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• Performance issues with visibility detection and object transparency

  - by maul

  I'm working on a 3d game that has a view similar to classic isometric games (diablo, etc.). One of the things I'm trying to implement is the effect of turning walls transparent when the player walks behind them. By itself this is not a huge issue, but I'm having trouble determining which walls should be transparent exactly. I can't use a circle or square mask. There are a lot of cases where the wall piece at the same (relative) position has different visibility depending on the surrounding area. With the help of a friend I came up with this algorithm: Create a grid around the player that contains a lot of "visibility points" (my game is semi tile-based so I create one point for every tile on the grid) - the size of the square's side is close to the radius where I make objects transparent. I found 6x6 to be a good value, so that's 36 visibility points total. For every visibility point on the grid, check if that point is in the player's line of sight. For every visibility point that is in the LOS, cast a ray from the camera to that point and mark all objects the ray hits as transparent. This algorithm works - not perfectly, but only requires some tuning - however this is very slow. As you can see, it requries 36 ray casts minimum, but most of the time 60-70 depending on the position. That's simply too much for the CPU. Is there a better way to do this? I'm using Unity 3D but I'm not looking for an engine-specific solution.

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• How to connect Ethernet on Ubuntu (with auto-detection)

  - by user12285

  It's been well over six months but I have the same router SmartAX MT880d with Ethernet, and the exact same problem : no internet, even though I can successfully reach the modem settings page by entering 192.168.1.1 in Firefox. I'm a total beginner with Ubuntu. My internet works great in Windows but does not work in Ubuntu. Sorry if I don't use the right (technical) terminology to explain my issue. English is not my mother tongue. For 2 weeks, I've been doing reading on the web and forums and the ubuntuguide.org to name a few, but to no avail. Now I see no other solution but to ask for help. My problem is that I can't find a way to put the right digits in the right place because I don't know what numbers I need to put in what files. E.g.: do I need to use DHCP? or a static IP address? No clue whatsoever. I'm concerned that I might put figures in the wrong spaces. For example, is the modem/router's IP exactly 192.168.1.1 for Huawei Smart AXMT880d modem? Is the subnet 255.255.255.0? Gateway 192.168.1.1? I'm confused as I can also see a different IP starting with 155131*** (is it an account number?) on my contract with Huawei (a Chinese ISP). Apart from calling 911, what other numbers do I need to put in and where? How do I check that all the numbers have been entered correctly in every appropriate space before trying to connect the Internet?

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• Object detection in bitmap JavaScript canvas

  - by fallenAngel

  I want to detect clicks on canvas elements which are drawn using paths. So far I have stored element paths in a JavaScript data structure and then check the coordinates of hits which match the element's coordinates. Rendering each element path and checking the hits would be inefficient when there are a lot of elements. I believe there must be an algorithm for this kind of coordinate search, can anyone help me with this?

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• Keypress detection wont work after seemingly unrelated code change

