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• Bukkit inventory saving: crashing somewhere

  - by HcgRandon

  I'm working on a command for a bukkit plugin that lets you transfer worlds. In the section about saving the player's inventory, I'm getting a runtime error. My question is: Why is the error happening, and how can I prevent it? The plugin code public void savePlayerInv(Player p, World w){ File playerInvConfigFile = new File(plugin.getDataFolder() + File.separator + "players" + File.separator + p.getName(), "inventory.yml"); FileConfiguration pInv = YamlConfiguration.loadConfiguration(playerInvConfigFile); PlayerInventory inv = p.getInventory(); int i = 0; for (ItemStack stack : inv.getContents()) { //increment integer i++; String startInventory = w.getName() + ".inv." + Integer.toString(i); //save inv pInv.set(startInventory + ".amount", stack.getAmount()); pInv.set(startInventory + ".durability", Short.toString(stack.getDurability())); pInv.set(startInventory + ".type", stack.getTypeId()); //pInv.set(startInventory + ".enchantment", stack.getEnchantments()); //TODO add enchant saveing } i = 0; for (ItemStack armor : inv.getArmorContents()){ i++; String startArmor = w.getName() + ".armor." + Integer.toString(i); //save armor pInv.set(startArmor + ".amount", armor.getAmount()); pInv.set(startArmor + ".durability", armor.getDurability()); pInv.set(startArmor + ".type", armor.getTypeId()); //pInv.set(startArmor + ".enchantment", armor.getEnchantments()); } //save exp if (p.getExp() != 0) { pInv.set(w.getName() + ".exp", p.getExp()); } } The offending line The stack trace complains about line 130, which is this line. pInv.set(startInventory + ".amount", stack.getAmount()); The stack trace 2012-03-21 13:23:25 [SEVERE] null org.bukkit.command.CommandException: Unhandled exception executing command 'wtp' in plugin Needs v1.0 at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42) at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:166) at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:461) at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:818) at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:778) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:761) at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33) at net.minecraft.server.NetworkManager.b(NetworkManager.java:229) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:112) at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78) at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:554) at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:452) at net.minecraft.server.ThreadServerApplication.run(SourceFile:490) Caused by: java.lang.NullPointerException at com.devoverflow.improved.needs.commands.CommandWorldtp.savePlayerInv(CommandWorldtp.java:130) at com.devoverflow.improved.needs.commands.CommandWorldtp.onCommand(CommandWorldtp.java:60) at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40) ... 12 more

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• I need help with specific types of movement.

  - by IronGiraffe

  I'm adding movable crates to my game and I need some help with my movement code. The way I've set up my movement code the crate's X and Y are moved according to a vector2 unless it hits a wall. Here's the movement code: if (frameCount % (delay / 2) == 0) { for (int i = 0; i < Math.Abs(cSpeed.X); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X += Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } else { if (!Level.CollideTiles(crateBounds.X - (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X -= Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } } for (int i = 0; i < Math.Abs(cSpeed.Y); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y += Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } else { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y - Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y -= Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } } } The frameCount and delay variables just slow down the movement somewhat. Anyway, I've added a tool to my game that acts as a gravity well (drawing objects into it's center; the closer they get to the center the faster they go) and what I'm trying to do is make it so that the crate will bounce off the player (and vice versa) when they collide. Thus far, my code only keeps the crate and player from getting stuck inside each other (the player can still get stuck under the crate, but I'll fix that later.) So what I'd like to know is how I can best make the crate bounce off the player. The other movement problem I'm having is related to another tool which allows the player to pick up crates and move around with them. The problem is that the crate's movement while being carried isn't tied to the movement script (it moves the crate itself, instead of adding to speed), which makes the crate go through walls and such. I know what I have to do: make the crate's speed match the player's speed while the player is holding it, but I need the crate to snap to a certain position (just in front of the player) when the player grabs it and it needs to switch to another position (just in front of the player on the other side) when they player faces the other direction while holding it. What would be the best way to make it switch places while keeping all the movement tied to the speed vector?

