale = new Vector2(1f, 2f); //scale left paddle } private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] <= circle[0] || circle[1] <= pad[0]) { return false; } if (pad[1] - circle[0] < circle[1] - pad[0]) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax; } } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * overlap; } return true; } protected override void Update(GameTime gameTime) { updates += 1; float ftime = 5 * (float)gameTime.ElapsedGameTime.TotalSeconds; if (updates == 1) { isColliding = false; int Xrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; int Yrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; ball.SpeedX = Xrnd * ball.SpeedX; ball.SpeedY = Yrnd * ball.SpeedY; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } else { updates = 100; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } //autorun :) paddleLeft.Y = ball.Y; //collision detection PongBar = nrPaddle.None; if (ball.Boundary.Intersects(paddleLeft.Boundary)) { PongBar = nrPaddle.Left; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleLeft.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleLeft.VertexVector, ball.ballCenter)); } } else if (ball.Boundary.Intersects(paddleRight.Boundary)) { PongBar = nrPaddle.Right; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleRight.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleRight.VertexVector, ball.ballCenter)); } } if (PongBar != nrPaddle.None && !isColliding) switch (PongBar) { case nrPaddle.Left: if (ShapesIntersect(paddleLeft, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; case nrPaddle.Right: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; default: break; } if (!ShapesIntersect(paddleRight, ball) && !ShapesIntersect(paddleLeft, ball)) isColliding = false; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; //check ball movement if (ball.X > paddleRight.X + paddleRight.Width + 2) { //IncreaseScore(Left); ball.Reset(); updates = 0; return; } else if (ball.X < paddleLeft.X - 2) { //IncreaseScore(Right); ball.Reset(); updates = 0; return; } base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Aquamarine); spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend); spriteBatch.End(); base.Draw(gameTime); } } And one method i've used: public static Vector2 NormAxisFromCircle2ClosestVertex(Vector2[] vertices, Vector2 circle) { Vector2 temp = Vector2.Zero; if (vertices.Length > 0) { float dist = (circle.X - vertices[0].X) * (circle.X - vertices[0].X) + (circle.Y - vertices[0].Y) * (circle.Y - vertices[0].Y); for (int i = 1; i < vertices.Length;i++) { if (dist > (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y)) { temp = vertices[i]; //memorize the closest vertex dist = (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y); } } temp = circle - temp; temp.Normalize(); } return temp; } Thanks in advance for any tips on the 4 issues. EDIT1: Something isn't working properly. The collision axis doesn't come out right and the interpolation also seems to have no effect. I've changed the code a bit: private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] < circle[0] || circle[1] < pad[0]) { return false; } if (Math.Abs(pad[1] - circle[0]) < Math.Abs(circle[1] - pad[0])) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax * (-1); } //to get the proper axis } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * Math.Abs(overlap); } return true; } And part of the Update method: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) { ball.X += MTV.X; ball.Y += MTV.Y; } //test if (overlapAxis.X == 0) //collision with horizontal edge { } else if (overlapAxis.Y == 0) //collision with vertical edge { float factor = Math.Abs(ball.ballCenter.Y - paddleRight.Y) / paddleRight.Height; if (factor > 1) factor = 1f; if (overlapAxis.X < 0) //left edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(-1, -3), new Vector2(-1, 3), factor)))); else //right edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(1, -3), new Vector2(1, 3), factor)))); } else //vertex collision??? { ball.Speed = -ball.Speed; } } What seems to happen is that "overlapAxis" doesn't always return the right one. So instead of (-1,0) i get the (1,0) (this happened even before i multiplied with -1 there). Sometimes there isn't even a collision registered even though the ball passes through the paddle... The interpolation also seems to have no effect as the angles barely change (or the overlapAxis is almost never (-1,0) or (1,0) but something like (0.9783473, 0.02743843)... ). What am i missing here? :(

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• Sphere Texture Mapping shows visible seams

  - by AvengerDr

  As you can see from the above picture there is a visible seam in the texture mapping. The underlying mesh is a geosphere based on octahedron subdivisions. On that particular latitude, vertices have been duplicated. However there still is a visible seam. Here is how I calculate the UV coordinates: float longitude = (float)Math.Atan2(normal.X, -normal.Z); float latitude = (float)Math.Acos(normal.Y); float u = (float)(longitude / (Math.PI * 2.0) + 0.5); float v = (float)(latitude / Math.PI); Is this a problem in the coordinates or a mipmapping issue?

