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  • Annoying flickering of vertices and edges (possible z-fighting)

    - by Belgin
    I'm trying to make a software z-buffer implementation, however, after I generate the z-buffer and proceed with the vertex culling, I get pretty severe discrepancies between the vertex depth and the depth of the buffer at their projected coordinates on the screen (i.e. zbuffer[v.xp][v.yp] != v.z, where xp and yp are the projected x and y coordinates of the vertex v), sometimes by a small fraction of a unit and sometimes by 2 or 3 units. Here's what I think is happening: Each triangle's data structure holds the plane's (that is defined by the triangle) coefficients (a, b, c, d) computed from its three vertices from their normal: void computeNormal(Vertex *v1, Vertex *v2, Vertex *v3, double *a, double *b, double *c) { double a1 = v1 -> x - v2 -> x; double a2 = v1 -> y - v2 -> y; double a3 = v1 -> z - v2 -> z; double b1 = v3 -> x - v2 -> x; double b2 = v3 -> y - v2 -> y; double b3 = v3 -> z - v2 -> z; *a = a2*b3 - a3*b2; *b = -(a1*b3 - a3*b1); *c = a1*b2 - a2*b1; } void computePlane(Poly *p) { double x = p -> verts[0] -> x; double y = p -> verts[0] -> y; double z = p -> verts[0] -> z; computeNormal(p -> verts[0], p -> verts[1], p -> verts[2], &p -> a, &p -> b, &p -> c); p -> d = p -> a * x + p -> b * y + p -> c * z; } The z-buffer just holds the smallest depth at the respective xy coordinate by somewhat casting rays to the polygon (I haven't quite got interpolation right yet so I'm using this slower method until I do) and determining the z coordinate from the reversed perspective projection formulas (which I got from here: double z = -(b*Ez*y + a*Ez*x - d*Ez)/(b*y + a*x + c*Ez - b*Ey - a*Ex); Where x and y are the pixel's coordinates on the screen; a, b, c, and d are the planes coefficients; Ex, Ey, and Ez are the eye's (camera's) coordinates. This last formula does not accurately give the exact vertices' z coordinate at their projected x and y coordinates on the screen, probably because of some floating point inaccuracy (i.e. I've seen it return something like 3.001 when the vertex's z-coordinate was actually 2.998). Here is the portion of code that hides the vertices that shouldn't be visible: for(i = 0; i < shape.nverts; ++i) { double dist = shape.verts[i].z; if(z_buffer[shape.verts[i].yp][shape.verts[i].xp].z < dist) shape.verts[i].visible = 0; else shape.verts[i].visible = 1; } How do I solve this issue? EDIT I've implemented the near and far planes of the frustum, with 24 bit accuracy, and now I have some questions: Is this what I have to do this in order to resolve the flickering? When I compare the z value of the vertex with the z value in the buffer, do I have to convert the z value of the vertex to z' using the formula, or do I convert the value in the buffer back to the original z, and how do I do that? What are some decent values for near and far? Thanks in advance.

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  • Beginner question about vertex arrays in OpenGL

    - by MrDatabase
    Is there a special order in which vertices are entered into a vertex array? Currently I'm drawing single textures like this: glBindTexture(GL_TEXTURE_2D, texName); glVertexPointer(2, GL_FLOAT, 0, vertices); glTexCoordPointer(2, GL_FLOAT, 0, coordinates); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); where vertices has four "xy pairs". This is working fine. As a test I doubled the sizes of the vertices and coordinates arrays and changed the last line above to: glDrawArrays(GL_TRIANGLE_STRIP, 0, 8); since vertices now contains eight "xy pairs". I do see two textures (the second is intentionally offset from the first). However the textures are now distorted. I've tried passing GL_TRIANGLES to glDrawArrays instead of GL_TRIANGLE_STRIP but this doesn't work either. I'm so new to OpenGL that I thought it's best to just ask here :-) Cheers!

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  • Basic game architechture best practices in Cocos2D on iOS

    - by MrDatabase
    Consider the following simple game: 20 squares floating around an iPhone's screen. Tapping a square causes that square to disappear. What's the "best practices" way to set this up in Cocos2D? Here's my plan so far: One Objective-c GameState singleton class (maintains list of active squares) One CCScene (since there's no menus etc) One CCLayer (child node of the scene) Many CCSprite nodes (one for each square, all child nodes of the layer) Each sprite listens for a tap on itself. Receive tap = remove from GameState Since I'm relatively new to Cocos2D I'd like some feedback on this design. For example I'm unsure of the GameState singleton. Perhaps it's unnecessary.

