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  • Logic / Render phases with a single thread

    - by DevilWithin
    The question I have may generate different opinions from different developers, but I'd still like to have an answer on this. Its all about the updating and rendering steps of the game loop, and their use under multi and single threaded environments. Currently, there is one thread running, which takes care of sequentially executing events , logic and rendering. Sometimes, the logic part may wish to change the game state to something else, and in between do some loading of files. The result is that the game hangs completely while loading, and then proceeds to normal rendering of the new state. To go around this, i could make another thread, do the loading there while the main thread renders a smooth loading animation, and then proceed normally. The real question is about if i don't create another thread. I could refresh the screen from the logic thread, and provide some basic loading screen, which could be not so smoothly updated while the files load. In fact, this approach is not loved by a lot of developers, as it scrambles render code in the logic step, which may cause problems of different sorts.. Hope its clear!

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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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  • Blending transition in cocos2d

    - by fiddler
    In my cocos2d-iphone game, I have 2 backgrounds (CCnodes), each containing a quite complex hierarchy of sprites. I would like to make a smooth transition between them: initially, only the first background is visible at the end, only the second one is visible Is there a good way to set the opacity of a full hierarchy of sprites ? I tried to recursively set the opacity of all the contained sprites. It kinda works except that: i guess it's not very efficient i would like the opacity of overlapping sprites to be 'merged' (as if the background was one single big sprite)

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  • cocos2d-x simple shader usage [on hold]

    - by Narek
    I want to obtain color ramp effect from this tutorial: http://www.raywenderlich.com/10862/how-to-create-cool-effects-with-custom-shaders-in-opengl-es-2-0-and-cocos2d-2-x Here is my code in cocos2d-x 3: bool HelloWorld::init() { ////////////////////////////// // 1. super init first if ( !Layer::init() ) { return false; } Vec2 origin = Director::getInstance()->getVisibleOrigin(); sprite = Sprite::create("HelloWorld.png"); sprite->setAnchorPoint(Vec2(0, 0)); sprite->setRotation(3); sprite->setPosition(origin); addChild(sprite); std::string str = FileUtils::getInstance()->getStringFromFile("CSEColorRamp.fsh"); const GLchar * fragmentSource = str.c_str(); GLProgram* p = GLProgram::createWithByteArrays(ccPositionTextureA8Color_vert, fragmentSource); p->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_POSITION); p->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORD); p->link(); p->updateUniforms(); sprite->setGLProgram(p); // 3 colorRampUniformLocation = glGetUniformLocation(sprite->getGLProgram()->getProgram(), "u_colorRampTexture"); glUniform1i(colorRampUniformLocation, 1); // 4 colorRampTexture = Director::getInstance()->getTextureCache()->addImage("colorRamp.png"); colorRampTexture->setAliasTexParameters(); // 5 sprite->getGLProgram()->use(); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, colorRampTexture->getName()); glActiveTexture(GL_TEXTURE0); return true; } And here is the fragment shader as it is in the tutorial: #ifdef GL_ES precision mediump float; #endif // 1 varying vec2 v_texCoord; uniform sampler2D u_texture; uniform sampler2D u_colorRampTexture; void main() { // 2 vec3 normalColor = texture2D(u_texture, v_texCoord).rgb; // 3 float rampedR = texture2D(u_colorRampTexture, vec2(normalColor.r, 0)).r; float rampedG = texture2D(u_colorRampTexture, vec2(normalColor.g, 0)).g; float rampedB = texture2D(u_colorRampTexture, vec2(normalColor.b, 0)).b; // 4 gl_FragColor = vec4(rampedR, rampedG, rampedB, 1); } As a result I get a black screen with 2 draw calls. What is wrong? Do I miss something?

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  • 3D architecture app for Android or iPhone

    - by Manixate
    I want to make an app for 3D modeling on iPhone/Android. I cannot get the basic idea of how to get started. I have various options such as learning OpenGL ES, UDK or Unity3d but I want to create models(e.g architecture etc) in my app and then render them when user is finished modeling. I do not know if I am able to design models and then render them in the same app with various effects on the iPhone/Android using UDK or Unity3d. (Note: If you find this question unclear please ask, I may have skipped some vital information).

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  • Making a game with responsive resolution

    - by alexandervrs
    I am making a game, however I wish for it to be resolution agnostic. My target resolution i.e. where things look as intended is 1600 x 900. My ideas are: Make the HUD stay fixed to the sides no matter what resolution, use different size for HUD graphics under a certain resolution and another under a certain large one. Use large HD sprites/backgrounds which are a power of 2, so they scale nicely. Use the player's native resolution. Scale the game area (not the HUD) to fit (resulting zooming in some and cropping the game area sides if necessary for widescreen, no stretch), but always fill the screen. Have a min and max resolution limit for small and very large displays where you will just change the resolution(?) or scale up/down to fit. What I am a bit confused though is what math formula I would use to scale the game area correctly based on the resolution no matter the aspect ratio, fully fit in a square screen and with some clip to the sides for widescreen. Pseudocode would help as well. :)

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  • Java Slick2d - Mouse picking how to take into account camera

    - by Corey
    When I move it it obviously changes the viewport so my mouse picking is off. My camera is just a float x and y and I use g.translate(-cam.cameraX+400, -cam.cameraY+300); to translate the graphics. I have the numbers hard coded just for testing purposes. How would I take into account the camera so my mouse picking works correctly. 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) { if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } That is my mouse picking code

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  • Does anybody know of any resources to achieve this particular "2.5D" isometric engine effect?