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• Why does my sprite glitch when moving? [closed]

  - by rphello101

  Using Slick 2D/Java, I'm using the mouse to rotate a sprite and WASD to move it (A and D are used to strafe). I finally got the directional keys and rotation to work in sync, but I'm having problems with sporadic movement. It seems that the move speed is not always set to the value I have it at. Sometimes the sprite with just shoot across the screen. Furthermore, it seems that at 0 degrees, when the left key is pressed, the sprite moves backwards, not to the left. There also seems to be quite a bit of glitching when two keys are pressed, like left and up. Anyone see anything obvious? Here is the rotational code: int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x+sprite.image.getWidth()/2; int pY = sprite.y+sprite.image.getHeight()/2; double mAng; if(mX!=pX){ mAng = Math.toDegrees(Math.atan2(mY - pY, mX - pX)); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=90; else mAng=270; } sprite.angle = mAng; sprite.image.setRotation((float) mAng); Movement code: Input input = gc.getInput(); Vector2f direction = new Vector2f(); Vector2f velocity = new Vector2f(); Vector2f left; Vector2f right; direction.x = (float) Math.cos(Math.toRadians(sprite.angle)); direction.y = (float) Math.sin(Math.toRadians(sprite.angle)); if(direction.length()>0) direction = direction.normalise(); left = new Vector2f(-direction.y, direction.x); right = new Vector2f(direction.y, -direction.x); velocity.x = (float) (direction.x * sprite.moveSpeed); velocity.y = (float) (direction.y * sprite.moveSpeed); if(input.isKeyDown(sprite.up)){ sprite.x += velocity.x*delta; sprite.y += velocity.y*delta; }if (input.isKeyDown(sprite.down)){ sprite.x -= velocity.x*delta; sprite.y -= velocity.y*delta; }if (input.isKeyDown(sprite.left)){ sprite.x += left.x * sprite.moveSpeed * delta; sprite.y += left.y * sprite.moveSpeed * delta; }if (input.isKeyDown(sprite.right)){ sprite.x += right.x * sprite.moveSpeed * delta; sprite.y += right.y * sprite.moveSpeed * delta; }

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• x axis detection issues platformer starter kit

  - by dbomb101

  I've come across a problem with the collision detection code in the platformer starter kit for xna.It will send up the impassible flag on the x axis despite being nowhere near a wall in either direction on the x axis, could someone could tell me why this happens ? Here is the collision method. /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, TileCollision collision = Level.GetCollision(x, y); if (collision != TileCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == TileCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == TileCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } //This is the section which deals with collision on the x-axis else if (collision == TileCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; }

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• Platformer Starter Kit - Collision Issues

  - by Cyral

  I'm having trouble with my game that is based off the XNA Platformer starter kit. My game uses smaller tiles (16x16) then the original (32x40) which I'm thinking may be having an effect on collision (Being it needs to be more precise). Standing on the edge of a tile and jumping causes the player to move off the the tile when he lands. And 80% of the time, when the player lands, he goes flying though SOLID tiles in a diagonal fashion. This is very annoying as it is almost impossible to test other features, when spawning and jumping will result in the player landing in another part of the level or falling off the edge completely. The code is as follows: /// <summary> /// Updates the player's velocity and position based on input, gravity, etc. /// </summary> public void ApplyPhysics(GameTime gameTime) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; Vector2 previousPosition = Position; // Base velocity is a combination of horizontal movement control and // acceleration downward due to gravity. velocity.X += movement * MoveAcceleration * elapsed; velocity.Y = MathHelper.Clamp(velocity.Y + GravityAcceleration * elapsed, -MaxFallSpeed, MaxFallSpeed); velocity.Y = DoJump(velocity.Y, gameTime); // Apply pseudo-drag horizontally. if (IsOnGround) velocity.X *= GroundDragFactor; else velocity.X *= AirDragFactor; // Prevent the player from running faster than his top speed. velocity.X = MathHelper.Clamp(velocity.X, -MaxMoveSpeed, MaxMoveSpeed); // Apply velocity. Position += velocity * elapsed; Position = new Vector2((float)Math.Round(Position.X), (float)Math.Round(Position.Y)); // If the player is now colliding with the level, separate them. HandleCollisions(); // If the collision stopped us from moving, reset the velocity to zero. if (Position.X == previousPosition.X) velocity.X = 0; if (Position.Y == previousPosition.Y) velocity.Y = 0; } /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, ItemCollision collision = Level.GetCollision(x, y); if (collision != ItemCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == ItemCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == ItemCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } else if (collision == ItemCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; } It also tends to jitter a little bit sometimes, I'm solved some of this with some fixes I found here on stackexchange, But Ive only seen one other case of the flying though blocks problem. This question seems to have a similar problem in the video, but mine is more crazy. Again this is a very annoying bug! Any help would be greatly appreciated! EDIT: Speed stuff // Constants for controling horizontal movement private const float MoveAcceleration = 13000.0f; private const float MaxMoveSpeed = 1750.0f; private const float GroundDragFactor = 0.48f; private const float AirDragFactor = 0.58f; // Constants for controlling vertical movement private const float MaxJumpTime = 0.35f; private const float JumpLaunchVelocity = -3500.0f; private const float GravityAcceleration = 3400.0f; private const float MaxFallSpeed = 550.0f; private const float JumpControlPower = 0.14f;