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• Making a clone of Starcraft legal?

  - by user782220

  My question is similar to a previous question. Consider the following clone of Starcraft: Change the artwork, sound, music, change the names of units. However, leave the unit hit points unchanged, unit damage unchanged, unit movement speed unchanged, change ability names but not ability effects. Is that considered illegal? In other words, is copying the unit hit points, damage, etc. considered illegal even if everything else is changed?

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• One-way platform collision

  - by TheBroodian

  I hate asking questions that are specific to my own code like this, but I've run into a pesky roadblock and could use some help getting around it. I'm coding floating platforms into my game that will allow a player to jump onto them from underneath, but then will not allow players to fall through them once they are on top, which require some custom collision detection code. The code I have written so far isn't working, the character passes through it on the way up, and on the way down, stops for a moment on the platform, and then falls right through it. Here is the code to handle collisions with floating platforms: protected void HandleFloatingPlatforms(Vector2 moveAmount) { //if character is traveling downward. if (moveAmount.Y > 0) { Rectangle afterMoveRect = collisionRectangle; afterMoveRect.Offset((int)moveAmount.X, (int)moveAmount.Y); foreach (World_Objects.GameObject platform in gameplayScreen.Entities) { if (platform is World_Objects.Inanimate_Objects.FloatingPlatform) { //wideProximityArea is just a rectangle surrounding the collision //box of an entity to check for nearby entities. if (wideProximityArea.Intersects(platform.CollisionRectangle) || wideProximityArea.Contains(platform.CollisionRectangle)) { if (afterMoveRect.Intersects(platform.CollisionRectangle)) { //This, in my mind would denote that after the character is moved, its feet have fallen below the top of the platform, but before he had moved its feet were above it... if (collisionRectangle.Bottom <= platform.CollisionRectangle.Top) { if (afterMoveRect.Bottom > platform.CollisionRectangle.Top) { //And then after detecting that he has fallen through the platform, reposition him on top of it... worldLocation.Y = platform.CollisionRectangle.Y - frameHeight; hasCollidedVertically = true; } } } } } } } } In case you are curious, the parameter moveAmount is found through this code: elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; float totalX = 0; float totalY = 0; foreach (Vector2 vector in velocities) { totalX += vector.X; totalY += vector.Y; } velocities.Clear(); velocity.X = totalX; velocity.Y = totalY; velocity.Y = Math.Min(velocity.Y, 1000); Vector2 moveAmount = velocity * elapsed;

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• Box2dWeb positioning relative to HTML5 Canvas

  - by Joe

  I'm new with HTML5 canvas and Box2DWeb and I'm trying to make an Asteroids game. So far I think I'm doing okay, but one thing I'm struggling to comprehend is how positioning works in relation to the canvas. I understand that Box2DWeb is only made to deal with physical simulation, but I don't know how to deal with positioning on the canvas. The canvas is 100% viewport and thus can vary size. I want to fill the screen with some asteroids, but if I hardcore certain values such as bodyDef.position.x = Math.random() * 50; the asteroid may appear off canvas for someone with a smaller screen? Can anybody help me understand how I can deal with relative positioning on the canvas?

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• How to sync client and server at the first frame

  - by wheelinlight

  I'm making a game where an authoritative server sends information to all clients about states and positions for objects in a 3d world. The player can control his character by clicking on the screen to set a destination for the character, much like in the Diablo series. I've read most information I can find online about interpolation, reconciliation, and general networking architecture (Valve's for instance). I think I understand everything but one thing seems to be missing in every article I read. Let say we have an interpolation delay of 100ms, server tickrate=50ms, latency=200ms; How do I know when 100ms has past on the client? If the server sends the first update on t=0, can I assume it arrives at t=200, therefore assuming that all packets takes the same amount of time to reach the client? What if the first packet arrives a little quick, for instance at t=150. I would then be starting the client with t=150 and at t=250 it will think it has past 100ms since its connect to the server when it in fact only 50ms has past. Hopefully the above paragraph is understandable. The summarized question would be: How do I know at what tick to start simulating the client? EDIT: This is how I ended up doing it: The client keeps a clock (approximately) in sync with the server. The client then simulates the world at simulationTime = syncedTime - avg(RTT)/2 - interpolationTime The round-trip time can fluctuate so therefore I average it out over time. By only keeping the most recent values when calculating the average I hope to adapt to more permanent changes in latency. It's still to early to draw any conclusion. I'm currently simulating bad network connections, but it's looking good so far. Anyone see any possible problems?