  - by LukeZaz

  I'm trying to have the Enter key cause a new 'map' to generate for my game, but for whatever reason after implementing full-screen in it the input check won't work anymore. I tried removing the new code and only pressing one key at a time, but it still won't work. Here's the check code and the method it uses, along with the newMap method: public class Game1 : Microsoft.Xna.Framework.Game { // ... protected override void Update(GameTime gameTime) { // ... // Check if Enter was pressed - if so, generate a new map if (CheckInput(Keys.Enter, 1)) { blocks = newMap(map, blocks, console); } // ... } // Method: Checks if a key is/was pressed public bool CheckInput(Keys key, int checkType) { // Get current keyboard state KeyboardState newState = Keyboard.GetState(); bool retType = false; // Return type if (checkType == 0) { // Check Type: Is key currently down? if (newState.IsKeyDown(key)) { retType = true; } else { retType = false; } } else if (checkType == 1) { // Check Type: Was the key pressed? if (newState.IsKeyDown(key)) { if (!oldState.IsKeyDown(key)) { // Key was just pressed retType = true; } else { // Key was already pressed, return false retType = false; } } } // Save keyboard state oldState = newState; // Return result if (retType == true) { return true; } else { return false; } } // Method: Generate a new map public List<Block> newMap(Map map, List<Block> blockList, Console console) { // Create new map block coordinates List<Vector2> positions = new List<Vector2>(); positions = map.generateMap(console); // Clear list and reallocate memory previously used up by it blockList.Clear(); blockList.TrimExcess(); // Add new blocks to the list using positions created by generateMap() foreach (Vector2 pos in positions) { blockList.Add(new Block() { Position = pos, Texture = dirtTex }); } // Return modified list return blockList; } // ... } and the generateMap code: // Generate a list of Vector2 positions for blocks public List<Vector2> generateMap(Console console, int method = 0) { ScreenTileWidth = gDevice.Viewport.Width / 16; ScreenTileHeight = gDevice.Viewport.Height / 16; maxHeight = gDevice.Viewport.Height; List<Vector2> blockLocations = new List<Vector2>(); if (useScreenSize == true) { Width = ScreenTileWidth; Height = ScreenTileHeight; } else { maxHeight = Height; } int startHeight = -500; // For debugging purposes, the startHeight is set to an // hopefully-unreachable value - if it returns this, something is wrong // Methods of land generation /// <summary> /// Third version land generation /// Generates a base land height as the second version does /// but also generates a 'max change' value which determines how much /// the land can raise or lower by which it now does by a random amount /// during generation /// </summary> if (method == 0) { // Get the land height startHeight = rnd.Next(1, maxHeight); int maxChange = rnd.Next(1, 5); // Amount ground will raise/lower by int curHeight = startHeight; for (int w = 0; w < Width; w++) { // Run a chance to lower/raise ground level int changeBy = rnd.Next(1, maxChange); int doChange = rnd.Next(0, 3); if (doChange == 1 && !(curHeight <= (1 + maxChange))) { curHeight = curHeight - changeBy; } else if (doChange == 2 && !(curHeight >= (29 - maxChange))) { curHeight = curHeight + changeBy; } for (int h = curHeight; h < Height; h++) { // Location variables float x = w * 16; float y = h * 16; blockLocations.Add(new Vector2(x, y)); } } console.newMsg("[INFO] Cur, height change maximum: " + maxChange.ToString()); } /// <summary> /// Second version land generator /// Generates a solid mass of land starting at a random height /// derived from either screen height or provided height value /// </summary> else if (method == 1) { // Get the land height startHeight = rnd.Next(0, 30); for (int w = 0; w < Width; w++) { for (int h = startHeight; h < ScreenTileHeight; h++) { // Location variables float x = w * 16; float y = h * 16; // Add a tile at set location blockLocations.Add(new Vector2(x, y)); } } } /// <summary> /// First version land generator /// Generates land completely randomly either across screen or /// in a box set by Width and Height values /// </summary> else { // For each tile in the map... for (int w = 0; w < Width; w++) { for (int h = 0; h < Height; h++) { // Location variables float x = w * 16; float y = h * 16; // ...decide whether or not to place a tile... if (rnd.Next(0, 2) == 1) { // ...and if so, add a tile at that location. blockLocations.Add(new Vector2(x, y)); } } } } console.newMsg("[INFO] Cur, base height: " + startHeight.ToString()); return blockLocations; } I never touched any of the above code for this when it broke - changing keys won't seem to fix it. Despite this, I have camera movement set inside another Game1 method that uses WASD and works perfectly. All I did was add a few lines of code here: private int BackBufferWidth = 1280; // Added these variables private int BackBufferHeight = 800; public Game1() { graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = BackBufferWidth; // and this graphics.PreferredBackBufferHeight = BackBufferHeight; // this Content.RootDirectory = "Content"; this.graphics.IsFullScreen = true; // and this } When I try adding a console line to be printed in the event the key is pressed, it seems that the If is never even triggered despite the correct key being pressed.

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• Mobile phone detection (brand, model, browser etc)

  - by SyaZ

  What do you use to detect visitor's mobile phone, down to the model if possible? Currently we maintain our own database but it's really getting behind due to lack of manpower to maintain it, so we decided to give 3rd party solution a try. These are my candidates but I don't have time to really try them all: DeviceAtlas - 1 year personal evaluation, but basic license is affordable. Their database look solid with daily update and user-contributed tests / updates. I am favoring this one at the moment. DetectRight - I was recommended this by a colleague but really can't find much from their site. 20k devices -- really? WURFL - Open source, database collaboratively derived from UAProf. So basically if you're going with UAProf solution, you're better off with WURFL. DetectMoBileBrowsers - This looks like the simplest of all. Too bad it's language dependent (PHP). Please share your experience or suggestions!

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• object detection in bitmmap javacanvas

  - by user1538127

  i want to detect clicks on canvas elements which are drawn using paths. so far i have think of to store elements path in javascript data structure and then check the cordinates of hits which matches the elements cordinates. i belive there is algorithm already for thins kind o cordinate search. rendering each of element path and checking the hits would be inefficient when elements number is larger. can anyone point on me that?