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• Joystick example problem for android 2D

  - by iQue

  I've searched all over the web for an answer to this, and there are simular topics but nothing works for me, and I have no Idea why. I just want to move my sprite using a joystick, since I'm useless at math when it comes to angles etc I used an example, Ill post the code here: public float initx = 50; //og 425; public float inity = 300; //og 267; public Point _touchingPoint = new Point(50, 300); //og(425, 267); public Point _pointerPosition = new Point(100, 170); private Boolean _dragging = false; private MotionEvent lastEvent; @Override public boolean onTouchEvent(MotionEvent event) { if (event == null && lastEvent == null) { return _dragging; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } // drag drop if (event.getAction() == MotionEvent.ACTION_DOWN) { _dragging = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { _dragging = false; } if (_dragging) { // get the pos _touchingPoint.x = (int) event.getX(); _touchingPoint.y = (int) event.getY(); // bound to a box if (_touchingPoint.x < 25) { _touchingPoint.x = 25; //og 400 } if (_touchingPoint.x > 75) { _touchingPoint.x = 75; //og 450 } if (_touchingPoint.y < 275) { _touchingPoint.y = 275; //og 240 } if (_touchingPoint.y > 325) { _touchingPoint.y = 325; //og 290 } // get the angle double angle = Math.atan2(_touchingPoint.y - inity, _touchingPoint.x - initx) / (Math.PI / 180); // Move the beetle in proportion to how far // the joystick is dragged from its center _pointerPosition.y += Math.sin(angle * (Math.PI / 180)) * (_touchingPoint.x / 70); _pointerPosition.x += Math.cos(angle * (Math.PI / 180)) * (_touchingPoint.x / 70); // stop the sprite from goin thru if (_pointerPosition.x + happy.getWidth() >= getWidth()) { _pointerPosition.x = getWidth() - happy.getWidth(); } if (_pointerPosition.x < 0) { _pointerPosition.x = 0; } if (_pointerPosition.y + happy.getHeight() >= getHeight()) { _pointerPosition.y = getHeight() - happy.getHeight(); } if (_pointerPosition.y < 0) { _pointerPosition.y = 0; } } public void render(Canvas canvas) { canvas.drawColor(Color.BLUE); canvas.drawBitmap(joystick.get_joystickBg(), initx-45, inity-45, null); canvas.drawBitmap(happy, _pointerPosition.x, _pointerPosition.y, null); canvas.drawBitmap(joystick.get_joystick(), _touchingPoint.x - 26, _touchingPoint.y - 26, null); } public void update() { this.onTouchEvent(null); } og= original position. as you can see Im trying to move the joystick, but when I do it stops working correctly, I mean it still works like a joystick but the sprite dosnt move accordingly, if I for example push the joystick down, the sprite moves up, and if I push it up it moves left. can anyone PLEASE help me, I've been stuck here for sooo long and its really frustrating.

