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• cocos2d event handler not fired when reentering scene

  - by Adam Freund

  I am encountering a very strange problem with my cocos2d app. I add a sprite to the page and have an event handler linked to it which replaces the scene with another scene. On that page I have another button to take me back to the original scene. When I am back on the original scene, the eventHandler doesn't get fired when I click on the sprite. Below is the relevant code. Thanks for any help! CCMenuItemImage *backBtnImg = [CCMenuItemImage itemWithNormalImage:@"btn_back.png" selectedImage:@"btn_back_pressed.png" target:self selector:@selector(backButtonTapped:)]; backBtnImg.position = ccp(45, 286); CCMenu *backBtn = [CCMenu menuWithItems:backBtnImg, nil]; backBtn.position = CGPointZero; [self addChild:backBtn]; EventHandler method (doesn't get called when the scene is re-entered). (void)backButtonTapped:(id)sender { NSLog(@"backButtonTapped\n"); CCMenuItemImage *backButton = (CCMenuItemImage *)sender; [backButton setNormalImage:[CCSprite spriteWithFile:@"btn_back_pressed.png"]]; [[CCDirector sharedDirector] replaceScene:[CCTransitionFade transitionWithDuration:.25 scene:[MenuView scene] withColor:ccBLACK]]; }

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• How do I set an event off when player is on certain tile?

  - by Tom Burman

  Here is the code I use to create and print my map to the canvas: var board = []; function loadMap(map) { if (map == 1) { return [ [2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,3,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,3,0,0,2], [2,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,3,3,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,3,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,3,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,3,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,3,3,3,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,3,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,3,3,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,3,3,3,3,3,3,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2] ]; } } board = loadMap(1); enterfor (y = 0; y <= viewHeight; y++) { for (x = 0; x <= viewWidth; x++) { var theX = x * 32; var theY = y * 32; context.drawImage(mapTiles[board[y+viewY][x+viewX]], theX, theY, 32, 32); } } And here is the code I use for player movement: canvas.addEventListener('keydown', function(e) { console.log(e); var key = null; switch (e.which) { case 37: // Left if (playerX > 0) playerX--; break; case 38: // Up if (playerY > 0) playerY--; break; case 39: // Right if (playerX < worldWidth) playerX++; break; case 40: // Down if (playerY < worldHeight) playerY++; break; } viewX = playerX - Math.floor(0.5 * viewWidth); if (viewX < 0) viewX = 0; if (viewX+viewWidth > worldWidth) viewX = worldWidth - viewWidth; viewY = playerY - Math.floor(0.5 * viewHeight); if (viewY < 0) viewY = 0; if (viewY+viewHeight > worldHeight) viewY = worldHeight - viewHeight; }, false); What I am looking for is a method for when the player lands on tile 3 he loses health. I have tried to use this in the player movement but it doesnt seem to work e.g the left movement: case 37: // Left if (playerX > 0) playerX--; if(board[x2 - 1] == 3) { health--; playerX--; }

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• LWJGL - Mixing 2D and 3D

  - by nathan

  I'm trying to mix 2D and 3D using LWJGL. I have wrote 2D little method that allow me to easily switch between 2D and 3D. protected static void make2D() { glEnable(GL_BLEND); GL11.glMatrixMode(GL11.GL_PROJECTION); GL11.glLoadIdentity(); glOrtho(0.0f, SCREEN_WIDTH, SCREEN_HEIGHT, 0.0f, 0.0f, 1.0f); GL11.glMatrixMode(GL11.GL_MODELVIEW); GL11.glLoadIdentity(); } protected static void make3D() { glDisable(GL_BLEND); GL11.glMatrixMode(GL11.GL_PROJECTION); GL11.glLoadIdentity(); // Reset The Projection Matrix GLU.gluPerspective(45.0f, ((float) SCREEN_WIDTH / (float) SCREEN_HEIGHT), 0.1f, 100.0f); // Calculate The Aspect Ratio Of The Window GL11.glMatrixMode(GL11.GL_MODELVIEW); glLoadIdentity(); } The in my rendering code i would do something like: make2D(); //draw 2D stuffs here make3D(); //draw 3D stuffs here What i'm trying to do is to draw a 3D shape (in my case a quad) and i 2D image. I found this example and i took the code from TextureLoader, Texture and Sprite to load and render a 2D image. Here is how i load the image. TextureLoader loader = new TextureLoader(); Sprite s = new Sprite(loader, "player.png") And how i render it: make2D(); s.draw(0, 0); It works great. Here is how i render my quad: glTranslatef(0.0f, 0.0f, 30.0f); glScalef(12.0f, 9.0f, 1.0f); DrawUtils.drawQuad(); Once again, no problem, the quad is properly rendered. DrawUtils is a simple class i wrote containing utility method to draw primitives shapes. Now my problem is when i want to mix both of the above, loading/rendering the 2D image, rendering the quad. When i try to load my 2D image with the following: s = new Sprite(loader, "player.png); My quad is not rendered anymore (i'm not even trying to render the 2D image at this point). Only the fact of creating the texture create the issue. After looking a bit at the code of Sprite and TextureLoader i found that the problem appears after the call of the glTexImage2d. In the TextureLoader class: glTexImage2D(target, 0, dstPixelFormat, get2Fold(bufferedImage.getWidth()), get2Fold(bufferedImage.getHeight()), 0, srcPixelFormat, GL_UNSIGNED_BYTE, textureBuffer); Commenting this like make the problem disappear. My question is then why? Is there anything special to do after calling this function to do 3D? Does this function alter the render part, the projection matrix?