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• Need a good quality bitmap rotation algorithm for Android

  - by Lumis

  I am creating a kaleidoscopic effect on an android tablet. I am using the code below to rotate a slice of an image, but as you can see in the image when rotating a bitmap 60 degrees it distorts it quite a lot (red rectangles) – it is smudging the image! I have set dither and anti-alias flags but it does not help much. I think it is just not a very sophisticated bitmap rotation algorithm. canvas.save(); canvas.rotate(angle, screenW/2, screenH/2); canvas.drawBitmap(picSlice, screenW/2, screenH/2, pOutput); canvas.restore(); So I wonder if you can help me find a better way to rotate a bitmap. It does not have to be fast, because I intend to use a high quality rotation only when I want to save the screen to the SD card - I would redraw the screen in memory before saving. Do you know any comprehensible or replicable algorithm for bitmap rotation that I could programme or use as a library? Or any other suggestion? EDIT: The answers below made me think if Android OS had bilinear or bicubic interpolation option and after some search I found that it does have its own version of it called FilterBitmap. After applying it to my paint pOutput.setFilterBitmap(true); I get much better result

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• Rotating 2D Object

  - by Vico Pelaez

  Well I am trying to learn openGL and want to make a triangle move one unit (0.1) everytime I press one of the keyboard arrows. However i want the triangle to turn first pointing the direction where i will move one unit. So if my triangle is pointing up and I press right the it should point right first and then move one unit in the x axis. I have implemented the code to move the object one unit in any direction, however I can not get it to turn pointing to the direction it is going. The initial position of the Triangle is pointing up. #define LENGTH 0.05 float posX = -0.5, posY = -0.5, posZ = 0; float inX = 0.0 ,inY = 0.0 ,inZ = 0.0; // what values???? void rect(){ glMatrixMode(GL_PROJECTION); glLoadIdentity(); glPushMatrix(); glTranslatef(posX,posY,posZ); glRotatef(rotate, inX, inY, inZ); glBegin(GL_TRIANGLES); glColor3f(0.0, 0.0, 1.0); glVertex2f(-LENGTH,-LENGTH); glVertex2f(LENGTH-LENGTH, LENGTH); glVertex2f(LENGTH, -LENGTH); glEnd(); glPopMatrix(); } void display(){ //Clear Window glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); rect(); glFlush(); } void init(){ glClearColor(0.0, 0.0, 0.0, 0.0); glColor3f(1.0, 1.0, 1.0); } float move_unit = 0.01; bool change = false; void keyboardown(int key, int x, int y) { switch (key){ case GLUT_KEY_UP: if(rotate = 0) posY += move_unit; else{ inX = 1.0; rotate = 0; } break; case GLUT_KEY_RIGHT: if(rotate = -90) posX += move_unit; else{ inX = 1.0; // is this value ok?? rotate -= 90; } break; case GLUT_KEY_LEFT: if(rotate = 90) posX -= move_unit; else{ inX = 1.0; // is this value ok??? rotate += 90; } break; case GLUT_KEY_DOWN: if(rotate = 180) posY -= move_unit; else{ inX = 1.0; rotate += 180; } break; case 27: // Escape button exit(0); break; default: break; } glutPostRedisplay(); } int main(int argc, char** argv){ glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(500,500); glutInitWindowPosition(0, 0); glutCreateWindow("Triangle turn"); glutSpecialFunc(keyboardown); glutDisplayFunc(display); init(); glutMainLoop()

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• Extremely simple online multiplayer game

