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  • Specifying force and angle in ApplyImpulse in box2d

    - by Deepak Mahalingam
    I need to apply an impulse on a object with a particular force and at a particular angle in Box2d. If I am right the syntax would be the following: body.GetBody().ApplyImpulse(new b2Vec2(direction, power),body.GetBody().GetWorldCenter()); The problem is my direction is in angles. I found a discussion where it was said that the way we can convert an angle into a vector would be as: new b2Vec2(Math.cos(angle*Math.PI/180),Math.sin(angle*Math.PI/180)); Now I am not sure how to combine these two. In other words, if I wish to apply a force of 30 units at an angle of 30 degrees at the center of the object, how should I do it?

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  • OpenGL ES 2.0. Sprite Sheet Animation

    - by Project Dumbo Dev
    I've found a bunch of tutorials on how to make this work on Open GL 1 & 1.1 but I can't find it for 2.0. I would work it out by loading the texture and use a matrix on the vertex shader to move through the sprite sheet. I'm looking for the most efficient way to do it. I've read that when you do the thing I'm proposing you are constantly changing the VBO's and that that is not good. Edit: Been doing some research myself. Came upon this two Updating Texture and referring to the one before PBO's. I can't use PBO's since i'm using ES version of OpenGL so I suppose the best way is to make FBO's but, what I still don't get, is if I should create a Sprite atlas/batch and make a FBO/loadtexture for each frame of if I should load every frame into the buffer and change just de texture directions.

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  • Variable number of GUI Buttons

    - by Wakaka
    I have a generic HTML5 Canvas GUI Button class and a Scene class. The Scene class has a method called createButton(), which will create a new Button with onclick parameter and store it in a list of buttons. I call createButton() for all UI buttons when initializing the Scene. Because buttons can appear and disappear very often during rendering, Scene would first deactivate all buttons (temporarily remove their onclick, onmouseover etc property) before each render frame. During rendering, the renderer would then activate the required buttons for that frame. The problem is that part of the UI requires a variable number of buttons, and their onclick, onmouseover etc properties change frequently. An example is a buffs system. The UI will list all buffs as square sprites for the current unit selected, and mousing over each square will bring up a tooltip with some information on the buff. But the number of buffs is variable thus I won't know how many buttons to create at the start. What's the best way to solve this problem? P.S. My game is in Javascript, and I know I can use HTML buttons, but would like to make my game purely Canvas-based. Create buttons on-the-fly during rendering. Thus I will only have buttons when I require them. After the render frame these buttons would be useless and removed. Create a fixed set of buttons that I'm going to assume the number of buffs per unit won't exceed. During each render frame activate the buttons accordingly and set their onmouseover property. Assign a button to each Buff instance. This sounds wrong as the buff button is a part of the GUI which can only have one unit selected. Assigning a button to every single Buff in the game seems to be overkill. Also, I would need to change the button's position every render frame since its order in the unit's list of buffs matter. Any other solutions? I'm actually quite for idea (1) but am worried about the memory/time issues of creating a new Button() object every render frame. But this is in Javascript where object creation is oh-so-common ({} mainly) due to automatic garbage collection. What is your take on this? Thanks!

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  • Physics don't apply on a unique body AndEngine

    - by Kanga
    I am developing a game in AndEngine so far I managed to create everything I wanted for my sprite that was connected to a BoxBody. I was rotating it moving it everything was great. I wanted my collision detection to be more precise so I changed from boxBody to unique irregular shaped body. I found all the vertices and I just replaced the newly created irregular shaped body with the boxbody everywhere in my code. Not only that the image of the sprite is not in place but all the physics and maths I was doing for movement and physics wont work. Please help me :(. Thanks in advance.

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  • SDL_DisplayFormat works, but not SDL_DisplayFormatAlpha