    - by Craig Whitley
    I understand this is a little vague, but I was hoping somebody might be able to describe a high-level workflow or link to a resource to be able to achieve a specific isometric "2.5D" tile engine effect. I fell in love with http://www.youtube.com/watch?v=-Q6ISVaM5Ww this engine. Especially with the lighting and the shaders! He has a brief description of how he achieved what he did, but I could really use a brief flow of where you would start, what you would read up on and learn and the logical order to implement these things. A few specific questions: 1) Is there a heightmap on the ground texture that lets the light reflect brighter on certain parts of it? 2) "..using a special material which calculates the world-space normal vectors of every pixel.." - is this some "magic" special material he has created himself, or can you hazard a guess at what he means? 3) with relation to the above quote - what does he mean by 'world-space normal vectors of every pixel'? 4) I'm guessing I'm being a little bit optimistic when I ask if there's any 'all-in-one' tutorial out there? :)

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  • What are the pro/cons of Unity3D as a choice to make games?

    - by jokoon
    We are doing our school project with Unity3d, since they were using Shiva the previous year (which seems horrible to me), and I wanted to know your point of view for this tool. Pros: multi platform, I even heard Google is going to implement it in Chrome everything you need is here scripting languages makes it a good choice for people who are not programming gurus Cons: multiplayer ? proprietary, you are totally dependent of unity and its limit and can't extend it it's less "making a game from scratch" C++ would have been a cool thing I really think this kind of tool is interesting, but is it worth it to use at school for a project that involves more than 3 programming persons ? What do we really learn in term of programming from using this kind of tool (I'm ok with python and js, but I hate C#) ? We could have use Ogre instead, even if we were learning direct x starting january...

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  • Examples of good Javascript/HTML5 based games

    - by Zuch
    Now that Flash is largely being replaced with HTML5 elements (video, audio, canvas, etc.) are there any good examples of web-based games built on completely open standards (meaning Javascript, HTML and CSS)? I see a lot of examples of pure HTML5 implementations of what was once only in Flash (like stuff here: http://www.html5rocks.com/) but not many games, a domain which still seem dominated by Flash. I'm curious what's possible and what the limitations are.

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  • Marmalade SDK views navigation concepts

    - by Mina Samy
    I want to develop a simple multi-Activity Android game using Marmalade SDK. I looked at the SDK samples and found that most of them are a single view (Android Activity) apps. The Navigation model in Android is a stack-like model where views are pushed and popped. I can't find whether Marmalade has a similar model or it uses a different approach. would you please explain this to me and provide tutorials and samples to navigation in Marmalade if possible ? Thanks

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  • Java Animation Memory Overload [on hold]