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  • Shadowmap first phase and shaders

    - by KaiserJohaan
    I am using OpenGL 3.3 and am tryin to implement shadow mapping using cube maps. I have a framebuffer with a depth attachment and a cube map texture. My question is how to design the shaders for the first pass, when creating the shadowmap. This is my vertex shader: in vec3 position; uniform mat4 lightWVP; void main() { gl_Position = lightWVP * vec4(position, 1.0); } Now, do I even need a fragment shader in this shader pass? from what I understand after reading http://www.opengl.org/wiki/Fragment_Shader, by default gl_FragCoord.z is written to the currently attached depth component (to which my cubemap texture is bound to). Thus I shouldnt even need a fragment shader for this pass and from what I understand, there is no other work to do in the fragment shader other than writing this value. Is this correct?

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  • Character jump animation is not working when i hit the space bar

    - by muzzy
    i am having an issue with my game in XNA. My jump sprite sheet for my character does not trigger when i hit the space bar. I cant seem to find the problem. Please help me. I am also put the code below to make things easier. namespace WindowsGame4 { public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; // start of new code Texture2D playerWalk; // sprite sheet of walk cycle (14 frames) Texture2D idle; // idle animation Texture2D jump; // jump animation Vector2 playerPos; // to hold x and y position info for the player Point frameDimensions; // to hold width and height values for the frames int presentFrame; // to record which frame we are on at any given time int noOfFrames; // to hold the total number of frames in the spritesheet int elapsedTime; // to know how long each frame has been shown int frameDuration; // to hold info about how long each frame should be shown SpriteEffects flipDirection; // SpriteEffects object int speed; //rate of movement int upMovement; int downMovement; int rightMovement; int leftMovement; int jumpApex; string state; //this is going to be "idle","walking" or "jumping". KeyboardState previousKeyboardState; Vector2 originalPlayerPos; Vector2 movementDirection; Vector2 movementSpeed; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } protected override void Initialize() { // textures will be defined in the LoadContent() method playerPos = new Vector2(0, 200); // starting position for the player is at the left of the screen, and a Y position of 200 frameDimensions = new Point(55, 65); // each frame in the idle sprite sheet is 55 wide by 65 high presentFrame = 0; // start at frame 0 noOfFrames = 5; // there are 5 frames in the idle cycle elapsedTime = 0; // set elapsed time to start at 0 frameDuration = 80; // 80 milliseconds is how long each frame will show for (the higher the number, the slower the animation) flipDirection = SpriteEffects.None; // set the value of flipDirection to none speed = 200; upMovement = -2; downMovement = 2; rightMovement = 1; leftMovement = -1; jumpApex = 100; state = "idle"; previousKeyboardState = Keyboard.GetState(); originalPlayerPos = Vector2.Zero; movementDirection = Vector2.Zero; movementSpeed = Vector2.Zero; base.Initialize(); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); playerWalk = Content.Load<Texture2D>("sprites/walkSmall"); // load the walk cycle spritesheet idle = Content.Load<Texture2D>("sprites/idleCycle"); // load the idle cycle sprite sheet jump = Content.Load<Texture2D>("sprites/jump"); // load the jump cycle sprite sheet } protected override void UnloadContent() // we're not using this method at the moment { } protected override void Update(GameTime gameTime) // Update method - used it to call a number of other methods { if (Keyboard.GetState().IsKeyDown(Keys.Escape)) { this.Exit(); // Exit the game if the Escape key is pressed } KeyboardState presentKeyboardState = Keyboard.GetState(); UpdateMovement(presentKeyboardState, gameTime); UpdateIdle(presentKeyboardState, gameTime); UpdateJump(presentKeyboardState); UpdateAnimation(gameTime); playerPos += movementDirection * movementSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds; previousKeyboardState = presentKeyboardState; base.Update(gameTime); } private void UpdateAnimation(GameTime gameTime) { elapsedTime += gameTime.ElapsedGameTime.Milliseconds; if (elapsedTime > frameDuration) { elapsedTime -= frameDuration; elapsedTime = elapsedTime - frameDuration; presentFrame++; if (presentFrame > noOfFrames) if (state != "jumping") { presentFrame = 0; } else { presentFrame = 8; } } } protected void UpdateMovement(KeyboardState presentKeyboardState, GameTime gameTime) { if (state == "idle") { movementSpeed = Vector2.Zero; movementDirection = Vector2.Zero; if (presentKeyboardState.IsKeyDown(Keys.Left)) { state = "walking"; movementSpeed.X = speed; movementDirection.X = leftMovement; flipDirection = SpriteEffects.FlipHorizontally; } if (presentKeyboardState.IsKeyDown(Keys.Right)) { state = "walking"; movementSpeed.X = speed; movementDirection.X = rightMovement; flipDirection = SpriteEffects.None; } } } private void UpdateIdle(KeyboardState presentKeyboardState, GameTime gameTime) { if ((presentKeyboardState.IsKeyUp(Keys.Left) && previousKeyboardState.IsKeyDown(Keys.Left) || presentKeyboardState.IsKeyUp(Keys.Right) && previousKeyboardState.IsKeyDown(Keys.Right) && state != "jumping")) { state = "idle"; } } private void UpdateJump(KeyboardState presentKeyboardState) { if (state == "walking" || state == "idle") { if (presentKeyboardState.IsKeyDown(Keys.Space) && !presentKeyboardState.IsKeyDown(Keys.Space)) { presentFrame = 1; DoJump(); } } if (state == "jumping") { if (originalPlayerPos.Y - playerPos.Y > jumpApex) { movementDirection.Y = downMovement; } if (playerPos.Y > originalPlayerPos.Y) { playerPos.Y = originalPlayerPos.Y; state = "idle"; movementDirection = Vector2.Zero; } } } private void DoJump() { if (state != "jumping") { state = "jumping"; originalPlayerPos = playerPos; movementDirection.Y = upMovement; movementSpeed = new Vector2(speed, speed); } } protected override void Draw(GameTime gameTime) // Draw method { GraphicsDevice.Clear(Color.CornflowerBlue); spriteBatch.Begin(); // begin the spritebatch if (state == "walking") { noOfFrames = 14; frameDimensions = new Point(55, 65); Vector2 playerWalkPos = new Vector2(playerPos.X, playerPos.Y - 28); spriteBatch.Draw(playerWalk, playerWalkPos, new Rectangle((presentFrame * frameDimensions.X), 0, frameDimensions.X, frameDimensions.Y), Color.White, 0, Vector2.Zero, 1, flipDirection, 0); } if (state == "idle") { noOfFrames = 5; frameDimensions = new Point(55, 65); Vector2 idlePos = new Vector2(playerPos.X, playerPos.Y - 28); spriteBatch.Draw(idle, idlePos, new Rectangle((presentFrame * frameDimensions.X), 0, frameDimensions.X, frameDimensions.Y), Color.White, 0, Vector2.Zero, 1, flipDirection, 0); } if (state == "jumping") { noOfFrames = 9; frameDimensions = new Point(55, 92); Vector2 jumpPos = new Vector2(playerPos.X, playerPos.Y - 28); spriteBatch.Draw(jump, jumpPos, new Rectangle((presentFrame * frameDimensions.X), 0, frameDimensions.X, frameDimensions.Y), Color.White, 0, Vector2.Zero, 1, flipDirection, 0); } spriteBatch.End(); // end the spritebatch commands base.Draw(gameTime); } } }