    - by Bounderby
    The following code is intended to display a green square on a black background. It executes, but the green square does not show up. However, if I change SDL_DisplayFormatAlpha to SDL_DisplayFormat the square is rendered correctly. So what don't I understand? It seems to me that I am creating *surface with an alpha mask and I am using SDL_MapRGBA to map my green color, so it would be consistent to use SDL_DisplayFormatAlpha as well. (I removed error-checking for clarity, but none of the SDL API calls fail in this example.) #include <SDL.h> int main(int argc, const char *argv[]) { SDL_Init( SDL_INIT_EVERYTHING ); SDL_Surface *screen = SDL_SetVideoMode( 640, 480, 32, SDL_HWSURFACE | SDL_DOUBLEBUF ); SDL_Surface *temp = SDL_CreateRGBSurface( SDL_HWSURFACE, 100, 100, 32, 0, 0, 0, ( SDL_BYTEORDER == SDL_BIG_ENDIAN ? 0x000000ff : 0xff000000 ) ); SDL_Surface *surface = SDL_DisplayFormatAlpha( temp ); SDL_FreeSurface( temp ); SDL_FillRect( surface, &surface->clip_rect, SDL_MapRGBA( screen->format, 0x00, 0xff, 0x00, 0xff ) ); SDL_Rect r; r.x = 50; r.y = 50; SDL_BlitSurface( surface, NULL, screen, &r ); SDL_Flip( screen ); SDL_Delay( 1000 ); SDL_Quit(); return 0; }

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  • I am looking to make a spaceship tilt as it corners but I cant get it to return

    - by bobthemac
    I am using the TL game engine I am not allowed to use a physics engine but I need to make the spaceship lean as it corners, I can make it lean but cannot make it return to its starting position. I have looked at implementing some kind of spring physics but I don't understand it. Here is my code so far if(myEngine->KeyHeld(Key_A)) { car->RotateY(carSteer * frameTime); if(carSteer >= -carMaxSteer) { carSteer -= carSteerIncrement; car->RotateLocalZ(-(carSteer * frameTime)); } } if(!myEngine->KeyHeld(Key_A)) { if(carSteer < 0) { carSteer = 0; } } if(myEngine->KeyHeld(Key_D)) { car->RotateY(carSteer * frameTime); if(carSteer <= carMaxSteer) { carSteer += carSteerIncrement; car->RotateLocalZ(-(carSteer * frameTime)); } } if(!myEngine->KeyHeld(Key_D)) { if(carSteer > 0) { carSteer = 0; } } All the functions I am calling are built into the engine and I did not write them. Any Help Would Be Appreciated Thanks.

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  • android multitouch problem

    - by Max
    Im aware that there a a couple of posts on this matter, but Ive tried all of them and none of them gets rid of my problem. Im starting to get close to the end of my game so I bought a cabel to try it on a real phone, and as I expected my multitouch dosnt work. I use 2 joysticks, one to move my character and one to change his direction so he can shoot while walking backwards etc. my local variable: public void update(MotionEvent event) { if (event == null && lastEvent == null) { return; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } int index = event.getActionIndex(); int pointerId = event.getPointerId(index); statement for left Joystick: if (pointerId == 0 && event.getAction() == MotionEvent.ACTION_DOWN && (int) event.getX() > steeringxMesh - 50 && (int) event.getX() < steeringxMesh + 50 && (int) event.getY() > yMesh - 50 && (int) event.getY() < yMesh + 50) { dragging = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { dragging = false; } if (dragging) { //code for moving my character statement for my right joystick: if (pointerId == 1 && event.getAction() == MotionEvent.ACTION_DOWN && (int) event.getX() > shootingxMesh - 50 && (int) event.getX() < shootingxMesh + 50 && (int) event.getY() > yMesh - 50 && (int) event.getY() < yMesh + 50) { shooting = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { shooting = false; } if (shooting) { // code for aiming } This class is my main-Views onTouchListener and is called in a update-method that gets called in my game-loop, so its called every frame. Im really at a loss here, I've done a couple of tutorials and Ive tried all relevant solutions to similar posts. Can post entire Class if necessary but I think this is all the relevant code. Just hope someone can make some sence out of this.

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  • How to determine collision direction between two rectangles?

    - by Jon
    I am trying to figure out how to determine the direction a collision occurs between two rectangles. One rectangle does not move. The other rectangle has a velocity in any direction. When a collision occurs, I want to be able to set the position of the moving rectangle to the point of impact. I seem to be stuck in determining from what direction the impact occurs. If I am moving strictly vertically or horizontally I manage great detection. But when moving in both directions at the same time, strange things happen. What is the best way to determine what direction a collision occurs between two rectangles?