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• Java - Tile engine changing number in array not changing texture

  - by Corey

  I draw my map from a txt file. Would I have to write to the text file to notice the changes I made? Right now it changes the number in the array but the tile texture doesn't change. Do I have to do more than just change the number in the array? public class Tiles { public Image[] tiles = new Image[5]; public int[][] map = new int[64][64]; private Image grass, dirt, fence, mound; private SpriteSheet tileSheet; public int tileWidth = 32; public int tileHeight = 32; Player player = new Player(); public void init() throws IOException, SlickException { tileSheet = new SpriteSheet("assets/tiles.png", tileWidth, tileHeight); grass = tileSheet.getSprite(0, 0); dirt = tileSheet.getSprite(7, 7); fence = tileSheet.getSprite(2, 0); mound = tileSheet.getSprite(2, 6); tiles[0] = grass; tiles[1] = dirt; tiles[2] = fence; tiles[3] = mound; int x=0, y=0; BufferedReader in = new BufferedReader(new FileReader("assets/map.dat")); String line; while ((line = in.readLine()) != null) { String[] values = line.split(","); for (String str : values) { int str_int = Integer.parseInt(str); map[x][y]=str_int; //System.out.print(map[x][y] + " "); y=y+1; } //System.out.println(""); x=x+1; y = 0; } in.close(); } public void update(GameContainer gc) { } public void render(GameContainer gc) { for(int x = 0; x < map.length; x++) { for(int y = 0; y < map.length; y ++) { int textureIndex = map[y][x]; Image texture = tiles[textureIndex]; texture.draw(x*tileWidth,y*tileHeight); } } } Mouse picking public void checkDistance(GameContainer gc) { Input input = gc.getInput(); float mouseX = input.getMouseX(); float mouseY = input.getMouseY(); double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { System.out.println("Clicked"); if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } System.out.println(tiles.map[(int)mousetileX][(int)mousetileY]); }

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• HTG Explains: What Are Computer Algorithms and How Do They Work?

  - by YatriTrivedi

    Unless you’re into math or programming, the word “algorithm” might be Greek to you, but it’s one of the building blocks of everything you’re using to read this article. Here’s a quick explanation of what they are, and how they work. Disclaimer: I’m not a math or computer science teacher, so not all of the terms I use are technical. That’s because I’m trying to explain everything in plain English for people aren’t quite comfortable with math. That being said, there is some math involved, and that’s unavoidable. Math geeks, feel free to correct or better explain in the comments, but please, keep it simple for the mathematically disinclined among us. Image by Ian Ruotsala Latest Features How-To Geek ETC How To Make Hundreds of Complex Photo Edits in Seconds With Photoshop Actions How to Enable User-Specific Wireless Networks in Windows 7 How to Use Google Chrome as Your Default PDF Reader (the Easy Way) How To Remove People and Objects From Photographs In Photoshop Ask How-To Geek: How Can I Monitor My Bandwidth Usage? Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Lucky Kid Gets Playable Angry Birds Cake [Video] See the Lord of the Rings Epic from the Perspective of Mordor [eBook] Smart Taskbar Is a Thumb Friendly Android Task Launcher Comix is an Awesome Comics Archive Viewer for Linux Get the MakeUseOf eBook Guide to Speeding Up Windows for Free Need Tech Support? Call the Star Wars Help Desk! [Video Classic]

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• Sound Channel map incorrect on an ION 330 ASRock

  - by math

  I have a ION 330 ASRock just updated on Precise and the sound channel mapping is incorrect. Channel map is set as follow: Front Left = Front left Center = Rear Left Front Right = Font Right Rear Right = LFE Rear Left = Center LFE = Rear Right I am testing the sound channel using speaker-test -c 2 -t wav Can some one tell me how I can remap easily? I have tried several possible changes to /etc/pulse/defaut.pa unsuccessfully.

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• Resultant Vector Algorithm for 2D Collisions