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  • How to implement explosion in OpenGL?

    - by Chan
    I'm relatively new to OpenGL and I'm clueless how to implement explosion. So could anyone give me some ideas how to start? Suppose the explosion occurs at location $(x, y, z)$, then I'm thinking of randomly generate a collection of vectors with $(x, y, z)$ as origin, then draw some particle (glutSolidCube) which move along this vector for some period of time, says after 1000 updates, it disappear. Is this approach feasible? A minimal example would be greatly appreciated.

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  • Would someone please explain Octree Collisions to me?

    - by A-Type
    I've been reading everything I can find on the subject and I feel like the pieces are just about to fall into place, but I just can't quite get it. I'm making a space game, where collisions will occur between planets, ships, asteroids, and the sun. Each of these objects can be subdivided into 'chunks', which I have implemented to speed up rendering (the vertices can and will change often at runtime, so I've separated the buffers). These subdivisions also have bounding primitives to test for collision. All of these objects are made of blocks (yeah, it's that kind of game). Blocks can also be tested for rough collisions, though they do not have individual bounding primitives for memory reasons. I think the rough testing seems to be sufficient, though. So, collision needs to be fairly precise; at block resolution. Some functions rely on two blocks colliding. And, of course, attacking specific blocks is important. Now what I am struggling with is filtering my collision pairs. As I said, I've read a lot about Octrees, but I'm having trouble applying it to my situation as many tutorials are vague with very little code. My main issues are: Are Octrees recalculated each frame, or are they stored in memory and objects are shuffled into different divisions as they move? Despite all my reading I still am not clear on this... the vagueness of it all has been frustrating. How far do Octrees subdivide? Planets in my game are quite large, while asteroids are smaller. Do I subdivide to the size of the planet, or asteroid (where planet is in multiple divisions)? Or is the limit something else entirely, like number of elements in the division? Should I load objects into the octrees as 'chunks' or in the whole, then break into chunks later? This could be specific to my implementation, I suppose. I was going to ask about how big my root needed to be, but I did manage to find this question, and the second answer seems sufficient for me. I'm afraid I don't really get what he means by adding new nodes and doing subdivisions upon adding new objects, probably because I'm confused about whether the tree is maintained in memory or recalculated per-frame.