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• collision detection problems - Javascript/canvas game

  - by Tom Burman

  Ok here is a more detailed version of my question. What i want to do: i simply want the have a 2d array to represent my game map. i want a player sprite and i want that sprite to be able to move around my map freely using the keyboard and also have collisions with certain tiles of my map array. i want to use very large maps so i need a viewport. What i have: I have a loop to load the tile images into an array: /Loop to load tile images into an array var mapTiles = []; for (x = 0; x <= 256; x++) { var imageObj = new Image(); // new instance for each image imageObj.src = "images/prototype/"+x+".jpg"; mapTiles.push(imageObj); } I have a 2d array for my game map: //Array to hold map data var board = [ [1,2,3,4,3,4,3,4,5,6,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [17,18,19,20,19,20,19,20,21,22,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [33,34,35,36,35,36,35,36,37,38,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [49,50,51,52,51,52,51,52,53,54,1,1,1,1,1,1,1,1,1,1,1,1,1,197,198,199,1,1,1,1], [65,66,67,68,146,147,67,68,69,70,1,1,1,1,1,1,1,1,216,217,1,1,1,213,214,215,1,1,1,1], [81,82,83,161,162,163,164,84,85,86,1,1,1,1,1,1,1,1,232,233,1,1,1,229,230,231,1,1,1,1], [97,98,99,177,178,179,180,100,101,102,1,1,1,1,59,1,1,1,248,249,1,1,1,245,246,247,1,1,1,1], [1,1,238,1,1,1,1,239,240,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [216,217,254,1,1,1,1,255,256,1,204,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [232,233,1,1,1,117,118,1,1,1,220,1,1,119,120,1,1,1,1,1,1,1,1,1,1,1,119,120,1,1], [248,249,1,1,1,133,134,1,1,1,1,1,1,135,136,1,1,1,1,1,1,59,1,1,1,1,135,136,1,1], [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,216,217,1,1,1,1,1,1,60,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,232,233,1,1,1,1,1,1,1,1,1,1,1,1,1,1,204,1,1,1,1,1,1,1,1,1,1,1], [1,1,248,249,1,1,1,1,1,1,1,1,1,1,1,1,1,1,220,1,1,1,1,1,1,216,217,1,1,1], [1,1,1,1,1,1,1,1,1,1,1,1,149,150,151,1,1,1,1,1,1,1,1,1,1,232,233,1,1,1], [12,12,12,12,12,12,12,13,1,1,1,1,165,166,167,1,1,1,1,1,1,119,120,1,1,248,249,1,1,1], [28,28,28,28,28,28,28,29,1,1,1,1,181,182,183,1,1,1,1,1,1,135,136,1,1,1,1,1,1,1], [44,44,44,44,44,15,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,59,1,1,197,198,199,1,1,1,1,119,120,1], [1,1,1,1,1,27,28,29,1,1,216,217,1,1,1,1,1,1,1,1,213,214,215,1,1,1,1,135,136,1], [1,1,1,1,1,27,28,29,1,1,232,233,1,1,1,1,1,1,1,1,229,230,231,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,248,249,1,1,1,1,1,1,1,1,245,246,247,1,1,1,1,1,1,1], [1,1,1,197,198,199,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,213,214,215,28,29,1,1,1,1,1,60,1,1,1,1,204,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,229,230,231,28,29,1,1,1,1,1,1,1,1,1,1,220,1,1,1,1,119,120,1,1,1,1,1], [1,1,1,245,246,247,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,135,136,1,1,60,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1] ]; I have my loop to place the correct tile sin the correct positions: //Loop to place tiles onto screen in correct position for (x = 0; x <= viewWidth; x++){ for (y = 0; y <= viewHeight; y++){ var width = 32; var height = 32; context.drawImage(mapTiles[board[y+viewY][x+viewX]],x*width, y*height); } } I Have my player object : //Place player object context.drawImage(playerImg, (playerX-viewX)*32,(playerY-viewY)*32, 32, 32); I have my viewport setup: //Set viewport pos viewX = playerX - Math.floor(0.5 * viewWidth); if (viewX < 0) viewX = 0; if (viewX+viewWidth > worldWidth) viewX = worldWidth - viewWidth; viewY = playerY - Math.floor(0.5 * viewHeight); if (viewY < 0) viewY = 0; if (viewY+viewHeight > worldHeight) viewY = worldHeight - viewHeight; I have my player movement: canvas.addEventListener('keydown', function(e) { console.log(e); var key = null; switch (e.which) { case 37: // Left if (playerY > 0) playerY--; break; case 38: // Up if (playerX > 0) playerX--; break; case 39: // Right if (playerY < worldWidth) playerY++; break; case 40: // Down if (playerX < worldHeight) playerX++; break; } My Problem: I have my map loading an it looks fine, but my player position thinks it's on a different tile to what it actually is. So for instance, i know that if my player moves left 1 tile, the value of that tile should be 2, but if i print out the value it should be moving to (2), it comes up with a different value. How ive tried to solve the problem: I have tried swap X and Y values for the initialization of my player, for when my map prints. If i swap the x and y values in this part of my code: context.drawImage(mapTiles[board[y+viewY][x+viewX]],x*width, y*height); The map doesnt get draw correctly at all and tiles are placed all in random positions or orientations IF i sway the x and y values for my player in this line : context.drawImage(playerImg, (playerX-viewX)*32,(playerY-viewY)*32, 32, 32); The players movements are inversed, so up and down keys move my player left and right viceversa. My question: Where am i going wrong in my code, and how do i solve it so i have my map looking like it should and my player moving as it should as well as my player returning the correct tileID it is standing on or moving too. Thanks Again ALSO Here is a link to my whole code: prototype

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• Why my collision detection is not accurate?