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  • Deep Cloning C++ class that inherits CCNode in Cocos2dx

    - by A Devanney
    I stuck with something in Cocos2dx ... I'm trying to deep clone one of my classes that inherits CCNode. Basically i have.... GameItem* pTemp = new GameItem(*_actualItem); // loops through all the blocks in gameitem and updates their position pTemp->moveDown(); // if in boundary or collision etc... if (_gameBoard->isValidMove(pTemp)) { _actualItem = pTemp; // display the position CCLog("pos (1) --- (X : %d,Y : %d)", _actualItem->getGridX(),_actualItem->getGridY()); } Then doesn't work, because the gameitem inherits CCNode and has the collection of another class that also inherits CCNode. its just creating a shallow copy and when you look at children of the gameitem node in the copy, just point to the original? class GameItem : public CCNode { // maps to the actual grid position of the shape CCPoint* _rawPosition; // tracks the current grid position int _gridX, _gridY; // tracks the change if the item has moved CCPoint _offset; public: //constructors GameItem& operator=(const GameItem& item); GameItem(Shape shape); ... } then in the implementation.... GameItem& GameItem::operator=(const GameItem& item) { _gridX = item.getGridX(); _gridY = item.getGridY(); _offset = item.getOffSet(); _rawPosition = item.getRawPosition(); // how do i copy the node? return *this; } // shape contains an array of position for the game character GameItem::GameItem(Shape shape) { _rawPosition = shape.getShapePositions(); //loop through all blocks in position for (int i = 0; i < 7; i++) { // get the position of the first block in the shape and add to the position of the first block int x = (int) (getRawPosition()[i].x + getGridX()); int y = (int) (getRawPosition()[i].y + getGridY()); //instantiate a block with the position and type Block* block = Block::blockWithFile(x,y,(i+1), shape); // add the block to the this node this->addChild(block); } } And for clarity here is the block class class Block : public CCNode{ private: // using composition over inheritance CCSprite* _sprite; // tracks the current grid position int _gridX, _gridY; // used to store actual image number int _blockNo; public: Block(void); Block(int gridX, int gridY, int blockNo); Block& operator=(const Block& block); // static constructor for the creation of a block static Block* blockWithFile(int gridX, int gridY,int blockNo, Shape shape); ... } The blocks implementation..... Block& Block::operator=(const Block& block) { _sprite = new CCSprite(*block._sprite); _gridX = block._gridX; _gridY = block._gridY; _blockNo = block._blockNo; //again how to clone CCNode? return *this; } Block* Block::blockWithFile(int gridX, int gridY,int blockNo, Shape shape) { Block* block = new Block(); if (block && block->initBlockWithFile(gridX, gridY,blockNo, shape)) { block->autorelease(); return block; } CC_SAFE_DELETE(block); return NULL; } bool Block::initBlockWithFile(int gridX, int gridY,int blockNo, Shape shape) { setGridX(gridX); setGridY(gridY); setBlockNo(blockNo); const char* characterImg = helperFunctions::Format(shape.getFileName(),blockNo); // add to the spritesheet CCTexture2D* gameArtTexture = CCTextureCache::sharedTextureCache()->addImage("Character.pvr.ccz"); CCSpriteBatchNode::createWithTexture(gameArtTexture); // block settings _sprite = CCSprite::createWithSpriteFrameName(characterImg); // set the position of the block and add it to the layer this->setPosition(CONVERTGRIDTOACTUALPOS_X_Y(gridX,gridY)); this->addChild(_sprite); return true; } Any ideas are welcome at this point!! thanks

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  • Having trouble's understanding NIF model file format?

    - by NoobScratcher
    I'm attempting too develop a 3rd party application to make it easy to import 3d model part's into my mod for skyrim the plan was to have a fileviewer and preview window of the nif model but since , I don't know what the NIF file format actually is or where to get the vertex data from it or the hole nine yards of parsing a text file in detail I'm at a lost what to do. I'm very good at C++ but not at this super over complicated file formats , id much prefer .obj over the nif file format specification here -- http://niftools.sourceforge.net/doc/nif/index.html If someone could help me in understanding the file format in a natural and simple way and the exact parsing needed to create the 3D Model in the frustum and a explanation on how you figured that out would be happy to know. I use cygwin , notepad++ , win32 7

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  • Why isn't one of the constant buffers being loaded inside the shader?

    - by Paul Ske
    I however got the model to load under tessellation; only problem is that one of the constant buffers aren't actually updating the shader's tessellation factor inside the hullshader. I created a messagebox at the rendering point so I know for sure the tessellation factor is assigned to the dynamic constant buffer. Inside the shader code where it says .Edges[1] = tessellationAmount; the tessellationAmount is suppose to be sent from the dynamic buffer to the shader. Otherwise it's just a plain box. In better explanation; there's a matrixBuffer, cameraBuffer, TessellationBuffer for constant. There's a multiBuffer array that assigns the matrix, camera, tesselation. So, when I set the Hull Shader, PixelShader, VertexShader, DomainShader it gets assigned by the multibuffer. E.G. devcon-HSSetConstantBuffers(0,3,multibuffer); The only way around the whole ideal would be to go in the shader and change how much the edges tessellate and inside the edges as well with the same number. My question is why wouldn't the tessellationBuffer not work in the shader?