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  • Rotating wheel with touch adding velocity

    - by Lewis
    I have a wheel control in a game which is setup like so: - (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:[touch view]]; location = [[CCDirector sharedDirector] convertToGL:location]; if (CGRectContainsPoint(wheel.boundingBox, location)) { CGPoint firstLocation = [touch previousLocationInView:[touch view]]; CGPoint location = [touch locationInView:[touch view]]; CGPoint touchingPoint = [[CCDirector sharedDirector] convertToGL:location]; CGPoint firstTouchingPoint = [[CCDirector sharedDirector] convertToGL:firstLocation]; CGPoint firstVector = ccpSub(firstTouchingPoint, wheel.position); CGFloat firstRotateAngle = -ccpToAngle(firstVector); CGFloat previousTouch = CC_RADIANS_TO_DEGREES(firstRotateAngle); CGPoint vector = ccpSub(touchingPoint, wheel.position); CGFloat rotateAngle = -ccpToAngle(vector); CGFloat currentTouch = CC_RADIANS_TO_DEGREES(rotateAngle); wheelRotation += (currentTouch - previousTouch) * 0.6; //limit speed 0.6 } } I update the rotation of a the wheel in the update method by doing: wheel.rotation = wheelRotation; Now once the user lets go of the wheel I want it to rotate back to where it was before but not without taking into account the velocity of the swipe the user has done. This is the bit I really can't get my head around. So if the swipe generates a lot of velocity then the wheel will carry on moving slightly in that direction until the overall force which pulls the wheel back to the starting position kicks in. Any ideas/code snippets?

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  • (Abstract) Game engine design

    - by lukeluke
    I am writing a simple 2D game (for mobile platforms) for the first time. From an abstract point of view, i have the main player controlled by the human, the enemies, elments that will interact with the main player, other living elements that will be controlled by a simple AI (both enemies and non-enemies). The human player will be totally controlled by the player, the other actors will be controlled by AI. So i have a class CActor and a class CActorLogic to start with. I would define a CActor subclass CHero (the main player controlled with some input device). This class will probably implement some type of listener, in order to capture input events. The other players controlled by the AI will be probably a specific subclass of CActor (a subclass per-type, obviously). This seems to be reasonable. The CActor class should have a reference to a method of CActorLogic, that we will call something like CActorLogic::Advance() or similar. Actors should have a visual representation. I would introduce a CActorRepresentation class, with a method like Render() that will draw the actor (that is, the right frame of the right animation). Where to change the animation? Well, the actor logic method Advance() should take care of checking collisions and other things. I would like to discuss the design of a game engine (actors, entities, objects, messages, input handling, visualization of object states (that is, rendering, sound output and so on)) but not from a low level point of view, but from an high level point of view, like i have described above. My question is: is there any book/on line resource that will help me organize things (using an object oriented approach)? Thanks

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  • How do I draw video frames onto the screen permanently using XNA?

    - by izb
    I have an app that plays back a video and draws the video onto the screen at a moving position. When I run the app, the video moves around the screen as it plays. Here is my Draw method... protected override void Draw(GameTime gameTime) { Texture2D videoTexture = null; if (player.State != MediaState.Stopped) videoTexture = player.GetTexture(); if (videoTexture != null) { spriteBatch.Begin(); spriteBatch.Draw( videoTexture, new Rectangle(x++, 0, 400, 300), /* Where X is a class member */ Color.White); spriteBatch.End(); } base.Draw(gameTime); } The video moves horizontally acros the screen. This is not exactly as I expected since I have no lines of code that clear the screen. My question is why does it not leave a trail behind? Also, how would I make it leave a trail behind?

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  • Material, Pass, Technique and shaders

    - by Papi75
    I'm trying to make a clean and advanced Material class for the rendering of my game, here is my architecture: class Material { void sendToShader() { program->sendUniform( nameInShader, valueInMaterialOrOther ); } private: Blend blendmode; ///< Alpha, Add, Multiply, … Color ambient; Color diffuse; Color specular; DrawingMode drawingMode; // Line Triangles, … Program* program; std::map<string, TexturePacket> textures; // List of textures with TexturePacket = { Texture*, vec2 offset, vec2 scale} }; How can I handle the link between the Shader and the Material? (sendToShader method) If the user want to send additionals informations to the shader (like time elapsed), how can I allow that? (User can't edit Material class) Thanks!