  - by optimisez

  After trying and trying, I still cannot understand why the leg of character exceeds the wall but no clipping issue when I hit the wall from below. How should I fix it to make him standstill on the wall? void initPlayer() { // Create texture. hr = D3DXCreateTextureFromFileEx(d3dDevice, "player.png", 169, 44, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), NULL, NULL, &player); playerRect.left = playerRect.top = 0; playerRect.right = 29; playerRect.bottom = 36; playerDest.X = 0; playerDest.Y = 564; playerDest.length = playerRect.right - playerRect.left; playerDest.height = playerRect.bottom - playerRect.top; } void initBox() { hr = D3DXCreateTextureFromFileEx(d3dDevice, "brock.png", 330, 132, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), NULL, NULL, &box); boxRect.left = 33; boxRect.top = 0; boxRect.right = 63; boxRect.bottom = 30; boxDest.X = boxDest.Y = 300; boxDest.length = boxRect.right - boxRect.left; boxDest.height = boxRect.bottom - boxRect.top; } bool spriteCollide(Entity player, Entity target) { float left1, left2; float right1, right2; float top1, top2; float bottom1, bottom2; left1 = player.X; left2 = target.X; right1 = player.X + player.length; right2 = target.X + target.length; top1 = player.Y; top2 = target.Y; bottom1 = player.Y + player.height; bottom2 = target.Y + target.height; if (bottom1 < top2) return false; if (top1 > bottom2) return false; if (right1 < left2) return false; if (left1 > right2) return false; return true; } void collideWithBox() { if ( spriteCollide(playerDest, boxDest) && keyArr[VK_UP]) //playerDest.Y += 50; playerDest.Y = boxDest.Y + boxDest.height; else if ( spriteCollide(playerDest, boxDest) && !keyArr[VK_UP]) playerDest.Y = boxDest.Y - boxDest.height; }

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• How to connect ethernet on ubuntu (with auto-detection by Ubuntu)

  - by user12285

  Do I need to post another thread for the same? If so, sorry. Yes, I saw that it's been well over six months but I have the same router SmartAX MT880d with ethernet, and the exact same problem, that is no internet even though I can successfully reach the modem settings page by entering 192.168.1.1 in Firefox. Sorry if I don't use the right (technical) terminology to express my issue. English is not my mother tongue. I'm a total beginner with ubuntu. My internet works great in Windows but does not work in Ubuntu. For 2 weeks, I've kept reading on the web and forums and the ubuntuguide.org to name a few but to no avail. Now I see no other solution but to ask for help. My problem is that as a beginner, I can't find a way to put the right digits in the right place because I don't know what numbers I need to put in what files (eg: do I need to use DHCP? or a static IP address? No clue whatsoever. I'm confused between putting figures in the wrong spaces. For example, is the modem/router's IP exactly 192.168.1.1 for Huawei Smart AXMT880d modem?? Is the subnet 255.255.255.0? Gateway 192.168.1.1. I'm confused as I can also see a different IP starting with 155131*** (is it an account number? no clue again) on my contract with Huawei (a Chinese ISP). Apart from calling 911, what other numbers do I need to put in and where? How do I check that all the numbers have been entered correctly in every appropriate space before trying to connect the Internet?

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• touch detection of non-rectangular sprites (cocos2d)

  - by hogni89

  What is the correct way to implement a non-rectangular sprite in Cocos2d? I am working on a jigsaw puzzle. And therefor do our sprites have some strange forms (Jigsaw puzzle bricks). As of now, we have implemented the "detect" this way: - (void)selectSpriteForTouch:(CGPoint)touchLocation { CCSprite * newSprite = nil; // Loop array of sprites for (CCSprite *sprite in movableSprites) { // Check if sprite is hit. // TODO: Swap if with something better. if (CGRectContainsPoint(sprite.boundingBox, touchLocation)) { newSprite = sprite; break; } } if (newSprite != selSprite) { // Move along, nothing to see here // Not the problem } } - (BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event { CGPoint touchLocation = [self convertTouchToNodeSpace:touch]; [self selectSpriteForTouch:touchLocation]; return TRUE; } I know that the problem is in the keyword "sprite.boundingBox". Is there a better way of implementing this, OR is it a limit when using sprites based on .png's? If so, how should I proceed? I'm new to iPhone and game development :D

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• Website (X)HTML Code Change Detection [closed]

  - by 0pt1m1z3

  I am looking for an enterprise-grade service or a tool that can be used to scan / fingerprint websites and notify when major XHTML code changes are detected. The tool should be able to continuously scan thousands of websites and determine the percentage of HTML code that has been modified since the last run. And then either save the data where it can be easily accessed or send periodic notifications. I know of services like ChangeDetect.com, but they don't do markup only changes and instead focus on everything, including content. We don't really care about presentation content, because a lot of sites we need to cover are updated frequently with content.