    - by user2425429
    I need a way to reduce the memory usage of these programs while keeping the functionality. Every time I add 50 milliseconds or so to the set&display loop in AnimationTest1, it throws an out of memory error. Here is the code I have now: import java.awt.DisplayMode; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Polygon; import java.util.ArrayList; import java.util.List; import java.util.concurrent.Executor; import java.util.concurrent.Executors; import javax.swing.ImageIcon; public class AnimationTest1 { public static void main(String args[]) { AnimationTest1 test = new AnimationTest1(); test.run(); } private static final DisplayMode POSSIBLE_MODES[] = { new DisplayMode(800, 600, 32, 0), new DisplayMode(800, 600, 24, 0), new DisplayMode(800, 600, 16, 0), new DisplayMode(640, 480, 32, 0), new DisplayMode(640, 480, 24, 0), new DisplayMode(640, 480, 16, 0) }; private static final long DEMO_TIME = 4000; private ScreenManager screen; private Image bgImage; private Animation anim; public void loadImages() { // create animation List<Polygon> polygons=new ArrayList(); int[] x=new int[]{20,4,4,20,40,56,56,40}; int[] y=new int[]{20,32,40,44,44,40,32,20}; polygons.add(new Polygon(x,y,8)); anim = new Animation(); //# of frames long startTime = System.currentTimeMillis(); long currTimer = startTime; long elapsedTime = 0; boolean animated = false; Graphics2D g = screen.getGraphics(); int width=200; int height=200; //set&display loop while (currTimer - startTime < DEMO_TIME*2) { //draw the polygons if(!animated){ for(int j=0; j<polygons.size();j++){ for(int pos=0; pos<polygons.get(j).npoints; pos++){ polygons.get(j).xpoints[pos]+=1; } } anim.setNewPolyFrame(polygons , width , height , 64); } else{ // update animation anim.update(elapsedTime); draw(g); g.dispose(); screen.update(); try{ Thread.sleep(20); } catch(InterruptedException ie){} } if(currTimer - startTime == DEMO_TIME) animated=true; elapsedTime = System.currentTimeMillis() - currTimer; currTimer += elapsedTime; } } public void run() { screen = new ScreenManager(); try { DisplayMode displayMode = screen.findFirstCompatibleMode(POSSIBLE_MODES); screen.setFullScreen(displayMode); loadImages(); } finally { screen.restoreScreen(); } } public void draw(Graphics g) { // draw background g.drawImage(bgImage, 0, 0, null); // draw image g.drawImage(anim.getImage(), 0, 0, null); } } ScreenManager: import java.awt.Color; import java.awt.DisplayMode; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GraphicsConfiguration; import java.awt.GraphicsDevice; import java.awt.GraphicsEnvironment; import java.awt.Toolkit; import java.awt.Window; import java.awt.event.KeyListener; import java.awt.event.MouseListener; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; import javax.swing.JPanel; public class ScreenManager extends JPanel { private GraphicsDevice device; /** Creates a new ScreenManager object. */ public ScreenManager() { GraphicsEnvironment environment=GraphicsEnvironment.getLocalGraphicsEnvironment(); device = environment.getDefaultScreenDevice(); setBackground(Color.white); } /** Returns a list of compatible display modes for the default device on the system. */ public DisplayMode[] getCompatibleDisplayModes() { return device.getDisplayModes(); } /** Returns the first compatible mode in a list of modes. Returns null if no modes are compatible. */ public DisplayMode findFirstCompatibleMode( DisplayMode modes[]) { DisplayMode goodModes[] = device.getDisplayModes(); for (int i = 0; i < modes.length; i++) { for (int j = 0; j < goodModes.length; j++) { if (displayModesMatch(modes[i], goodModes[j])) { return modes[i]; } } } return null; } /** Returns the current display mode. */ public DisplayMode getCurrentDisplayMode() { return device.getDisplayMode(); } /** Determines if two display modes "match". Two display modes match if they have the same resolution, bit depth, and refresh rate. The bit depth is ignored if one of the modes has a bit depth of DisplayMode.BIT_DEPTH_MULTI. Likewise, the refresh rate is ignored if one of the modes has a refresh rate of DisplayMode.REFRESH_RATE_UNKNOWN. */ public boolean displayModesMatch(DisplayMode mode1, DisplayMode mode2) { if (mode1.getWidth() != mode2.getWidth() || mode1.getHeight() != mode2.getHeight()) { return false; } if (mode1.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && mode2.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && mode1.getBitDepth() != mode2.getBitDepth()) { return false; } if (mode1.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && mode2.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && mode1.getRefreshRate() != mode2.getRefreshRate()) { return false; } return true; } /** Enters full screen mode and changes the display mode. If the specified display mode is null or not compatible with this device, or if the display mode cannot be changed on this system, the current display mode is used. <p> The display uses a BufferStrategy with 2 buffers. */ public void setFullScreen(DisplayMode displayMode) { JFrame frame = new JFrame(); frame.setUndecorated(true); frame.setIgnoreRepaint(true); frame.setResizable(true); device.setFullScreenWindow(frame); if (displayMode != null && device.isDisplayChangeSupported()) { try { device.setDisplayMode(displayMode); } catch (IllegalArgumentException ex) { } } frame.createBufferStrategy(2); Graphics g=frame.getGraphics(); g.setColor(Color.white); g.drawRect(0, 0, frame.WIDTH, frame.HEIGHT); frame.paintAll(g); g.setColor(Color.black); g.dispose(); } /** Gets the graphics context for the display. The ScreenManager uses double buffering, so applications must call update() to show any graphics drawn. <p> The application must dispose of the graphics object. */ public Graphics2D getGraphics() { Window window = device.getFullScreenWindow(); if (window != null) { BufferStrategy strategy = window.getBufferStrategy(); return (Graphics2D)strategy.getDrawGraphics(); } else { return null; } } /** Updates the display. */ public void update() { Window window = device.getFullScreenWindow(); if (window != null) { BufferStrategy strategy = window.getBufferStrategy(); if (!strategy.contentsLost()) { strategy.show(); } } // Sync the display on some systems. // (on Linux, this fixes event queue problems) Toolkit.getDefaultToolkit().sync(); } /** Returns the window currently used in full screen mode. Returns null if the device is not in full screen mode. */ public Window getFullScreenWindow() { return device.getFullScreenWindow(); } /** Returns the width of the window currently used in full screen mode. Returns 0 if the device is not in full screen mode. */ public int getWidth() { Window window = device.getFullScreenWindow(); if (window != null) { return window.getWidth(); } else { return 0; } } /** Returns the height of the window currently used in full screen mode. Returns 0 if the device is not in full screen mode. */ public int getHeight() { Window window = device.getFullScreenWindow(); if (window != null) { return window.getHeight(); } else { return 0; } } /** Restores the screen's display mode. */ public void restoreScreen() { Window window = device.getFullScreenWindow(); if (window != null) { window.dispose(); } device.setFullScreenWindow(null); } /** Creates an image compatible with the current display. */ public BufferedImage createCompatibleImage(int w, int h, int transparency) { Window window = device.getFullScreenWindow(); if (window != null) { GraphicsConfiguration gc = window.getGraphicsConfiguration(); return gc.createCompatibleImage(w, h, transparency); } return null; } } Animation: import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Polygon; import java.awt.image.BufferedImage; import java.util.ArrayList; import java.util.List; /** The Animation class manages a series of images (frames) and the amount of time to display each frame. */ public class Animation { private ArrayList frames; private int currFrameIndex; private long animTime; private long totalDuration; /** Creates a new, empty Animation. */ public Animation() { frames = new ArrayList(); totalDuration = 0; start(); } /** Adds an image to the animation with the specified duration (time to display the image). */ public synchronized void addFrame(BufferedImage image, long duration){ ScreenManager s = new ScreenManager(); totalDuration += duration; frames.add(new AnimFrame(image, totalDuration)); } /** Starts the animation over from the beginning. */ public synchronized void start() { animTime = 0; currFrameIndex = 0; } /** Updates the animation's current image (frame), if necessary. */ public synchronized void update(long elapsedTime) { if (frames.size() >= 1) { animTime += elapsedTime; /*if (animTime >= totalDuration) { animTime = animTime % totalDuration; currFrameIndex = 0; }*/ while (animTime > getFrame(0).endTime) { frames.remove(0); } } } /** Gets the Animation's current image. Returns null if this animation has no images. */ public synchronized Image getImage() { if (frames.size() > 0&&!(currFrameIndex>=frames.size())) { return getFrame(currFrameIndex).image; } else{ System.out.println("There are no frames!"); System.exit(0); } return null; } private AnimFrame getFrame(int i) { return (AnimFrame)frames.get(i); } private class AnimFrame { Image image; long endTime; public AnimFrame(Image image, long endTime) { this.image = image; this.endTime = endTime; } } public void setNewPolyFrame(List<Polygon> polys,int imagewidth,int imageheight,int time){ BufferedImage image=new BufferedImage(imagewidth, imageheight, 1); Graphics g=image.getGraphics(); for(int i=0;i<polys.size();i++){ g.drawPolygon(polys.get(i)); } addFrame(image,time); g.dispose(); } }

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  • Does XNA/MonoGame have a text caching mechanism, or has an open source one been implemented?