  - by Postscripter

  I am considering creating a simple multiplayer game, which focuses on physics and can accommodate up to 30 players per session. Very simple graphics, but smart physics (pushing, weight and gravity, balance) is required. After some research I found a good java script (framework ??) called box2d.js I found the demo to be excellent. this is is kind of physics am looking for in my game. Now, what other frameworks will I need? Node.js?? Prototype.js?? (btw, I found the latest versoin of protoype.js to be released in 2010...?? is this still supported? Should I avoid using it?) What bout HTML 5 and Canvas? would I need them? websockets? Am a beginner in web programming + game programming world. but I will learn fast, am computer science graduate. (but no much web expeience but know essentionals javascript, html, css..). I just need a guiding path to build my game. Thanks

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• Costs/profit of/when starting an indie company

  - by Jack

  In short, I want to start a game company. I do not have much coding experience (just basic understanding and ability to write basic programs), any graphics design experience, any audio mixing experience, or whatever else technical. However, I do have a lot of ideas, great analytical skills and a very logical approach to life. I do not have any friends who are even remotely technical (or creative in regards to games for that matter). So now that we've cleared that up, my question is this: how much, minimally, would it cost me to start such a company? I know that a game could be developed in under half a year, which means it would have to operate for half a year prior, and that's assuming that the people working on the first project do their jobs good, don't leave game breaking bugs, a bunch of minor bugs, etc.. So how much would it cost me, and what would be the likely profit in half a year? I'm looking at minimal costs here, as to do it, I would have to sell my current apartment and buy a new, smaller one, pay taxes, and likely move to US/CA/UK to be closer to technologically advanced people (and be able to speak the language of course). EDIT: I'm looking at a small project for starters, not a huge AAA title.

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• Objects disappear when zoomed out in Unity

  - by Starkers

  Ignore the palm trees here. I have some oak-like trees when I'm zoomed in: They disappear when I zoom out: Is this normal? Is this something to do with draw distance? How can I change this so my trees don't disappear? The reason I ask is because my installation had a weird terrain glitch. If this isn't normal I'm going to reinstall right away because I'm always thinking 'is that a feature? Or a glitch'?

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• Box2D Difference Between WorldCenter and Position

  - by Free Lancer

  So this problem has been brothering for a couple of days now. First off, what is the difference between say Body.getWorldCenter() and Body.getPosition(). I heard that WorldCenter might have to do with the center of gravity or something. Second, When I create a Box2D Body for a sprite the Body is always at the lower left corner. I check it by printing a Rectangle of 1 pixel around the box.getWorldCenter(). From what I understand the Body should be in the center of the Sprite and its bounding box should wrap around the Sprite, correct? Here's an image of what I mean (The Sprite is Red, Body Blue): Here's some code: Body Creator: public static Body createBoxBody( final World pPhysicsWorld, final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pCenterX = pSprite.getX() + pSprite.getWidth() / 2; float pCenterY = pSprite.getY() + pSprite.getHeight() / 2; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; //boxBodyDef.position.x = pCenterX / Constants.PIXEL_METER_RATIO; //boxBodyDef.position.y = pCenterY / Constants.PIXEL_METER_RATIO; boxBodyDef.position.x = pSprite.getX() / Constants.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Constants.PIXEL_METER_RATIO; Vector2 v = new Vector2( boxBodyDef.position.x * Constants.PIXEL_METER_RATIO, boxBodyDef.position.y * Constants.PIXEL_METER_RATIO ); Gdx.app.log("@Physics", "createBoxBody():: Box Position: " + v); // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Constants.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Constants.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = pPhysicsWorld.createBody(boxBodyDef); Gdx.app.log("@Physics", "createBoxBody():: Box Center: " + boxBody.getPosition().mul(Constants.PIXEL_METER_RATIO)); boxBody.createFixture(pFixtureDef); boxBody.setTransform( boxBody.getWorldCenter(), MathUtils.degreesToRadians * pRotation ); boxPoly.dispose(); return boxBody; } Making the Sprite: public Car( Texture texture, float pX, float pY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( mSprite.getWidth() / 6, mSprite.getHeight() / 6 ); mSprite.setPosition( pX, pY ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); FixtureDef carFixtureDef = new FixtureDef(); // Set the Fixture's properties, like friction, using the car's shape carFixtureDef.restitution = 1f; carFixtureDef.friction = 1f; carFixtureDef.density = 1f; // needed to rotate body using applyTorque mBody = Physics.createBoxBody( world, BodyDef.BodyType.DynamicBody, carFixtureDef, mSprite ); }