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• 3G dongle and memory card detection

  - by user212632

  My questions is about 3G dongle (Huawei E1752) that I use for my internet on Ubuntu 12.04. The big issue is that ubuntu only recognise the dongle if I plug it in before booting up. But if somehow I loses connection (due to network being low) then the only way to use the 3G dongle again is to reboot my machine, which becomes a pain. I have the same issue with the memory card reader of my laptop whereby it only reads when I insert the card before booting up. My laptop is an Acer V3 -571g. At first I thought it was an issue that the model was quite new, but I have been updating my ubuntu for a while, and this issue has kept being the same

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• Enemy collision detection with movie clips

  - by user18080

  I have created multiple movieclips with animations within them. It is an obstacle avoidance game and I cannot seem to be able to get my enemies to contact my playableCharacter. The enemies I have created are each embedded on certain levels of my game. I have created an array, enemiesArray to have each of my enemies placed within it. Here is the code for that: //step 1: make sure array exists if(enemiesArray!=null && enemiesArray.length!=0) { //step 2: check all enemies against villain for(var i:int = 0;i < enemiesArray.length; i++) { //step 3: check for collision if(villain.hitTestObject(enemiesArray[i])) { //step 4: do stuff trace("HIT!"); removeChild(enemiesArray[i]); enemiesArray.splice(i,1); removeChild(villain); villain = null; } } } What I am unsure of is whether or not my enemiesArray is actually holding the movieclips I have suggested. If it was, this code would be tracing back a "HIT" for every time I ran into an enemy and would kill my character. It is not doing that however. I am thinking I have to push my movieclips into my array but I don't know how to do that or where for that matter. Any and all help would be much appreciated.

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• Would md5 hashes allow detection of synced files?

  - by codpursue

  We have to develop our own file management system in Java web application. We need to sync files between our main server and client severs and find out whether all the client server has all the latest version of files. Our files are in pdf, doc and xls format they changes every now and then as and when it is required. What we are thinking of using MD5 checksum to find out hashcode of files on Main server and store it in database. Same would be there in Client Servers database. After comparing records on database we would come to know whether client servers are synced or not. Please suggest if there are any better ways to do the same.

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• Points on lines where the two lines are the closest together

  - by James Bedford

  Hey guys, I'm trying to find the points on two lines where the two lines are the closest. I've implemented the following method (Points and Vectors are as you'd expect, and a Line consists of a Point on the line and a non-normalized direction Vector from that point): void CDClosestPointsOnTwoLines(Line line1, Line line2, Point* closestPoints) { closestPoints[0] = line1.pointOnLine; closestPoints[1] = line2.pointOnLine; Vector d1 = line1.direction; Vector d2 = line2.direction; float a = d1.dot(d1); float b = d1.dot(d2); float e = d2.dot(d2); float d = a*e - b*b; if (d != 0) // If the two lines are not parallel. { Vector r = Vector(line1.pointOnLine) - Vector(line2.pointOnLine); float c = d1.dot(r); float f = d2.dot(r); float s = (b*f - c*e) / d; float t = (a*f - b*c) / d; closestPoints[0] = line1.positionOnLine(s); closestPoints[1] = line2.positionOnLine(t); } else { printf("Lines were parallel.\n"); } } I'm using OpenGL to draw three lines that move around the world, the third of which should be the line that most closely connects the other two lines, the two end points of which are calculated using this function. The problem is that the first point of closestPoints after this function is called will lie on line1, but the second point won't lie on line2, let alone at the closest point on line2! I've checked over the function many times but I can't see where the mistake in my implementation is. I've checked my dot product function, scalar multiplication, subtraction, positionOnLine() etc. etc. So my assumption is that the problem is within this method implementation. If it helps to find the answer, this is function supposed to be an implementation of section 5.1.8 from 'Real-Time Collision Detection' by Christer Ericson. Many thanks for any help!

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• Why doesn't Unity's OnCollisionEnter give me surface normals, and what's the most reliable way to get them?