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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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• What is the best way to implement collision detection using Bullet physics engine and a track generated from a curve?

  - by tigrou

  I am developing a small racing game were the track is generated from a curve. As said above, the track is generated, but not infinite. The track of one level could fit with no problem in memory and will contain a reasonably small amount of triangles. For collisions, I would like to use Bullet physics engine and know what is the best way to handle collisions with the track efficiently. NOTE : The track will be stored as a static rigid body (mass = 0). The player will be represented by a sphere shape for collisions. Here is some possibilities i have in mind : Create one rigid body, then, put all triangles of the track (except non collidable stuff) into it. Result : 1 body with many triangles (eg : 30000 triangles) Split the track into several sections (eg: 10 sections). Then, for each section, create a rigid body and put corresponding triangles in it. Result : small amount of bodies with relatively small amount of triangles (eg : 1500 triangles per section). Split the track into many sub-sections (eg : 1200 sections). Here one subsection = very small step when generating the curve. Again for each sub-section, create a body and put triangles in it. Result : many bodies with very small amount of triangles (eg : 20 triangles). Advantage : it could be possible to "extra data" to each of the subsection, that could be used when handling collisions. Same as 2, but only put sections N and N+1 in physics engine (where N = current section where the player is). When player reach section N+1, unload section N and load section N+2 and so on... Issue : harder to implement, problems if the player suddenly "jump" from one section to another (eg : player fly away from section N, and fall on section N + 4 that was underneath : no collision handled, player will fall into void ) Same as 4, but with many sub-sections. Issues : since subsections are very small there will be constantly new bodies added and removed to physics engine at runtime. Possibilities for player to accidently skip some sections and fall into the void are higher than 4.

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• What does a Game Designer do? what skills do they need?

  - by xenoterracide

  I know someone who is thinking about getting into game design, and I wondered, what does the job game designer entail? what tools do you have to learn how to use? what unique skills do you need? what exactly is it you'd do from day to day. I may be wording this a bit wrong because I'm not sure if the college program is become a game designer or learn game design. but I think the same questions apply either way.

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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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• Isometric smooth fog

  - by marcg11

  I'm working on a simple 2d game with direct3d 9. It's a isometric game with diamond tiles and a staggered map. This is what I have: As you se I have some king of fog which is acomplished by having a fog matrix which is true (clear terrain) or false (obscure terran). But the result is very chunky. The fog moves as the player moves by tiles but not by pixels. Basically I check for every tile if there is fog, if so I just change the color of that tile: if(scene->fog[i+mapx][j+mapy] == FOG_NONE) { tile_color = 0x666666FF; } I also would like the fog to be smoother, for that I followed this "tutorial" but I haven't managed to work it it out. http://www.appsizematters.com/2010/07/how-to-implement-a-fog-of-war-part-2-smooth/

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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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• 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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• 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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• How should I load level data in java?

  - by Matthew G.

  I'm setting up my engine for a certain action/arcade game to have a set of commands that would look something like this. Set landscape to grass Create rocks at ... Create player at X, Y Set goal to "Get to point X Y" Spawn enemy at X, Y I'd then have each object knowing what it has to do, and acting on its own. I've been thinking about how to store this data. External data files could be parsed by a level class, and certain objects can be spawned through that. I could also create a base level class and extend it for each level, but that'd create a large amount of classes. Another idea is to have one level parser class, but have a case for each level. This would be extremely silly and bulky, but I mention it because I found that I did this at 2 AM last night. I'm finally getting why I have to plan out my inheritances, though. RIP project. I might be completely missing another option.

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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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• The purpose of using invert and transpose

  - by user699215

  In openGl ES and the World of 3D - why use the invers matrix? The thing is that I dont have any intuition to, why it is used, therefore please correct me: As fare as I understand, it is used in shaders - and can help you to figure out the opposite direction of the normals? Invers in ordinary numbers is like; The product of a number and its multiplicative inverse is 1. Observe that 3/5 * 5/3 = 1. In a matrix this will give you the Identity Matrix, which is the base coordinate system or the orion of the World space - right. But the invers is - some other coordinate system? You can use the transpose(Row-major order to Column-major order) of a square matrix to find the inverted matrix, as calculating the invers is process heavy - and the transpose is giving you the inverted matrix as a bi product? Again, I am looking for getting some intuition of this - and therefore be able to use it as intended. Thank you for any reply that will guide me in the right direction. Regards

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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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• How to make Pokémon White 3D effect?