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  • Collision and Graphics integration

    - by Shlomi Atia
    I'm a little confused about the integration between collision and graphics. They both need to share the same position in the world. The most obvious choice is the center of the entity, which is good for bounding volumes and fixed sized sprites. However, for characters with variable height size sprites like this: http://gamemedia.wcgame.ru/data/2011-07-17/game-sprite-sheet.jpg This is no longer good. The character won't align to the ground if I'll draw it from the center. I can just make the sprites the same height, but it will be a waste of memory (the largest sprite is 4 times larger then the smallest one). Even then, this is not an option at all with skeletal sprites like this one: http://user-generated-content.java-gaming.org/img-vault/212a171fc1ebb27ab77608fb9b2dd9bd9205361ce6300b21a7f8d06d025fbbd8.png It seems that the graphics need to be drawn from the ground for characters, but not for other images such as scenery and obstacles. The only solution I could think of was having another position called draw-position, which is the entity center for images, and is the the bottom of the collision volume for characters. Then when I draw relative to that position, it should work properly. I haven't found any references for something like that, so I'm kinda insecure about it. Does anyone knows of a better approach for this problem? Thanks

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  • Exporting .jar files with Jarsplice

    - by SystemNetworks
    Help! I'm Using Mac OS X 10.8 Mountain Lion and Using Eclipse. I'm using the library called Slick and Lwjgl. When i first exported it, it has a .jar file. I followed some You Tube Tutorials (Different, they don't have slick) It worked for them. I don't know why it dosen't work for me. Should i put Slick-util too? I didn't even use lwjgl btw. Please help!!! Jars I used(Libraries) Slick LWJGL(I didn't use it) Tutorials I followed TheCodingUniverse(Exporting) TheNewBoston(The Code and Set-up) Programs I used Eclipse IDE Java Jarsplice No warnings found or errors. It is perfect! But Nothing shows up in the screen everytime I pressed the jar(After Jarsplice) Help!!!

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  • How stoper one annimation model on XNA?

    - by Mehdi Bugnard
    I met a Difficulty for one stoper annimation. Everything works great starter for the animation. But I do not see how stoper and can continue the annimation paused. The "animationPlayer.StartClip (clip)" is used to choke the annimation but impossible to find a way to stoper Thans's a lot Here is my code to use. protected override void LoadContent() { //Model - Player model_player = Content.Load<Model>("Models\\Player\\models"); // Look up our custom skinning information. SkinningData skinningData = model_player.Tag as SkinningData; if (skinningData == null) throw new InvalidOperationException ("This model does not contain a SkinningData tag."); // Create an animation player, and start decoding an animation clip. animationPlayer = new AnimationPlayer(skinningData); AnimationClip clip = skinningData.AnimationClips["ArmLowAction_006"]; animationPlayer.StartClip(clip); } protected overide update(GameTime gameTime) { KeyboardState key = Keyboard.GetState(); // If player don't move -> stop anim if (!key.IsKeyDown(Keys.W) && !keyStateOld.IsKeyUp(Keys.S) && !keyStateOld.IsKeyUp(Keys.A) && !keyStateOld.IsKeyUp(Keys.D)) { //animation stop ? not exist ? animationPlayer.Stop(); isPlayerStop = true; } else { if(isPlayerStop == true) { isPlayerStop = false; animationPlayer.StartClip(Clip); } }

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  • Inverse projection: question about w coordinate

    - by fayeWilly
    I have to perform in shader an inverse projection from a u/v of a render target. What I do is: Get NDC as 2*(u,v,depth) - 1 Then world space as tmp = (P*V)^-1 * (NDC,1.0); world space = tmp/tmp.w; This apparently works, but I am confused about the w division there. Why this work? Shouldn't be a multiplication by a w somewhere (as in the "forward" pipeline there is the perpsective division?) Thank you, Faye

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  • how to transform child elements position into a world position

    - by MrGreg
    So Im making a 2d space game and I have a bunch of spaceships that have turrets. Objects have a position and orientation, the ships being in world coordinates while the turrets are children and coordinates are relative to their parents. How do I efficiently calculate the position of a turret in world coordinates (i.e. when it fires and I need to know where to place a bullet in the world)? Calculating the turrets orientation is trivial - I just add the turrets relative angle to its parents. For position though, I guess I could do a bunch of trigonometry but this MUST be a common problem with a good/fast general solution? Should I be relearning how to do matrix math again? :) btw - Im creating the game in javascript+canvas but its the math/algorithm im interested in here Cheers, Greg

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  • Can I use PBOs for textures in iOS?

    - by Radu
    As far as I can see, there is no GL_PIXEL_UNPACK_BUFFER. Also, the OpenGL ES 2.0 specification (and as far as I know, no iOS device currently supports OpenGL ES 2.0) states that glMapBufferOES() can only use GL_ARRAY_BUFFER as a target, yet glTexImage2D() and glTexSubImage2D() only seem to use PBOs if GL_PIXEL_UNPACK_BUFFER is bound. The OpenGL documentation for glBindBuffer() also states that: GL_PIXEL_PACK_BUFFER and GL_PIXEL_UNPACK_BUFFER are available only if the GL version is 2.1 or greater. So, can I use PBOs for textures? Am I missing something obvious?