  - by michael.bartnett

  Unity's on collision event gives you a Collision object that gives you some information about the collision that happened (including a list of ContactPoints with hit normals). But what you don't get is surface normals for the collider that you hit. Here's a screenshot to illustrate. The red line is from ContactPoint.normal and the blue line is from RaycastHit.normal. Is this an instance of Unity hiding information to provide a simplified API? Or do standard 3D realtime collision detection techniques just not collect this information? And for the second part of the question, what's a surefire and relatively efficient way to get a surface normal for a collision? I know that raycasting gives you surface normals, but it seems I need to do several raycasts to accomplish this for all scenarios (maybe a contact point/normal combination misses the collider on the first cast, or maybe you need to do some average of all the contact points' normals to get the best result). My current method: Back up the Collision.contacts[0].point along its hit normal Raycast down the negated hit normal for float.MaxValue, on Collision.collider If that fails, repeat steps 1 and 2 with the non-negated normal If that fails, try steps 1 to 3 with Collision.contacts[1] Repeat 4 until successful or until all contact points exhausted. Give up, return Vector3.zero. This seems to catch everything, but all those raycasts make me queasy, and I'm not sure how to test that this works for enough cases. Is there a better way?

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• How can I move along an angled collision at a constant speed?

  - by Raven Dreamer

  I have, for all intents and purposes, a Triangle class that objects in my scene can collide with (In actuality, the right side of a parallelogram). My collision detection and resolution code works fine for the purposes of preventing a gameobject from entering into the space of the Triangle, instead directing the movement along the edge. The trouble is, the maximum speed along the x and y axis is not equivalent in my game, and moving along the Y axis (up or down) should take twice as long as an equivalent distance along the X axis (left or right). Unfortunately, these speeds apply to the collision resolution too, and movement along the blue path above progresses twice as fast. What can I do in my collision resolution to make sure that the speedlimit for Y axis movement is obeyed in the latter case? Collision Resolution for this case below (vecInput and velocity are the position and velocity vectors of the game object): // y = mx+c lowY = 2*vecInput.x + parag.rightYIntercept ; ... else { // y = mx+c // vecInput.y = 2(x) + RightYIntercept // (vecInput.y - RightYIntercept) / 2 = x; //if velocity.Y (positive) greater than velocity.X (negative) //pushing from bottom, so push right. if(velocity.y > -1*velocity.x) { vecInput = new Vector2((vecInput.y - parag.rightYIntercept)/2, vecInput.y); Debug.Log("adjusted rightwards"); } else { vecInput = new Vector2( vecInput.x, lowY); Debug.Log("adjusted downwards"); } }

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• Need help understanding XNA 4.0 BoundingBox vs BoundingSphere Intersection

  - by nerdherd

  I am new to both game programming and XNA, so I apologize if I'm missing a simple concept or something. I have created a simple 3D game with a player and a crate and I'm working on getting my collision detection working properly. Right now I am using a BoundingSphere for my player, and a BoundingBox for the crate. For some reason, XNA only detects a collision when my player's sphere touches the front face of the crate. I'm rendering all the BoundingSpheres and BoundingBoxes as wire frames so I can see what's going on, and everything visually appears to be correct, but I can't figure out this behavior. I have tried these checks: playerSphere.Intersects(crate.getBoundingBox()) playerSphere.Contains(crate.getBoundingBox(), ContainmentType.Intersects) playerSphere.Contains(crate.getBoundingBox()) != ContainmentType.Disjoint But they all seem to produce the same behavior (in other words, they are only true when I hit the front face of the crate). The interesting thing is that when I use a BoundingSphere for my crate the collision is detected as I would expect, but of course this makes the edges less accurate. Any thoughts or ideas? Have I missed something about how BoundingSpheres and BoundingBoxes compute their intersections? I'd be happy to post more code or screenshots to clarify if needed. Thanks!

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• How can I resolve collisions at different speeds, depending on the direction?

  - by Raven Dreamer

  I have, for all intents and purposes, a Triangle class that objects in my scene can collide with (In actuality, the right side of a parallelogram). My collision detection and resolution code works fine for the purposes of preventing a gameobject from entering into the space of the Triangle, instead directing the movement along the edge. The trouble is, the maximum speed along the x and y axis is not equivalent in my game, and moving along the Y axis (up or down) should take twice as long as an equivalent distance along the X axis (left or right). Unfortunately, these speeds apply to the collision resolution too, and movement along the blue path above progresses twice as fast. What can I do in my collision resolution to make sure that the speedlimit for Y axis movement is obeyed in the latter case? Collision Resolution for this case below (vecInput and velocity are the position and velocity vectors of the game object): // y = mx+c // solve for y. M = 2, x = input's x coord, c = rightYIntercept lowY = 2*vecInput.x + parag.rightYIntercept ; ... else { // y = mx+c // vecInput.y = 2(x) + RightYIntercept // (vecInput.y - RightYIntercept) / 2 = x; //if velocity.Y (positive) greater than velocity.X (negative) //pushing from bottom, so push right. if(velocity.y > -1*velocity.x) { //change the input vector's x position to match the //y position on the shape's edge. Formula for line: Y = MX+C // M is 2, C is rightYIntercept, y is the input y, solve for X. vecInput = new Vector2((vecInput.y - parag.rightYIntercept)/2, vecInput.y); Debug.Log("adjusted rightwards"); } else { vecInput = new Vector2( vecInput.x, lowY); Debug.Log("adjusted downwards"); } }

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• Detecting Browser Types?