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• Bounding Box Collision Glitching Problem (Pygame)

  - by Ericson Willians

  So far the "Bounding Box" method is the only one that I know. It's efficient enough to deal with simple games. Nevertheless, the game I'm developing is not that simple anymore and for that reason, I've made a simplified example of the problem. (It's worth noticing that I don't have rotating sprites on my game or anything like that. After showing the code, I'll explain better). Here's the whole code: from pygame import * DONE = False screen = display.set_mode((1024,768)) class Thing(): def __init__(self,x,y,w,h,s,c): self.x = x self.y = y self.w = w self.h = h self.s = s self.sur = Surface((64,48)) draw.rect(self.sur,c,(self.x,self.y,w,h),1) self.sur.fill(c) def draw(self): screen.blit(self.sur,(self.x,self.y)) def move(self,x): if key.get_pressed()[K_w] or key.get_pressed()[K_UP]: if x == 1: self.y -= self.s else: self.y += self.s if key.get_pressed()[K_s] or key.get_pressed()[K_DOWN]: if x == 1: self.y += self.s else: self.y -= self.s if key.get_pressed()[K_a] or key.get_pressed()[K_LEFT]: if x == 1: self.x -= self.s else: self.x += self.s if key.get_pressed()[K_d] or key.get_pressed()[K_RIGHT]: if x == 1: self.x += self.s else: self.x -= self.s def warp(self): if self.y < -48: self.y = 768 if self.y > 768 + 48: self.y = 0 if self.x < -64: self.x = 1024 + 64 if self.x > 1024 + 64: self.x = -64 r1 = Thing(0,0,64,48,1,(0,255,0)) r2 = Thing(6*64,6*48,64,48,1,(255,0,0)) while not DONE: screen.fill((0,0,0)) r2.draw() r1.draw() # If not intersecting, then moves, else, it moves in the opposite direction. if not ((((r1.x + r1.w) > (r2.x - r1.s)) and (r1.x < ((r2.x + r2.w) + r1.s))) and (((r1.y + r1.h) > (r2.y - r1.s)) and (r1.y < ((r2.y + r2.h) + r1.s)))): r1.move(1) else: r1.move(0) r1.warp() if key.get_pressed()[K_ESCAPE]: DONE = True for ev in event.get(): if ev.type == QUIT: DONE = True display.update() quit() The problem: In my actual game, the grid is fixed and each tile has 64 by 48 pixels. I know how to deal with collision perfectly if I moved by that size. Nevertheless, obviously, the player moves really fast. In the example, the collision is detected pretty well (Just as I see in many examples throughout the internet). The problem is that if I put the player to move WHEN IS NOT intersecting, then, when it touches the obstacle, it does not move anymore. Giving that problem, I began switching the directions, but then, when it touches and I press the opposite key, it "glitches through". My actual game has many walls, and the player will touch them many times, and I can't afford letting the player go through them. The code-problem illustrated: When the player goes towards the wall (Fine). When the player goes towards the wall and press the opposite direction. (It glitches through). Here is the logic I've designed before implementing it: I don't know any other method, and I really just want to have walls fixed in a grid, but move by 1 or 2 or 3 pixels (Slowly) and have perfect collision without glitching-possibilities. What do you suggest?