    - by Casey
    I'm playing around with MonoGame, and I've noticed the SpriteFont class draws static text very inefficiently. Each time the text is drawn the spacing is recalculated. This isn't a big deal on my quad core PC, but on mobile applications it might be a problem. Before I go and program some text which caches the arrangement of its letters in an array and then feeds that array to the SpriteBatch, I would like to make sure there isn't something available to do this already, either in MonoGame itself or a class someone has implemented and made available for general use.

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  • SDL mouse wheel not picking up

    - by Chris
    Running Ubuntu 11.04, SDL 1.2 trying to pickup mouse wheel up/down movement with this (stripped down) code: int main( int argc, char **argv ) { SDL_MouseButtonEvent *mousebutton = NULL; while ( !done ) { if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_LEFT) yrot += 0.75f; else if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_RIGHT) yrot -= 0.75f; else if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_WHEELUP){ xrot += 0.75f; }else if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_WHEELDOWN){ xrot -= 0.75f; } while ( SDL_PollEvent( &event ) ) { switch( event.type ) { case SDL_MOUSEBUTTONDOWN: mousebutton = &event.button; break; case SDL_MOUSEBUTTONUP: mousebutton = NULL; break; default: break; } } } return 0; } strange thing is, scrolling with the mouse button does nothing, but if I hold down a mouse button or two and then move the mouse it hits the SDL_BUTTON_WHEEL code occasionally. This honestly reeks of a pointer issue, which would make sense since I've been spoiled with C# for the past couple years, but I am just not seeing it. How do i correctly find mouse scroll events in SDL?

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  • Rotating a cube using jBullet collisions

    - by Kenneth Bray
    How would one go about rotating/flipping a cube with the physics of jBullet? Here is my Draw method for my cube object: public void Draw() { // center point posX, posY, posZ float radius = .25f;//size / 2; glPushMatrix(); glBegin(GL_QUADS); //top { glColor3f(5.0f,1.0f,5.0f); // white glVertex3f(posX + radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY + radius, posZ + radius); } //bottom { glColor3f(1.0f,1.0f,0.0f); // ?? color glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY - radius, posZ - radius); } //right side { glColor3f(1.0f,0.0f,1.0f); // ?? color glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } //left side { glColor3f(0.0f,1.0f,1.0f); // ?? color glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); } //front side { glColor3f(0.0f,0.0f,1.0f); // blue glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); } //back side { glColor3f(0.0f,1.0f,0.0f); // green glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } glEnd(); glPopMatrix(); Update(); } This is my update method for the cube position: public void Update() { Transform trans = new Transform(); cubeRigidBody.getMotionState().getWorldTransform(trans); posX = trans.origin.x; posY = trans.origin.y; posZ = trans.origin.z; Quat4f outRot = new Quat4f(); trans.getRotation(outRot); rotX = outRot.x; rotY = outRot.y; rotZ = outRot.z; rotW = outRot.w; } I am assuming I need to use glrotatef, but it does not seem to work at all when I try that.. this is how I have tried to rotate the cubes: GL11.glRotatef(rotW, rotX, 0.0f, 0.0f); GL11.glRotatef(rotW, 0.0f, rotY, 0.0f); GL11.glRotatef(rotW, 0.0f, 0.0f, rotZ);

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  • Problems with SAT Collision Detection