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  • How to move a line of sprites in a sine wave?

    - by electroflame
    So, I'm spawning a horizontal line of enemies that I would like to have move in a nice wave. Currently I tried: Enemy.position.X += Enemy.velocity.X; Enemy.position.Y += -(float)Math.Cos(Enemy.position.X / 200) * 5; This...kind of works. But the wave is not a true wave. The top and bottom of one pass are not the same (e.g. 5 for the top, and -5 for the bottom (I don't mean literal points, I just meant that it's not symmetrical)). Is there a better way to do this? I would like the whole line to move in a wave, so it looks fluid. By that, I mean that it should look like each enemy is "following" the one in front of it. The code I posted does have this fluidity to it, but like I said, it's not a perfect wave. Any ideas? Thanks in advance.

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  • Creating smooth lighting transitions using tiles in HTML5/JavaScript game

    - by user12098
    I am trying to implement a lighting effect in an HTML5/JavaScript game using tile replacement. What I have now is kind of working, but the transitions do not look smooth/natural enough as the light source moves around. Here's where I am now: Right now I have a background map that has a light/shadow spectrum PNG tilesheet applied to it - going from darkest tile to completely transparent. By default the darkest tile is drawn across the entire level on launch, covering all other layers etc. I am using my predetermined tile sizes (40 x 40px) to calculate the position of each tile and store its x and y coordinates in an array. I am then spawning a transparent 40 x 40px "grid block" entity at each position in the array The engine I'm using (ImpactJS) then allows me to calculate the distance from my light source entity to every instance of this grid block entity. I can then replace the tile underneath each of those grid block tiles with a tile of the appropriate transparency. Currently I'm doing the calculation like this in each instance of the grid block entity that is spawned on the map: var dist = this.distanceTo( ig.game.player ); var percentage = 100 * dist / 960; if (percentage < 2) { // Spawns tile 64 of the shadow spectrum tilesheet at the specified position ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 64 ); } else if (percentage < 4) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 63 ); } else if (percentage < 6) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 62 ); } // etc... (sorry about the weird spacing, I still haven't gotten the hang of pasting code in here properly) The problem is that like I said, this type of calculation does not make the light source look very natural. Tile switching looks too sharp whereas ideally they would fade in and out smoothly using the spectrum tilesheet (I copied the tilesheet from another game that manages to do this, so I know it's not a problem with the tile shades. I'm just not sure how the other game is doing it). I'm thinking that perhaps my method of using percentages to switch out tiles could be replaced with a better/more dynamic proximity forumla of some sort that would allow for smoother transitions? Might anyone have any ideas for what I can do to improve the visuals here, or a better way of calculating proximity with the information I'm collecting about each tile? (PS: I'm reposting this from Stack Overflow at someone's suggestion, sorry about the duplicate!)

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  • Numerically stable(ish) method of getting Y-intercept of mouse position?