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• keyPressed is not working after adding ActionListener to JButton

  - by Yehonatan

  I have a serious problem while trying to build a menu for my game. I've added two JButton to a main JPanel and added an ActionListener for each of them. The main JPanel also contains the game JPanel which have the keyPressed method inside keyController. That's how it looks - Main -       JPanel -         JButton, JButton,         JPanel which contains the game and keyPressed function inside KeyController class which worked fine before I added the ActionListener for JButton. For some reason after I added an ActionListener for each of the button, the game JPanel is not getting any keyPreseed events nor KeyRealesed. Does anyone know the solution for my situation? Thank you very much! Main window - Scanner in = new Scanner(System.in); JFrame f = new JFrame("Square V.S Circles"); f.setUndecorated(true); f.setResizable(false); f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); f.add(new JPanelHandler()); f.pack(); f.setVisible(true); f.setLocationRelativeTo(null); JPanelHandler(main JPanel) - super.setFocusable(true); JButton mybutton = new JButton("Quit"); JButton sayhi = new JButton("Say hi"); sayhi.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { System.out.println("Hi"); } }); mybutton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { System.exit(0); } }); add(mybutton); add(sayhi); add(new Board(2)); Board KeyController(The code inside is working so it's unnecessary to put it here) - private class KeyController extends KeyAdapter { public KeyController() { ..Code } @Override public void keyPressed(KeyEvent e) { ...Code } @Override public void keyReleased(KeyEvent e){ ...Code } }

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• Equation / formula to determine an objects position on an ellipitcal path

  - by David Murphy

  I'm making a space game, as such I need objects to follow an elliptical path (orbit). I've worked out how to calculate all the important aspects of my orbits, the only remaining thing is how to have an object follow it. My Orbit class contains the major, minor (and by extension semi-major,semi-minor) lengths. The focii radius, area and circumference even. What is the equation to determine an objects x/y position (only need 2D) on an ellipse with a certain speed after a period of time. Basically, every frame I want to update the position based on the amount of elapsed time. I would like to have the speed along the path speed up and slow down according to the distance from the object it's orbiting, but not sure how to factor this in to the above given that at any point in time the speed has changed from it's previous speed. EDIT I can't answer my own question. But I found the question and answer is already on stackexchange: Kepler orbit : get position on the orbit over time

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• How to prevent showing outside of world game in Cocos2D-x

  - by HRZ

  I'm trying to make a tower defense game and it can zoom in/out and scrolling over my world map. How to scroll over the game and how to restrict it not to show outside of my map(black area). At below I scroll over the map by using CCCamera but I don't know how I can restrict it. CCPoint tap = touch->getLocation(); CCPoint prev_tap = touch->getPreviousLocation(); CCPoint sub_point = tap - prev_tap; float xNewPos, yNewPos; float xEyePos, yEyePos, zEyePos; float cameraPosX, cameraPosY, cameraPosZ; // First we get the current camera position. GameLayer->getCamera()->getCenterXYZ(&cameraPosX, &cameraPosY, &cameraPosZ); GameLayer->getCamera()->getEyeXYZ(&xEyePos, &yEyePos, &zEyePos); // Calculate the new position xNewPos = cameraPosX - sub_point.x; yNewPos = cameraPosY - sub_point.y; GameLayer->getCamera()->setCenterXYZ(xNewPos, yNewPos, cameraPosZ); GameLayer->getCamera()->setEyeXYZ(xNewPos, yNewPos, zEyePos); And for zooming I used such code: GameLayer->setScale(GameLayer->getScale() + 0.002); //zooming in

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• How to achieve selection of a tile from a tile sheet based on an ID?