    - by DJ AzKai
    I'm doing a project in one of my modules for college in C++ with SFML and I was hoping someone may be able to help me. I'm using a vector of squares and triangles and I am using the SAT collision detection method to see if objects collide and to make the objects respond to the collision appropriately using the MTV(minimum translation vector) Below is my code: //from the main method int main(){ // Create the main window sf::RenderWindow App(sf::VideoMode(800, 600, 32), "SFML OpenGL"); // Create a clock for measuring time elapsed sf::Clock Clock; srand(time(0)); //prepare OpenGL surface for HSR glClearDepth(1.f); glClearColor(0.3f, 0.3f, 0.3f, 0.f); //background colour glEnable(GL_DEPTH_TEST); glDepthMask(GL_TRUE); //// Setup a perspective projection & Camera position glMatrixMode(GL_PROJECTION); glLoadIdentity(); //set up a 3D Perspective View volume //gluPerspective(90.f, 1.f, 1.f, 300.0f);//fov, aspect, zNear, zFar //set up a orthographic projection same size as window //this mease the vertex coordinates are in pixel space glOrtho(0,800,0,600,0,1); // use pixel coordinates // Finally, display rendered frame on screen vector<BouncingThing*> triangles; for(int i = 0; i < 10; i++) { //instantiate each triangle; triangles.push_back(new BouncingTriangle(Vector2f(rand() % 700, rand() % 500), 3)); } vector<BouncingThing*> boxes; for(int i = 0; i < 10; i++) { //instantiate each box; boxes.push_back(new BouncingBox(Vector2f(rand() % 700, rand() % 500), 4)); } CollisionDetection * b = new CollisionDetection(); // Start game loop while (App.isOpen()) { // Process events sf::Event Event; while (App.pollEvent(Event)) { // Close window : exit if (Event.type == sf::Event::Closed) App.close(); // Escape key : exit if ((Event.type == sf::Event::KeyPressed) && (Event.key.code == sf::Keyboard::Escape)) App.close(); } //Prepare for drawing // Clear color and depth buffer glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Apply some transformations glMatrixMode(GL_MODELVIEW); glLoadIdentity(); for(int i = 0; i < 10; i++) { triangles[i]->draw(); boxes[i]->draw(); triangles[i]->update(Vector2f(800,600)); boxes[i]->draw(); boxes[i]->update(Vector2f(800,600)); } for(int j = 0; j < 10; j++) { for(int i = 0; i < 10; i++) { triangles[j]->setCollision(b->CheckCollision(*(triangles[j]),*(boxes[i]))); } } for(int j = 0; j < 10; j++) { for(int i = 0; i < 10; i++) { boxes[j]->setCollision(b->CheckCollision(*(boxes[j]),*(triangles[i]))); } } for(int i = 0; i < triangles.size(); i++) { for(int j = i + 1; j < triangles.size(); j ++) { triangles[j]->setCollision(b->CheckCollision(*(triangles[j]),*(triangles[i]))); } } for(int i = 0; i < triangles.size(); i++) { for(int j = i + 1; j < triangles.size(); j ++) { boxes[j]->setCollision(b->CheckCollision(*(boxes[j]),*(boxes[i]))); } } App.display(); } return EXIT_SUCCESS; } (ignore this line) //from the BouncingThing.cpp BouncingThing::BouncingThing(Vector2f position, int noSides) : pos(position), pi(3.14), radius(3.14), nSides(noSides) { collided = false; if(nSides ==3) { Vector2f vert1 = Vector2f(-12.0f,-12.0f); Vector2f vert2 = Vector2f(0.0f, 12.0f); Vector2f vert3 = Vector2f(12.0f,-12.0f); verts.push_back(vert1); verts.push_back(vert2); verts.push_back(vert3); } else if(nSides == 4) { Vector2f vert1 = Vector2f(-12.0f,12.0f); Vector2f vert2 = Vector2f(12.0f, 12.0f); Vector2f vert3 = Vector2f(12.0f,-12.0f); Vector2f vert4 = Vector2f(-12.0f, -12.0f); verts.push_back(vert1); verts.push_back(vert2); verts.push_back(vert3); verts.push_back(vert4); } velocity.x = ((rand() % 5 + 1) / 3) + 1; velocity.y = ((rand() % 5 + 1) / 3 ) +1; } void BouncingThing::update(Vector2f screenSize) { Transform t; t.rotate(0); for(int i=0;i< verts.size(); i++) { verts[i]=t.transformPoint(verts[i]); } if(pos.x >= screenSize.x || pos.x <= 0) { velocity.x *= -1; } if(pos.y >= screenSize.y || pos.y <= 0) { velocity.y *= -1; } if(collided) { //velocity.x *= -1; //velocity.y *= -1; collided = false; } pos += velocity; } void BouncingThing::setCollision(bool x){ collided = x; } void BouncingThing::draw() { glBegin(GL_POLYGON); glColor3f(0,1,0); for(int i = 0; i < verts.size(); i++) { glVertex2f(pos.x + verts[i].x,pos.y + verts[i].y); } glEnd(); } vector<Vector2f> BouncingThing::getNormals() { vector<Vector2f> normalVerts; if(nSides == 3) { Vector2f ab = Vector2f((verts[1].x + pos.x) - (verts[0].x + pos.x), (verts[1].y + pos.y) - (verts[0].y + pos.y)); ab = flip(ab); ab.x *= -1; normalVerts.push_back(ab); Vector2f bc = Vector2f((verts[2].x + pos.x) - (verts[1].x + pos.x), (verts[2].y + pos.y) - (verts[1].y + pos.y)); bc = flip(bc); bc.x *= -1; normalVerts.push_back(bc); Vector2f ac = Vector2f((verts[2].x + pos.x) - (verts[0].x + pos.x), (verts[2].y + pos.y) - (verts[0].y + pos.y)); ac = flip(ac); ac.x *= -1; normalVerts.push_back(ac); return normalVerts; } if(nSides ==4) { Vector2f ab = Vector2f((verts[1].x + pos.x) - (verts[0].x + pos.x), (verts[1].y + pos.y) - (verts[0].y + pos.y)); ab = flip(ab); ab.x *= -1; normalVerts.push_back(ab); Vector2f bc = Vector2f((verts[2].x + pos.x) - (verts[1].x + pos.x), (verts[2].y + pos.y) - (verts[1].y + pos.y)); bc = flip(bc); bc.x *= -1; normalVerts.push_back(bc); return normalVerts; } } Vector2f BouncingThing::flip(Vector2f v){ float vyTemp = v.x; float vxTemp = v.y * -1; return Vector2f(vxTemp, vyTemp); } (Ignore this line) CollisionDetection::CollisionDetection() { } vector<float> CollisionDetection::bubbleSort(vector<float> w) { int temp; bool finished = false; while (!finished) { finished = true; for (int i = 0; i < w.size()-1; i++) { if (w[i] > w[i+1]) { temp = w[i]; w[i] = w[i+1]; w[i+1] = temp; finished=false; } } } return w; } class Vector{ public: //static int dp_count; static float dot(sf::Vector2f a,sf::Vector2f b){ //dp_count++; return a.x*b.x+a.y*b.y; } static float length(sf::Vector2f a){ return sqrt(a.x*a.x+a.y*a.y); } static Vector2f add(Vector2f a, Vector2f b) { return Vector2f(a.x + b.y, a.y + b.y); } static sf::Vector2f getNormal(sf::Vector2f a,sf::Vector2f b){ sf::Vector2f n; n=a-b; n/=Vector::length(n);//normalise float x=n.x; n.x=n.y; n.y=-x; return n; } }; bool CollisionDetection::CheckCollision(BouncingThing & x, BouncingThing & y) { vector<Vector2f> xVerts = x.getVerts(); vector<Vector2f> yVerts = y.getVerts(); vector<Vector2f> xNormals = x.getNormals(); vector<Vector2f> yNormals = y.getNormals(); int size; vector<float> xRange; vector<float> yRange; for(int j = 0; j < xNormals.size(); j++) { Vector p; for(int i = 0; i < xVerts.size(); i++) { xRange.push_back(p.dot(xNormals[j], Vector2f(xVerts[i].x, xVerts[i].x))); } for(int i = 0; i < yVerts.size(); i++) { yRange.push_back(p.dot(xNormals[j], Vector2f(yVerts[i].x , yVerts[i].y))); } yRange = bubbleSort(yRange); xRange = bubbleSort(xRange); if(xRange[xRange.size() - 1] < yRange[0] || yRange[yRange.size() - 1] < xRange[0]) { return false; } float x3 = Min(xRange[0], yRange[0]); float y3 = Max(xRange[xRange.size() - 1], yRange[yRange.size() - 1]); float length = Max(x3, y3) - Min(x3, y3); } for(int j = 0; j < yNormals.size(); j++) { Vector p; for(int i = 0; i < xVerts.size(); i++) { xRange.push_back(p.dot(yNormals[j], xVerts[i])); } for(int i = 0; i < yVerts.size(); i++) { yRange.push_back(p.dot(yNormals[j], yVerts[i])); } yRange = bubbleSort(yRange); xRange = bubbleSort(xRange); if(xRange[xRange.size() - 1] < yRange[0] || yRange[yRange.size() - 1] < xRange[0]) { return false; } } return true; } float CollisionDetection::Min(float min, float max) { if(max < min) { min = max; } else return min; } float CollisionDetection::Max(float min, float max) { if(min > max) { max = min; } else return min; } On the screen the objects will freeze for a small amount of time before moving off again. However the problem is is that when this happens there are no collisions actually happening and I would really love to find out where the flaw is in the code. If you need any more information/code please don't hesitate to ask and I'll reply as soon as possible Regards, AzKai