    - by Fraser
    I'm trying to unproject the mouse position to get the position on the X-Z plane of a ray cast from the mouse. The camera is fully controllable by the user. Right now, the algorithm I'm using is... Unproject the mouse into the camera to get the ray: Vector3 p1 = Vector3.Unproject(new Vector3(x, y, 0), 0, 0, width, height, nearPlane, farPlane, viewProj; Vector3 p2 = Vector3.Unproject(new Vector3(x, y, 1), 0, 0, width, height, nearPlane, farPlane, viewProj); Vector3 dir = p2 - p1; dir.Normalize(); Ray ray = Ray(p1, dir); Then get the Y-intercept by using algebra: float t = -ray.Position.Y / ray.Direction.Y; Vector3 p = ray.Position + t * ray.Direction; The problem is that the projected position is "jumpy". As I make small adjustments to the mouse position, the projected point moves in strange ways. For example, if I move the mouse one pixel up, it will sometimes move the projected position down, but when I move it a second pixel, the project position will jump back to the mouse's location. The projected location is always close to where it should be, but it does not smoothly follow a moving mouse. The problem intensifies as I zoom the camera out. I believe the problem is caused by numeric instability. I can make minor improvements to this by doing some computations at double precision, and possibly abusing the fact that floating point calculations are done at 80-bit precision on x86, however before I start micro-optimizing this and getting deep into how the CLR handles floating point, I was wondering if there's an algorithmic change I can do to improve this? EDIT: A little snooping around in .NET Reflector on SlimDX.dll: public static Vector3 Unproject(Vector3 vector, float x, float y, float width, float height, float minZ, float maxZ, Matrix worldViewProjection) { Vector3 coordinate = new Vector3(); Matrix result = new Matrix(); Matrix.Invert(ref worldViewProjection, out result); coordinate.X = (float) ((((vector.X - x) / ((double) width)) * 2.0) - 1.0); coordinate.Y = (float) -((((vector.Y - y) / ((double) height)) * 2.0) - 1.0); coordinate.Z = (vector.Z - minZ) / (maxZ - minZ); TransformCoordinate(ref coordinate, ref result, out coordinate); return coordinate; } // ... public static void TransformCoordinate(ref Vector3 coordinate, ref Matrix transformation, out Vector3 result) { Vector3 vector; Vector4 vector2 = new Vector4 { X = (((coordinate.Y * transformation.M21) + (coordinate.X * transformation.M11)) + (coordinate.Z * transformation.M31)) + transformation.M41, Y = (((coordinate.Y * transformation.M22) + (coordinate.X * transformation.M12)) + (coordinate.Z * transformation.M32)) + transformation.M42, Z = (((coordinate.Y * transformation.M23) + (coordinate.X * transformation.M13)) + (coordinate.Z * transformation.M33)) + transformation.M43 }; float num = (float) (1.0 / ((((transformation.M24 * coordinate.Y) + (transformation.M14 * coordinate.X)) + (coordinate.Z * transformation.M34)) + transformation.M44)); vector2.W = num; vector.X = vector2.X * num; vector.Y = vector2.Y * num; vector.Z = vector2.Z * num; result = vector; } ...which seems to be a pretty standard method of unprojecting a point from a projection matrix, however this serves to introduce another point of possible instability. Still, I'd like to stick with the SlimDX Unproject routine rather than writing my own unless it's really necessary.

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  • Velocity collision detection (2D)

    - by ultifinitus
    Alright, so I have made a simple game engine (see youtube) And my current implementation of collision resolution has a slight problem, involving the velocity of a platform. Basically I run through all of the objects necessary to detect collisions on and resolve those collisions as I find them. Part of that resolution is setting the player's velocity = the platform's velocity. Which works great! Unless I have a row of platforms moving at different velocities or a platform between a stack of tiles.... (current system) bool player::handle_collisions() { collisions tcol; bool did_handle = false; bool thisObjectHandle = false; for (int temp = 0; temp < collideQueue.size(); temp++) { thisObjectHandle = false; tcol = get_collision(prevPos.x,y,get_img()->get_width(),get_img()->get_height(), collideQueue[temp]->get_position().x,collideQueue[temp]->get_position().y, collideQueue[temp]->get_img()->get_width(),collideQueue[temp]->get_img()->get_height()); if (prevPos.y >= collideQueue[temp]->get_prev_pos().y + collideQueue[temp]->get_img()->get_height()) if (tcol.top > 0) { add_pos(0,tcol.top); set_vel(get_vel().x,collideQueue[temp]->get_vel().y); thisObjectHandle = did_handle = true; } if (prevPos.y + get_img()->get_height() <= collideQueue[temp]->get_prev_pos().y) if (tcol.bottom > 0) { add_pos(collideQueue[temp]->get_vel().x,-tcol.bottom); set_vel(get_vel().x/*collideQueue[temp]->get_vel().x*/,collideQueue[temp]->get_vel().y); ableToJump = true; jumpTimes = maxjumpable; thisObjectHandle = did_handle = true; } /// /// ADD CODE FROM NEXT CODE BLOCK HERE (on forum, not in code) /// } for (int temp = 0; temp < collideQueue.size(); temp++) { thisObjectHandle = false; tcol = get_collision(x,y,get_img()->get_width(),get_img()->get_height(), collideQueue[temp]->get_position().x,collideQueue[temp]->get_position().y, collideQueue[temp]->get_img()->get_width(),collideQueue[temp]->get_img()->get_height()); if (prevPos.x + get_img()->get_width() <= collideQueue[temp]->get_prev_pos().x) if (tcol.left > 0) { add_pos(-tcol.left,0); set_vel(collideQueue[temp]->get_vel().x,get_vel().y); thisObjectHandle = did_handle = true; } if (prevPos.x >= collideQueue[temp]->get_prev_pos().x + collideQueue[temp]->get_img()->get_width()) if (tcol.right > 0) { add_pos(tcol.right,0); set_vel(collideQueue[temp]->get_vel().x,get_vel().y); thisObjectHandle = did_handle = true; } } return did_handle; } (if I add the following code {where the comment to do so is}, which is glitchy, the above problem doesn't happen, though it brings others) if (!thisObjectHandle) { if (tcol.bottom > tcol.top) { add_pos(collideQueue[temp]->get_vel().x,-tcol.bottom); set_vel(get_vel().x,collideQueue[temp]->get_vel().y); } else if (tcol.top > tcol.bottom) { add_pos(0,tcol.top); set_vel(get_vel().x,collideQueue[temp]->get_vel().y); } } How would you change my system to prevent this?