  - by Bugster

  Let's say I have a tile sheet that contains 8 sprites per sheet. Each sprite is a tile of 30x30. I wrote my own custom map parser/map loader however I'm having trouble extracting a certain tile sprite from the file. I'll describe my problem better in order for everyone to understand. I wrote an enum of materials, each material has a value according to it's location relative to the tile sheet. For example void is 1, grass is 2, rock is 3, etc. So in my tile sheet they are represented as such: +---+---+---+---+---+ | 1 | 2 | 3 | 4 | 5 | +---+---+---+---+---+ Which is equivalent to: +------+-------+-------+ | void | grass | stone | +------+-------+-------+ Basically when rendering, I created a tile class, each tile has 2 coordinates: X and Y (They are calculated automatically) and a material which can be represented either as a number, either as a value (ID). When rendering, I have a vector of sprites which are all taken from 1 file called tilesheet.png, however each of them must only draw a certain portion of the tile sheet, for example say I have something like this: tile coordinateBounds(topLeftX, topLeftY, tileWidth, tileHeight); During the initialization of the map I calculate an array of tiles, and I give each of them their position, their materials based on the values in a map file and a few other variables such as collision. I need to apply the coordinateBounds to each of them according to their material value. For example if the material is grass it should only take the grass sprite from the tilesheet. I must also mention I'm using SFML, and there are no borders or spacing between the tiles.

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• How does this circle collision detection math work?

  - by Griffin

  I'm going through the wildbunny blog to learn about collision detection. I'm confused about how the vectors he's talking about come into play. Here's the part that confuses me: p = ||A-B|| – (r1+r2) The two spheres are penetrating by distance p. We would also like the penetration vector so that we can correct the penetration once we discover it. This is the vector that moves both circles to the point where they just touch, correcting the penetration. Importantly it is not only just a vector that does this, it is the only vector which corrects the penetration by moving the minimum amount. This is important because we only want to correct the error, not introduce more by moving too much when we correct, or too little. N = (A-B) / ||A-B|| P = N*p Here we have calculated the normalised vector N between the two centres and the penetration vector P by multiplying our unit direction by the penetration distance. I understand that p is the distance by which the circles penetrate, but I don't get what exactly N and P are. It seems to me N is just the coordinates of the 3rd point of the right trianlge formed by point A and B (A-B) then being divided by the hypotenuse of that triangle or distance between A and B (||A-B||). What's the significance of this? Also, what is the penetration vector used for? It seems to me like a movement that one of the circles would perform to get un-penetrated.

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• How should I choose quadtree depth?

  - by Evpok

  I'm using a quadtree to prune collision detection pairs in a 2d world. How should I choose to what depth said quadtree is calculated? The world is made mostly of moving objects1, so the cost of dispatching the objects between the quadtree cells matters. What is the relationship between the gain from less collision checking and the loss from more dispatching? How can I strike a balance that performs optimally? 1 To be completely explicit, they are autonomous self-replicating cells competing for food sources. This is an attempt to show my pupils predator-prey dynamics and genetic evolution at work.

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• How are larger games organized?

  - by Matthew G.

  I'm using Java, but the language I'm using here is probably irrelevant. I'd like to create an economy based on an ancient civilization. I'm not sure how to design it. If I were working on a smaller game, like a copy of "Space Invaders", I'd have no problem structuring it like this. Game -Main Control Class --Graphics Class --Player Class --Enemy class I'd pass the graphics class to both the player and enemy class so they could call graphics functions. I don't understand how I'd do this for larger projects. Do I create a country class that contains a bunch of towns? Do the towns contain a lot building class, most contain classes of people? Do I make a path finding class that the player can access to get around? How exactly do I structure this and pass all these references around? Thanks.

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• How to detect a touch on transparent area of an image in a (libgdx) stage?

  - by Usman

  Can some one please help to detect a touch on an image which I am using as an actor in a stage. The image is actually a long diagnol brush which has plenty of transparent area. The problem is when I touche the transparent area of the brush image it is also triggering the clicklistener of the image. I need the click listener should only be called when the finger actually touched the visible image not the area which is empty. I am using libgdx-0.9.4 libraries. Here is my simple piece of code. import com.badlogic.gdx.scenes.scene2d.ui.Image; import com.badlogic.gdx.scenes.scene2d.ui.ClickListener; Image brushImg = new Image(ImageCache.getTexture("brush")); brushImg.width = mStage.width()*0.75f; brushImg.height = mStage.height()*0.75f; brushImg.setClickListener(new ClickListener() { @Override public void click(Actor actor, float x, float y) { SoundFactory.play("brush"); }