  - by John

  I am making a Pong based game where a puck hits a paddle and bounces off. Both the puck and the paddles are Circles. I came up with an algorithm to calculate the resultant vector of the puck once it meets a paddle. The game seems to function correctly but I'm not entirely sure my algorithm is correct. Here are my variables for the algorithm: Given: velocity = the magnitude of the initial velocity of the puck before the collision x = the x coordinate of the puck y = the y coordinate of the puck moveX = the horizontal speed of the puck moveY = the vertical speed of the puck otherX = the x coordinate of the paddle otherY = the y coordinate of the paddle piece.horizontalMomentum = the horizontal speed of the paddle before it hits the puck piece.verticalMomentum = the vertical speed of the paddle before it hits the puck slope = the direction, in radians, of the puck's velocity distX = the horizontal distance between the center of the puck and the center of the paddle distY = the vertical distance between the center of the puck and the center of the paddle Algorithm solves for: impactAngle = the angle, in radians, of the angle of impact. newSpeedX = the speed of the resultant vector in the X direction newSpeedY = the speed of the resultant vector in the Y direction Here is the code for my algorithm: int otherX = piece.x; int otherY = piece.y; double velocity = Math.sqrt((moveX * moveX) + (moveY * moveY)); double slope = Math.atan(moveX / moveY); int distX = x - otherX; int distY = y - otherY; double impactAngle = Math.atan(distX / distY); double newAngle = impactAngle + slope; int newSpeedX = (int)(velocity * Math.sin(newAngle)) + piece.horizontalMomentum; int newSpeedY = (int)(velocity * Math.cos(newAngle)) + piece.verticalMomentum; for those who are not program savvy here is it simplified: velocity = v(moveX² + moveY²) slope = arctan(moveX / moveY) distX = x - otherX distY = y - otherY impactAngle = arctan(distX / distY) newAngle = impactAngle + slope newSpeedX = velocity * sin(newAngle) + piece.horizontalMomentum newSpeedY = velocity * cos(newAngle) + piece.verticalMomentum My Question: Is this algorithm correct? Is there an easier/simpler way to do what I'm trying to do?

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• Improving the Performance of the Secure Hash Algorithm (SHA-1)

  Parallelization can make a difference Algorithm - Math - Cryptography - Communication Theory - Parallel computing

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• Euler angles to Cartesian Coordinates for use with gluLookAt

  - by notrodash

  I have searched all of the internet but just couldn't find the answer. I am using LibGDX and this is part of my code that loops over and over: public void render() { GL11 gl = Gdx.gl11; float centerX = (float)Math.cos(yaw) * (float)Math.cos(pitch); float centerY = (float)Math.sin(yaw) * (float)Math.cos(pitch); float centerZ = (float)Math.sin(pitch); System.out.println(centerX+" "+centerY+" "+centerZ+" ~ "+GDXRacing.camera.position.x+" "+GDXRacing.camera.position.y+" "+GDXRacing.camera.position.z); Gdx.glu.gluLookAt(gl, GDXRacing.camera.position.x, GDXRacing.camera.position.y, GDXRacing.camera.position.z, centerX, centerY, centerZ, 0, 1, 0); if(Gdx.input.isKeyPressed(Keys.A)) { yaw--; } if(Gdx.input.isKeyPressed(Keys.D)) { yaw++; } } I might just be bad at the math, but I dont get it. Does someone have a good explanation and an idea about how to deal with this? I am trying to make a first person camera. By the way, the camera is translated by +10 on the Z axis. Currently when I run the application, this is what I get: Watch video in browser | Download video (for those who cant download the video, everything shakes in a clockwise/anticlockwise action, depending on if I increase or decrease the Yaw value) -Thank you. [edit] and with this code: public void render() { GL11 gl = Gdx.gl11; float centerX = (float)(MathUtils.cosDeg(yaw)*4); float centerY = 0; float centerZ = (float)(MathUtils.sinDeg(yaw)*4); System.out.println(centerX+" "+centerY+" "+centerZ+" ~ "+GDXRacing.camera.position.x+" "+GDXRacing.camera.position.y+" "+GDXRacing.camera.position.z); Gdx.glu.gluLookAt(gl, GDXRacing.camera.position.x, GDXRacing.camera.position.y, GDXRacing.camera.position.z, centerX, centerY, centerZ, 0, 1, 0); if(Gdx.input.isKeyPressed(Keys.A)) { yaw--; } if(Gdx.input.isKeyPressed(Keys.D)) { yaw++; } } it slowly swings from the left to the right. This approach worked for turning left and right for 2d games though. What am I doing wrong?