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  • Variables in static library are never initialized. Why?

    - by Coyote
    I have a bunch of variables that should be initialized then my game launches, but must of them are never initialized. Here is an example of the code: MyClass.h class MyClass : public BaseObject { DECLARE_CLASS_RTTI(MyClass, BaseObject); ... }; MyClass.cpp REGISTER_CLASS(MyClass) Where REGISTER_CLASS is a macro defined as follow #define REGISTER_CLASS(className)\ class __registryItem##className : public __registryItemBase {\ virtual className* Alloc(){ return NEW className(); }\ virtual BaseObject::RTTI& GetRTTI(){ return className::RTTI; }\ }\ \ const __registryItem##className __registeredItem##className(#className); and __registryItemBase looks like this: class __registryItemBase { __registryItemBase(const _string name):mName(name){ ClassRegistry::Register(this); } const _string mName; virtual BaseObject* Alloc() = 0; virtual BaseObject::RTTI& GetRTTI() = 0; } Now the code is similar to what I currently have and what I have works flawlessly, all the registered classes are registered to a ClassManager before main(...) is called. I'm able to instantiate and configure components from scripts and auto-register them to the right system etc... The problem arrises when I create a static library (currently for the iPhone, but I fear it will happen with android as well). In that case the code in the .cpp files is never registered. Why is the resulting code not executed when it is in the library while the same code in the program's binary is always executed? Bonus questions: For this to work in the static library, what should I do? Is there something I am missing? Do I need to pass a flag when building the lib? Should I create another structure and init all the __registeredItem##className using that structure?

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  • How do I stop stretching during window re-size in XNA?

    - by Bradley Uffner
    In my windowed mode XNA game when the user resizes the window the game stops updating the window and the last frame drawn is stretched and distorted until the user releases the mouse and the resize completes. Is there any way to have the game continue to run "normally", updating frames and redrawing the screen, during the resize event? I realize that keeping the render loop going while resizing may not be possible or recommended due do hardware managed resources getting continually created and destroyed, but is there any way to stop the ugly stretching? Ideally by leaving the existing frame unscaled in the top left, or with a black screen if that isn't possible.

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  • Actor and Sprite, who should own these properties?

    - by Gerardo Marset
    I'm writing sort of a 2D game engine for making the process of creating games easier. It has two classes, Actor and Sprite. Actor is used for interactive elements (the player, enemies, bullets, a menu, an invisible instance that controls score, etc) and Sprite is used for animated (or not) images with transparency (or not). The actor may have an assigned sprite that represents it on the screen, which may change during the game. E.g. in a top-down action game you may have an actor with a sprite of a little guy that changes when attacking, walking, and facing different directions, etc. Currently the actor has x and y properties (its coordinates in the screen), while the sprite has an index property (the number of the frame currently being shown by the sprite). Since the sprite doesn't know which actor it belongs to (or if it belongs to an actor at all), the actor must pass its x and y coordinates when drawing the sprite. Also, since a actors may reset its sprite each frame (and usually do), the sprite's index property must be passed from the old to the new sprite like so (pseudocode): function change_sprite(new_sprite) old_index = my.sprite.index my.sprite = new_sprite() my.sprite.index = old_index % my.sprite.frames end I always thought this was kind of cumbersome, but it never was a big problem. Now I decided to add support for more properties. Namely a property to draw the sprite rotated, a property to draw it flipped, it a property draw it stretched, etc. These should probably belong to the sprite and not the actor, but if they do, the actor would have to pass them from the old to the new sprite each time it changes... On the other hand, if they belonged to the actor, the actor would have to pass each property to the sprite when drawing it (since the sprite doesn't know which actor it belongs to, and it shouldn't, since sprites aren't just meant to be used by actors, really). Another option I thought of would be having an extra class that owns all these properties (plus index, x and y) and links an actor with a sprite, but that doesn't come without drawbacks. So, what should I do with all these properties? Thanks!

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  • Object-Oriented OpenGL

    - by Sullivan
    I have been using OpenGL for a while and have read a large number of tutorials. Aside from the fact that a lot of them still use the fixed pipeline, they usually throw all the initialisation, state changes and drawing in one source file. This is fine for the limited scope of a tutorial, but I’m having a hard time working out how to scale it up to a full game. How do you split your usage of OpenGL across files? Conceptually, I can see the benefits of having, say, a rendering class that purely renders stuff to screen, but how would stuff like shaders and lights work? Should I have separate classes for things like lights and shaders?

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