  - by Mike Schinkel

  My client has asked me to implement a browser detection system for the admin login with the following criteria, allow these: Internet Explorer 8 or newer Firefox 3.6 or newer Safari 5 or newer for Mac only And everything else should be blocked. They want me to implement a page telling the user what browser they need to upgrade/switch to in order to access the CMS. Basically I need to know the best way to detect these browsers with PHP, distinct from any other browsers, and I've read that browser sniffing per se is not a good idea. The CMS is WordPress but this is not a WordPress question (FYI I am a moderator on the WordPress Answers site.) Once I figure out the right technique to detect the browser I'm fully capable to make WordPress react as my client wants, I just need to know what the best ways are with PHP (or worse case jQuery, but I much prefer to do on the server) to figure how what works and what doesn't. Please understand that "Don't do it" is not an acceptable answer for this question. I know this client too well and when they ask me to implement something I need to do it (they are a really good client so I'm happy to do what they ask.) Thanks in advance for your expertise. -Mike

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• Change collision action

  - by PatrickR

  I have a collision detection and its working fine, the problem is, that whenever my "bird" is hitting a "cloud", the cloud dissapers and i get some points. The same happens for the "sol" which it should, but not with the clouds. How can this be changed ? ive tryed a lot, but can seem to figger it out. Collision Code - (void)update:(ccTime)dt { bird.position = ccpAdd(bird.position, skyVelocity); NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; for (CCSprite *bird in _projectiles) { bird.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(bird.position.x, bird.position.y, [bird boundingBox].size.width, [bird boundingBox].size.height); NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *cloudSprite in _targets) { cloudSprite.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(cloudSprite.position.x, cloudSprite.position.y, [cloudSprite boundingBox].size.width, [cloudSprite boundingBox].size.height); if (CGRectIntersectsRect([bird boundingBox], [cloudSprite boundingBox])) { [targetsToDelete addObject:cloudSprite]; } } for (CCSprite *solSprite in _targets) { solSprite.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(solSprite.position.x, solSprite.position.y, [solSprite boundingBox].size.width, [solSprite boundingBox].size.height); if (CGRectIntersectsRect([bird boundingBox], [solSprite boundingBox])) { [targetsToDelete addObject:solSprite]; score += 50/2; [scoreLabel setString:[NSString stringWithFormat:@"%d", score]]; } } // NÅR SKYEN BLIVER RAMT AF FUGLEN for (CCSprite *cloudSprite in targetsToDelete) { //[_targets removeObject:cloudSprite]; //[self removeChild:cloudSprite cleanup:YES]; } // NÅR SOLEN BLIVER RAMT AF FUGLEN for (CCSprite *solSprite in targetsToDelete) { [_targets removeObject:solSprite]; [self removeChild:solSprite cleanup:YES]; } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:bird]; } [targetsToDelete release]; } // NÅR FUGLEN BLIVER RAMT AF ALT ANDET for (CCSprite *bird in projectilesToDelete) { //[_projectiles removeObject:bird]; //[self removeChild:bird cleanup:YES]; } [projectilesToDelete release]; }

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• LWJGL Java 2D collision when lagging

  - by user1990950

  I'm using a tile based collision, but when the game is lagging (the lag isn't the problem) the collision fails and the player falls through tiles. This is the movement/collision detection code of my Player class: gravity.y = gspeed; speed.y+=gravity.y; position.set(position.x + direction.x * speed.x * deltaSeconds, position.y + direction.y * speed.y * deltaSeconds); for (int i = (int) Math.round(position.x / 32) - 2 * t; i < (int) Math.round(position.x / 32) + 3 * t; i++) { for (int j = (int) Math.round(position.y / 32); j < (int) Math.round((position.y + height + 64) / 32); j++) { checkCollision(i, j, deltaSeconds); } } public void checkCollision(int i, int j, float deltaSeconds) { bbox.setBounds((int) position.x, (int) position.y, (int) width, (int) height); Tile t = null; t = Map.getTile(i, j); if (t != null) { if (t.isSolid()) { if (t.getTop().intersects(bbox)) { if (position.y + height < t.y * 32 + 32) { if (speed.y >= 0) { position.y = t.y * 32 - height; speed.y = 0; gravity.y = 0; jumpState = 0; } } } if (t.getBottom().intersects(bbox)) { if (position.y < t.y * 32 + 32) { position.y = t.y * 32 + 32; speed.y = 0; } } else { if (t.getLeft().intersects(bbox)) { if (position.x + width > t.x * 32) { position.x = t.x * 32 - width; speed.x = 0; } } if (t.getRight().intersects(bbox)) { if (position.x < t.x * 32 + 32) { position.x = t.x * 32 + 32; speed.x = 0; } } } } } } Is it possible to fix my code, if yes how? Or is it possible to tell if the game is lagging?