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  • Check for bodies within a specific circle in Box2D

    - by ltjax
    I'm trying to find positions to insert new bodies into my world. For that, I'd like to have a "free" spot where this body wouldn't overlap with anything else. So my plan was to sample "random" positions and check whether they overlap with my "potential" new body. Since my bodies are always circular, I'd need to test within a given circle. So far, the only way to use box2d for this seems to use b2World::QueryAABB around my circle and manually doing an overlap test with all the fixtures it gives me (Box2D doesn't event seem to allow me to tap into its overlapping tests?!). It seems to me like Box2D should already provide such functionality - is there a way that lets me do this without reinventing most of the wheel again?

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  • Reversi/Othello early-game evaluation function

    - by Vladislav Il'ushin
    I've written my own Reversi player, based on the MiniMax algorithm, with Alpha-Beta pruning, but in the first 10 moves my evaluation function is too slow. I need a good early-game evaluation function. I'm trying to do it with this matrix (corresponding to the board) which determines how favourable that square is to have: { 30, -25, 10, 5, 5, 10, -25, 30,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 30, -25, 10, 5, 5, 10, -25, 30,},}; But it doesn't work well. Have you even written an early-game evaluation function for Reversi?

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  • Class Design - Space Simulator

    - by Peteyslatts
    I have pretty much taught myself everything I know about programming, so while I know how to teach myself (books, internet and reading API's), I'm finding that there hasn't been a whole lot in the way of good programming. So I have two questions: First the broad one: Does anyone have suggestions as to sources for learning about good programming habits and techniques? I'd prefer it if the resource wasn't a 5000 page tome. The more I can read it in installments the better. More specifically: I am finishing up learning the basics of XNA and I want to create a space simulator to test my knowledge. This isn't a full scale simulator, but just something that covers everything I learned. It's also going to be modular so I can build on it, after I get the basics down. One of the early features I want to implement is AI. And I want to take this into account as I'm designing my classes so I can minimize rewriting code. So my question: How should I design ship classes so that both the player and AI can use them? The only idea I have so far is: Create a ship class that contains stats, models, textures, collision data etc. The player and AI would then have the data for position, rotation, health, etc and would base their status off of the ship stats.

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  • Why does my code dividing a 2D array into chunks fail?

    - by Borog
    I have a 2D-Array representing my world. I want to divide this huge thing into smaller chunks to make collision detection easier. I have a Chunk class that consists only of another 2D Array with a specific width and height and I want to iterate through the world, create new Chunks and add them to a list (or maybe a Map with Coordinates as the key; we'll see about that). world = new World(8192, 1024); Integer[][] chunkArray; for(int a = 0; a < map.getHeight() / Chunk.chunkHeight; a++) { for(int b = 0; b < map.getWidth() / Chunk.chunkWidth; b++) { Chunk chunk = new Chunk(); chunkArray = new Integer[Chunk.chunkWidth][Chunk.chunkHeight]; for(int x = Chunk.chunkHeight*a; x < Chunk.chunkHeight*(a+1); x++) { for(int y = Chunk.chunkWidth*b; y < Chunk.chunkWidth*(b+1); y++) { // Yes, the tileMap actually is [height][width] I'll have // to fix that somewhere down the line -.- chunkArray[y][x] = map.getTileMap()[x*a][y*b]; // TODO:Attach to chunk } } chunkList.add(chunk); } } System.out.println(chunkList.size()); The two outer loops get a new chunk in a specific row and column. I do that by dividing the overall size of the map by the chunkSize. The inner loops then fill a new chunkArray and attach it to the chunk. But somehow my maths is broken here. Let's assume the chunkHeight = chunkWidth = 64. For the first Array I want to start at [0][0] and go until [63][63]. For the next I want to start at [64][64] and go until [127][127] and so on. But I get an out of bounds exception and can't figure out why. Any help appreciated! Actually I think I know where the problem lies: chunkArray[y][x] can't work, because y goes from 0-63 just in the first iteration. Afterwards it goes from 64-127, so sure it is out of bounds. Still no nice solution though :/ EDIT: if(y < Chunk.chunkWidth && x < Chunk.chunkHeight) chunkArray[y][x] = map.getTileMap()[y][x]; This works for the first iteration... now I need to get the commonly accepted formula.