  - by Pipo

  I just wondered how to create a 3D effect similar to Pokemon White/Black? It seems to be not polygon based, but created just with sprites. If the perspective changes the sprites stay sharp and don't get blurred. How can I archive this? Source: https://www.youtube.com/watch?v=fZEPUPYOnRc&feature=youtube_gdata_player Edit: Wow, two downvotes because I used a video instead of screenshots? Don't get me wrong, I thank you, because you want to help me, but the 3D effect can be better understand in motion. Anyway, here is a screenshot: http://wearearcade.com/wp-content/uploads/2011/03/pokemon-black-white-starter-town.jpg So, if this is a hardware limitation, how can I archive this o na different hardware, e.g. a HTML5 game? Thank you.

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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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• Behaviour tree code example?

  - by jokoon

  http://altdevblogaday.org/2011/02/24/introduction-to-behavior-trees/ Obviously the most interesting article I found on this website. What do you think about it ? It lacks some code example, don't you know any ? I also read that state machines are not very flexible compared to behaviour trees... On top of that I'm not sure if there is a true link between state machines and the state pattern... is there ?

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• 2D Animation Smoothness - Delta time vs. Kinematics

  - by viperld002

  I'm animating a sprite in 2D with key frames of rotation and xy-positions. I've recently had a discussion with someone saying that when the device (happens to be an iPad using cocos2D) hits a performance bump due to whatever else the user may be doing, lag will arise and that the best way to fight it is to not use actual positions, but velocities, accelerations and torques with kinematics. His message is to evaluate the positions and rotations from these speeds at the current point in time. I've never experienced a situation where I've heard of using kinematics to stem lag in 2D animations and am not sure of how effective it could be. Also, it seems to be overkill. The application is not networked so it's all running on a local device. The desired effect is that the animation always plays as closely as it can to the target frame rate. Wouldn't the technique suffer the same problems as just using the time since the last frame or a fixed time step since the kinematics would also require some time value to perform the calculation? What techniques could you suggest to best achieve the desired effect? EDIT 1 Thank you for your responses, they are very illuminating. I want to clarify my question before choosing an answer however, to make sure that this post really serves it's purpose. I have a sprite of a ball, and a text file with 3 arrays worth of information (rotation,translations x, translations y) with each unit of information existing as a key frame to be stepped through (0 to 49 and back to 0 to replay it again). I have this playing by interpolating from the current key frame to the next, every n-units of time. The animation is visibly correct when compared to a video I was given of it, and it is smooth because of the interpolations between the key frames. This is the existing state of the project. There are no physics simulated, only a static animation of a ball moving in a way an artist specifically designed. Should I, instead of rotation in degrees and translations by positions in space, derive velocities, accelerations and torques to express this static animation as a function of time? As in, position now = foo(time now), where foo uses kinematics.

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• what's wrong with this Lua code (creating text inside listener in Corona)

  - by Greg

  If you double/triple click on the myObject here the text does NOT disappear. Why is this not working when there are multiple events being fired? That is, are there actually multiple "text" objects, with some existing but no longer having a reference to them held by the local "myText" variable? Do I have to manually removeSelf() on the local "myText" field before assigning it another "display.newText(...)"? display.setStatusBar( display.HiddenStatusBar ) local myText local function hideMyText(event) print ("hideMyText") myText.isVisible = false end local function showTextListener(event) if event.phase == "began" then print("showTextListener") myText = display.newText("Hello World!", 0, 0, native.systemFont, 30) timer.performWithDelay(1000, hideMyText, 1 ) end end -- Display object to press to show text local myObject = display.newImage( "inventory_button.png", display.contentWidth/2, display.contentHeight/2) myObject:addEventListener("touch", showTextListener) Question 2 - Also why is it the case that if I add a line BEFORE "myText = ..." of: a) "if myText then myText:removeSelf() end" = THIS FIXES THINGS, whereas b) "if myText then myText=nil end" = DOES NOT FIX THINGS Interested in hearing how Lua works here re the answer...

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• Programming bots in games

  - by Bane

  I'm interested in how bots are usually written. Here's my situation: I plan to make an online 2D mecha game in HTML5, and the server-side will be done with node. It is intended to be multiplayer, but I also want to make bots in case there aren't enough players. How does my game logic see them, as players or as bots? Is there a standard by which I should make them? Also, any general tips and hints will be OK.

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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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• 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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• What should I worry about when changing OpenGL origin to upper left of screen?

  - by derivative

  For self education, I'm writing a 2D platformer engine in C++ using SDL / OpenGL. I initially began with pure SDL using the tutorials on sdltutorials.com and lazyfoo.net, but I'm now rendering in an OpenGL context (specifically immediate mode but I'm learning about VAOs/VBOs) and using SDL for interface, audio, etc. SDL uses a coordinate system with the origin in the upper left of the screen and the positive y-axis pointing down. It's easy to set up my orthographic projection in OpenGL to mirror this. I know that texture coordinates are a right-hand system with values from 0 to 1 -- flipping the texture vertically before rendering (well, flip the file before loading) yields textures that render correctly... which is fine if I'm drawing the entire texture, but ultimately I'll be using tilesets and can imagine problems. What should I be concerned about in terms of rendering when I do this? If anybody has any advice or they've done this themselves and can point out future pitfalls, that would be great, but really any thoughts would be appreciated.

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