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• NPOT texture and video memory usage

  - by Eonil

  I read in this QA that NPOT will take memory as much as next POT sized texture. It means it doesn't give any benefit than POT texture with proper management. (maybe even worse because NPOT should be slower!) Is this true? Does NPOT texture take and waste same memory like POT texture? I am considering NPOT texture for post-processing, so if it doesn't give memory space benefit, using of NPOT texture is meaningless to me. Maybe answer can be different for each platforms. I am targeting mobile devices. Such as iPhone or Androids. Does NPOT texture takes same amount of memory on mobile GPUs?

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• Using Instance Nodes, worth it?

  - by Twitch

  I am making a 2d game where there are various environments with lots and lots of objects. There is a forest scene with like 1200 objects in total(trees mainly), of which around 100 are visible on the camera at any given time, as you move through the level. These are comprised of around 20 different kind of trees and other props. Each object is usually 2-6 triangles with a transparent texture. My developer asked me to replace each object in the scene with a node, and keeping only a minimal amount of actual objects which would be 300+ or so(?), since there are a few modified unique meshes. So he can instantiate the actual objects to keep the game light. Is this actually effective? And if so how much? I 've read about draw calls and such and I suppose that if I combine each texture (10 kinds of trees) in 1 mesh it will have the same effect?

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• How do I drag my widgets without dragging other widgets?

  - by Cypher

  I have a bunch of drag-able widgets on screen. When I am dragging one of the widgets around, if I drag the mouse over another widget, that widget then gets "snagged" and is also dragged around. While this is kind of a neat thing and I can think of a few game ideas based on that alone, that was not intended. :-P Background Info I have a Widget class that is the basis for my user interface controls. It has a bunch of properties that define it's size, position, image information, etc. It also defines some events, OnMouseOver, OnMouseOut, OnMouseClick, etc. All of the event handler functions are virtual, so that child objects can override them and make use of their implementation without duplicating code. Widgets are not aware of each other. They cannot tell each other, "Hey, I'm dragging so bugger off!" Source Code Here's where the widget gets updated (every frame): public virtual void Update( MouseComponent mouse, KeyboardComponent keyboard ) { // update position if the widget is being dragged if ( this.IsDragging ) { this.Left -= (int)( mouse.LastPosition.X - mouse.Position.X ); this.Top -= (int)( mouse.LastPosition.Y - mouse.Position.Y ); } ... // define and throw other events if ( !this.WasMouseOver && this.IsMouseOver && mouse.IsButtonDown( MouseButton.Left ) ) { this.IsMouseDown = true; this.MouseDown( mouse, new EventArgs() ); } ... // define and throw other events } And here's the OnMouseDown event where the IsDraggable property gets set: public virtual void OnMouseDown( object sender, EventArgs args ) { if ( this.IsDraggable ) { this.IsDragging = true; } } Problem Looking at the source code, it's obvious why this is happening. The OnMouseDown event gets fired whenever the mouse is hovered over the Widget and when the left mouse button is "down" (but not necessarily in that order!). That means that even if I hold the mouse down somewhere else on screen, and simply move it over anything that IsDraggable, it will "hook" onto the mouse and go for a ride. So, now that it's obvious that I'm Doing It Wrong™, how do I do this correctly?

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• Maya is lagging in a specific way...?

  - by Aerovistae

  My Maya installation worked perfectly. It is not my computer. Something caused it to stop working overnight, somehow. When I try to drag a vertex or something like that, it moves the vertex, but then I have to click like 3 times somewhere outside the mesh before the actual mesh will catch up and follow the vertex. Until I do that, it just stays as it was, with a floating vertex somewhere inside it or outside it. It makes modeling borderline impossible and completely infuriating. What ought to be happening is what we're all used to-- as I move the vertex, the mesh follows it actively, so I can see what it looks like at every given moment until I release the vertex in its new position. Other weird thing: this only applies to complex meshes, like a couple thousand faces. A simple cube works fine. What gives?? Anybody?

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