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• Precision loss when transforming from cartesian to isometric

  - by Justin Skiles

  My goal is to display a tile map in isometric projection. This tile map has 25 tiles across and 25 tiles down. Each tile is 32x32. See below for how I'm accomplishing this. World Space World Space to Screen Space Rotation (45 degrees) Using a 2D rotation matrix, I use the following: double rotation = Math.PI / 4; double rotatedX = ((tileWorldX * Math.Cos(rotation)) - ((tileWorldY * Math.Sin(rotation))); double rotatedY = ((tileWorldX * Math.Sin(rotation)) + (tileWorldY * Math.Cos(rotation))); World Space to Screen Space Scale (Y-axis reduced by 50%) Here I simply scale down the Y value by a factor of 0.5. Problem And it works, kind of. There are some tiny 1px-2px gaps between some of the tiles when rendering. I think there's some precision loss somewhere, or I'm not understanding how to get these tiles to fit together perfectly. I'm not truncating or converting my values to non-decimal types until I absolutely have to (when I pass to the render method, which only takes integers). I'm not sure how to guarantee pixel perfect rendering precision when I'm rotating and scaling on a level of higher precision. Any advice? Do I need to supply for information?

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• How can I set a time limit for a game?

  - by Haoda Fu

  I am learning the multi-threading and timer in C# now. But it seems I can't find a good solution. For example, I would like to see how many addition problems that I can solve within 1 min. I would like my program to have A digital clock to count for 60 seconds in the top of my Console. Print a math problem in the middle of my console wait for my input. When 60 seconds is done, stop the math problem challenges immediately (most of time, it is still waiting for my input, but we will stop it immediately). Count how many correct problems that I have solved. Two challenges of the program now. a) how can we make sure the print time and math problem do not mess up. b) how can we stop the math challenges part immediately after time is up

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• Designing Parallel Algorithms: Part 5

  Case Study: Floorplan Optimization Algorithm - Parallel computing - Math - Combinatorics - People

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• C# Collision test of a ship and asteriod, angle confusion

  - by Cherry

  We are trying to to do a collision detection for the ship and asteroid. If success than it should detect the collision before N turns. However it is confused between angle 350 and 15 and it is not really working. Sometimes it is moving but sometime it is not moving at all. On the other hand, it is not shooting at the right time as well. I just want to ask how to make the collision detection working??? And how to solve the angle confusion problem? // Get velocities of asteroid Console.WriteLine("lol"); // IF equation is between -2 and -3 if (equation1a <= -2) { // Calculate no. turns till asteroid hits float turns_till_hit = dx / vx; // Calculate angle of asteroid float asteroid_angle_rad = (float)Math.Atan(Math.Abs(dy / dx)); float asteroid_angle_deg = (float)(asteroid_angle_rad * 180 / Math.PI); float asteroid_angle = 0; // Calculate angle if asteroid is in certain positions if (asteroid.Y > ship.Y && asteroid.X > ship.X) { asteroid_angle = asteroid_angle_deg; } else if (asteroid.Y < ship.Y && asteroid.X > ship.X) { asteroid_angle = (360 - asteroid_angle_deg); } else if (asteroid.Y < ship.Y && asteroid.X < ship.X) { asteroid_angle = (180 + asteroid_angle_deg); } else if (asteroid.Y > ship.Y && asteroid.X < ship.X) { asteroid_angle = (180 - asteroid_angle_deg); } // IF turns till asteroid hits are less than 35 if (turns_till_hit < 50) { float angle_between = 0; // Calculate angle between if asteroid is in certain positions if (asteroid.Y > ship.Y && asteroid.X > ship.X) { angle_between = ship_angle - asteroid_angle; } else if (asteroid.Y < ship.Y && asteroid.X > ship.X) { angle_between = (360 - Math.Abs(ship_angle - asteroid_angle)); } else if (asteroid.Y < ship.Y && asteroid.X < ship.X) { angle_between = ship_angle - asteroid_angle; } else if (asteroid.Y > ship.Y && asteroid.X < ship.X) { angle_between = ship_angle - asteroid_angle; } // If angle less than 0, add 360 if (angle_between < 0) { //angle_between %= 360; angle_between = Math.Abs(angle_between); } // Calculate no. of turns to face asteroid float turns_to_face = angle_between / 25; if (turns_to_face < turns_till_hit) { float ship_angle_left = ShipAngle(ship_angle, "leftKey", 1); float ship_angle_right = ShipAngle(ship_angle, "rightKey", 1); float angle_between_left = Math.Abs(ship_angle_left - asteroid_angle); float angle_between_right = Math.Abs(ship_angle_right - asteroid_angle); if (angle_between_left < angle_between_right) { leftKey = true; } else if (angle_between_right < angle_between_left) { rightKey = true; } } if (angle_between > 0 && angle_between < 25) { spaceKey = true; } } }

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