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• What kind of physics to choose for our arcade 3D MMO?

  - by Nick

  We're creating an action MMO using Three.js (WebGL) with an arcadish feel, and implementing physics for it has been a pain in the butt. Our game has a terrain where the character will walk on, and in the future 3D objects (a house, a tree, etc) that will have collisions. In terms of complexity, the physics engine should be like World of Warcraft. We don't need friction, bouncing behaviour or anything more complex like joints, etc. Just gravity. I have managed to implement terrain physics so far by casting a ray downwards, but it does not take into account possible 3D objects. Note that these 3D objects need to have convex collisions, so our artists create a 3D house and the player can walk inside but can't walk through the walls. How do I implement proper collision detection with 3D objects like in World of Warcraft? Do I need an advanced physics engine? I read about Physijs which looks cool, but I fear that it may be overkill to implement that for our game. Also, how does WoW do it? Do they have a separate raycasting system for the terrain? Or do they treat the terrain like any other convex mesh? A screenshot of our game so far:

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• Detecting walls or floors in pygame

  - by Serial

  I am trying to make bullets bounce of walls, but I can't figure out how to correctly do the collision detection. What I am currently doing is iterating through all the solid blocks and if the bullet hits the bottom, top or sides, its vector is adjusted accordingly. However, sometimes when I shoot, the bullet doesn't bounce, I think it's when I shoot at a border between two blocks. Here is the update method for my Bullet class: def update(self, dt): if self.can_bounce: #if the bullet hasnt bounced find its vector using the mousclick pos and player pos speed = -10. range = 200 distance = [self.mouse_x - self.player[0], self.mouse_y - self.player[1]] norm = math.sqrt(distance[0] ** 2 + distance[1] ** 2) direction = [distance[0] / norm, distance[1 ] / norm] bullet_vector = [direction[0] * speed, direction[1] * speed] self.dx = bullet_vector[0] self.dy = bullet_vector[1] #check each block for collision for block in self.game.solid_blocks: last = self.rect.copy() if self.rect.colliderect(block): topcheck = self.rect.top < block.rect.bottom and self.rect.top > block.rect.top bottomcheck = self.rect.bottom > block.rect.top and self.rect.bottom < block.rect.bottom rightcheck = self.rect.right > block.rect.left and self.rect.right < block.rect.right leftcheck = self.rect.left < block.rect.right and self.rect.left > block.rect.left each test tests if it hit the top bottom left or right side of the block its colliding with if self.can_bounce: if topcheck: self.rect = last self.dy *= -1 self.can_bounce = False print "top" if bottomcheck: self.rect = last self.dy *= -1 #Bottom check self.can_bounce = False print "bottom" if rightcheck: self.rect = last self.dx *= -1 #right check self.can_bounce = False print "right" if leftcheck: self.rect = last self.dx *= -1 #left check self.can_bounce = False print "left" else: # if it has already bounced and colliding again kill it self.kill() for enemy in self.game.enemies_list: if self.rect.colliderect(enemy): self.kill() #update position self.rect.x -= self.dx self.rect.y -= self.dy This definitely isn't the best way to do it but I can't think of another way. If anyone has done this or can help that would be awesome!

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• How to make it so units don't stack up in one location?

  - by Daggio

  So I'm making a game in AS3, it's a strategy DotA-like game (for flash game equivalent, there's UDE) so far so good, I have the A* pathfinding algorithm all sorted out and the minion units move to the desired location as I want them to be. The problem a rise when a unit stops in a node that has already occupied by another friendly unit. Both (or more than two) of them stacks up in one location, it looks like they're one unit. I want to add collision detection so when they collide they don't stack up together. But now they stop when they collide on they way to a node. This isn't good because they won't move at all midway (they won't respond to enemy attacks like that). I've added a deltatime so they only stopped for 2 seconds before they move again to their designated designation. This moves them again but they flicker. Not how I want it. So, like the title said. How to make more than one units don't stack up in a node? And if possible, how to make them not flicker while moving (it's good if they can tell other friendly units on the way and avoid them accordingly)?

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