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  • Calculating up-vector to avoid gimbal lock using euler angles

    - by jessejuicer
    I wish to orbit a camera around a sphere, yet the problem is that when the camera rotates so that it is at the north pole (and pointing down) or the south pole (and pointing up) of the sphere the camera doesn't handle itself very well. It spins rapidly until arriving 180 degrees in the opposite direction. I believe this is known as gimbal lock. I understand you can avoid this problem using quaternions. But I also read in another forum that it's possible to avoid this easily using euler angles as well. Which I would prefer to do. It was said that all you need to do is "calculate a proper up-vector every frame, and that avoids the problem entirely." Well, I tried aligning the up-vector with the vertical axis of the camera whenever the camera changed orientation, but this didn't seem to work. Meaning that the up-vector followed exactly the orientation of the camera's y-axis (or it's up vector), instead of using a constant up-vector aligned to the up-vector of the world (0, 1, 0). How exactly do I go about calculating a proper up-vector as my camera orientation changes to avoid the gimbal lock problem mentioned above?

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  • GLSL: Strange light reflections

    - by Tom
    According to this tutorial I'm trying to make a normal mapping using GLSL, but something is wrong and I can't find the solution. The output render is in this image: Image1 in this image is a plane with two triangles and each of it is different illuminated (that is bad). The plane has 6 vertices. In the upper left side of this plane are 2 identical vertices (same in the lower right). Here are some vectors same for each vertice: normal vector = 0, 1, 0 (red lines on image) tangent vector = 0, 0,-1 (green lines on image) bitangent vector = -1, 0, 0 (blue lines on image) here I have one question: The two identical vertices does need to have the same tangent and bitangent? I have tried to make other values to the tangents but the effect was still similar. Here are my shaders Vertex shader: #version 130 // Input vertex data, different for all executions of this shader. in vec3 vertexPosition_modelspace; in vec2 vertexUV; in vec3 vertexNormal_modelspace; in vec3 vertexTangent_modelspace; in vec3 vertexBitangent_modelspace; // Output data ; will be interpolated for each fragment. out vec2 UV; out vec3 Position_worldspace; out vec3 EyeDirection_cameraspace; out vec3 LightDirection_cameraspace; out vec3 LightDirection_tangentspace; out vec3 EyeDirection_tangentspace; // Values that stay constant for the whole mesh. uniform mat4 MVP; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // Position of the vertex, in worldspace : M * position Position_worldspace = (M * vec4(vertexPosition_modelspace,1)).xyz; // Vector that goes from the vertex to the camera, in camera space. // In camera space, the camera is at the origin (0,0,0). vec3 vertexPosition_cameraspace = ( V * M * vec4(vertexPosition_modelspace,1)).xyz; EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace; // Vector that goes from the vertex to the light, in camera space. M is ommited because it's identity. vec3 LightPosition_cameraspace = ( V * vec4(LightPosition_worldspace,1)).xyz; LightDirection_cameraspace = LightPosition_cameraspace + EyeDirection_cameraspace; // UV of the vertex. No special space for this one. UV = vertexUV; // model to camera = ModelView vec3 vertexTangent_cameraspace = MV3x3 * vertexTangent_modelspace; vec3 vertexBitangent_cameraspace = MV3x3 * vertexBitangent_modelspace; vec3 vertexNormal_cameraspace = MV3x3 * vertexNormal_modelspace; mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); // You can use dot products instead of building this matrix and transposing it. See References for details. LightDirection_tangentspace = TBN * LightDirection_cameraspace; EyeDirection_tangentspace = TBN * EyeDirection_cameraspace; } Fragment shader: #version 130 // Interpolated values from the vertex shaders in vec2 UV; in vec3 Position_worldspace; in vec3 EyeDirection_cameraspace; in vec3 LightDirection_cameraspace; in vec3 LightDirection_tangentspace; in vec3 EyeDirection_tangentspace; // Ouput data out vec3 color; // Values that stay constant for the whole mesh. uniform sampler2D DiffuseTextureSampler; uniform sampler2D NormalTextureSampler; uniform sampler2D SpecularTextureSampler; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Light emission properties // You probably want to put them as uniforms vec3 LightColor = vec3(1,1,1); float LightPower = 40.0; // Material properties vec3 MaterialDiffuseColor = texture2D( DiffuseTextureSampler, vec2(UV.x,-UV.y) ).rgb; vec3 MaterialAmbientColor = vec3(0.1,0.1,0.1) * MaterialDiffuseColor; //vec3 MaterialSpecularColor = texture2D( SpecularTextureSampler, UV ).rgb * 0.3; vec3 MaterialSpecularColor = vec3(0.5,0.5,0.5); // Local normal, in tangent space. V tex coordinate is inverted because normal map is in TGA (not in DDS) for better quality vec3 TextureNormal_tangentspace = normalize(texture2D( NormalTextureSampler, vec2(UV.x,-UV.y) ).rgb*2.0 - 1.0); // Distance to the light float distance = length( LightPosition_worldspace - Position_worldspace ); // Normal of the computed fragment, in camera space vec3 n = TextureNormal_tangentspace; // Direction of the light (from the fragment to the light) vec3 l = normalize(LightDirection_tangentspace); // Cosine of the angle between the normal and the light direction, // clamped above 0 // - light is at the vertical of the triangle -> 1 // - light is perpendicular to the triangle -> 0 // - light is behind the triangle -> 0 float cosTheta = clamp( dot( n,l ), 0,1 ); // Eye vector (towards the camera) vec3 E = normalize(EyeDirection_tangentspace); // Direction in which the triangle reflects the light vec3 R = reflect(-l,n); // Cosine of the angle between the Eye vector and the Reflect vector, // clamped to 0 // - Looking into the reflection -> 1 // - Looking elsewhere -> < 1 float cosAlpha = clamp( dot( E,R ), 0,1 ); color = // Ambient : simulates indirect lighting MaterialAmbientColor + // Diffuse : "color" of the object MaterialDiffuseColor * LightColor * LightPower * cosTheta / (distance*distance) + // Specular : reflective highlight, like a mirror MaterialSpecularColor * LightColor * LightPower * pow(cosAlpha,5) / (distance*distance); //color.xyz = E; //color.xyz = LightDirection_tangentspace; //color.xyz = EyeDirection_tangentspace; } I have replaced the original color value by EyeDirection_tangentspace vector and then I got other strange effect but I can not link the image (not eunogh reputation) Is it possible that with this shaders is something wrong, or maybe in other place in my code e.g with my matrices? SOLVED Solved... 3 days needed for changing one letter from this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(12*sizeof(float)) // array buffer offset ); to this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(11*sizeof(float)) // array buffer offset ); see difference? :)

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  • Game has noticeable frame drops but when through a profiler it always runs smooth

    - by felipedrl
    I'm trying to optimize my PC game but I can find the bottleneck since every time I run it through a profiler (gDEBugger) it runs smooths. When running outside gDEBugger I get these annoying hiccups. It's not just the graphics, the sound also gets choppy. The drops are inconsistent across runs, i.e, sometimes I run the same scenario and get no drops at all, sometimes I get a few drops, and others the game is consistently slow. The only constant is: when running through gDEBugger I ALWAYS get a smooth run. I'm suspecting something outside my game is interfering and causing these drops, but what in the hell does gDEBugger do that nullifies these drops? A higher process priority? Any ideas? Thanks in advance.

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  • How to remove a box2d body when collision happens?

    - by Ayham
    I’m still new to java and android programming and I am having so much trouble Removing an object when collision happens. I looked around the web and found that I should never handle removing BOX2D bodies during collision detection (a contact listener) and I should add my objects to an arraylist and set a variable in the User Data section of the body to delete or not and handle the removing action in an update handler. So I did this: First I define two ArrayLists one for the faces and one for the bodies: ArrayList<Sprite> myFaces = new ArrayList<Sprite>(); ArrayList<Body> myBodies = new ArrayList<Body>(); Then when I create a face and connect that face to its body I add them to their ArrayLists like this: face = new AnimatedSprite(pX, pY, pWidth, pHeight, this.mBoxFaceTextureRegion); Body BoxBody = PhysicsFactory.createBoxBody(mPhysicsWorld, face, BodyType.DynamicBody, objectFixtureDef); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, BoxBody, true, true)); myFaces.add(face); myBodies.add(BoxBody); now I add a contact listener and an update handler in the onloadscene like this: this.mPhysicsWorld.setContactListener(new ContactListener() { private AnimatedSprite face2; @Override public void beginContact(final Contact pContact) { } @Override public void endContact(final Contact pContact) { } @Override public void preSolve(Contact contact,Manifold oldManifold) { } @Override public void postSolve(Contact contact,ContactImpulse impulse) { } }); scene.registerUpdateHandler(new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(final float pSecondsElapsed) { } }); My plan is to detect which two bodies collided in the contact listener by checking a variable from the user data section of the body, get their numbers in the array list and finally use the update handler to remove these bodies. The questions are: Am I using the arraylist correctly? How to add a variable to the User Data (the code please). I tried removing a body in this update handler but it still throws me NullPointerException , so what is the right way to add an update handler and where should I add it. Any other advices to do this would be great. Thanks in advance.

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  • 2D SAT Collision Detection not working when using certain polygons (With example)

    - by sFuller
    My SAT algorithm falsely reports that collision is occurring when using certain polygons. I believe this happens when using a polygon that does not contain a right angle. Here is a simple diagram of what is going wrong: Here is the problematic code: std::vector<vec2> axesB = polygonB->GetAxes(); //loop over axes B for(int i = 0; i < axesB.size(); i++) { float minA,minB,maxA,maxB; polygonA->Project(axesB[i],&minA,&maxA); polygonB->Project(axesB[i],&minB,&maxB); float intervalDistance = polygonA->GetIntervalDistance(minA, maxA, minB, maxB); if(intervalDistance >= 0) return false; //Collision not occurring } This function retrieves axes from the polygon: std::vector<vec2> Polygon::GetAxes() { std::vector<vec2> axes; for(int i = 0; i < verts.size(); i++) { vec2 a = verts[i]; vec2 b = verts[(i+1)%verts.size()]; vec2 edge = b-a; axes.push_back(vec2(-edge.y,edge.x).GetNormailzed()); } return axes; } This function returns the normalized vector: vec2 vec2::GetNormailzed() { float mag = sqrt( x*x + y*y ); return *this/mag; } This function projects a polygon onto an axis: void Polygon::Project(vec2* axis, float* min, float* max) { float d = axis->DotProduct(&verts[0]); float _min = d; float _max = d; for(int i = 1; i < verts.size(); i++) { d = axis->DotProduct(&verts[i]); _min = std::min(_min,d); _max = std::max(_max,d); } *min = _min; *max = _max; } This function returns the dot product of the vector with another vector. float vec2::DotProduct(vec2* other) { return (x*other->x + y*other->y); } Could anyone give me a pointer in the right direction to what could be causing this bug? Edit: I forgot this function, which gives me the interval distance: float Polygon::GetIntervalDistance(float minA, float maxA, float minB, float maxB) { float intervalDistance; if (minA < minB) { intervalDistance = minB - maxA; } else { intervalDistance = minA - maxB; } return intervalDistance; //A positive value indicates this axis can be separated. } Edit 2: I have recreated the problem in HTML5/Javascript: Demo

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