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  • Using OpenCl to jiggle the Pipe

    - by TOAOGG
    I've got the Idea to use OpenCL to program a simple Renderer. A clear contra is, that this approach won't benefit from the hardware as the functions on the device (I think). Would it be useful to do this in OpenCL..lets say we want to Cull as early as possible so we won't have many per vertex operations. Is it correct, that Culling is done after the Vertex-Shader? For static-vertecies who won't get effected by the shader it could be interesting to cull them before. Another idea would be an deferred renderer. So the main question is: Would it make sense to program a renderer in OpenCL (aside the effort)? The resulting picture would be drawn in OpenGL.

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  • Playing a sound on collision?

    - by Eric McLoughlin
    I'm making a pool game. I've separated the gameplay logic and the physics into two systems, entities and physics. Each entity holds a reference to a body which the physics system uses. The body itself holds a reference back to it's owner. When an entity collides with another entity, the Collided(Entity other) method is called on both. What I'm trying to do now is to play a sound when both entities colliding are of a certain subclass. I'm not sure how to do that. I could do it in the Collided method, but then the sound would be played two times at the same time, since the method was called on both entities. How do you suggest I do this?

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  • Isometric Collision Detection

    - by Sleepy Rhino
    I am having some issues with trying to detect collision of two isometric tile. I have tried plotting the lines between each point on the tile and then checking for line intercepts however that didn't work (probably due to incorrect formula) After looking into this for awhile today I believe I am thinking to much into it and there must be a easier way. I am not looking for code just some advise on the best way to achieve detection of overlap

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  • Determining the angle to fire a shot when target and shooter moves, and bullet moves with shooter velocity added in

    - by Azaral
    I saw this question: Predicting enemy position in order to have an object lead its target and followed the link in the answer to stack overflow. In the stack overflow page I used the 2nd answer, the one that is a large mathematical derivation. My situation is a little different though. My first question though is will the answer provided in the stack overflow page even work to begin with, assuming the original circumstances of moving target and stationary shooter. My situation is a little different than that situation. My target moves, the shooter moves, and the bullets from the shooter start off with the velocities in x and y added to the bullets' x and y velocities. If you are sliding to the right, the bullets will remain in front of you as you move so as long as your velocity remains constant. What I'm trying to do is to get the enemy to be able to determine where they need to shoot in order to hit the player. Unless the player and enemy is stationary, the velocity from the ship adding to the velocity of the bullets will cause a miss. I'd rather like to prevent that. I used the formula in the stack overflow answer and did what I thought were the appropriate adjustments. I've been banging at this for the last four hours and I just can't make it click. It is probably something really simple and boneheaded that I am missing (that seems to be a lot of my problems lately). Here is the solution presented from the stack overflow answer: It boils down to solving a quadratic equation of the form: a * sqr(x) + b * x + c == 0 Note that by sqr I mean square, as opposed to square root. Use the following values: a := sqr(target.velocityX) + sqr(target.velocityY) - sqr(projectile_speed) b := 2 * (target.velocityX * (target.startX - cannon.X) + target.velocityY * (target.startY - cannon.Y)) c := sqr(target.startX - cannon.X) + sqr(target.startY - cannon.Y) Now we can look at the discriminant to determine if we have a possible solution. disc := sqr(b) - 4 * a * c If the discriminant is less than 0, forget about hitting your target -- your projectile can never get there in time. Otherwise, look at two candidate solutions: t1 := (-b + sqrt(disc)) / (2 * a) t2 := (-b - sqrt(disc)) / (2 * a) Note that if disc == 0 then t1 and t2 are equal. If there are no other considerations such as intervening obstacles, simply choose the smaller positive value. (Negative t values would require firing backward in time to use!) Substitute the chosen t value back into the target's position equations to get the coordinates of the leading point you should be aiming at: aim.X := t * target.velocityX + target.startX aim.Y := t * target.velocityY + target.startY Here is my code, after being corrected by Sam Hocevar (thank you again for your help!). It still doesn't work. For some reason it never enters the section of code inside the if(disc = 0) (obviously because it is always less than zero but...). However, if I plug the numbers from my game log on the enemy and player positions and velocities it outputs a valid firing solution. I have looked at the code side by side a couple of times now and I can't find any differences. There has got to be something simple I'm missing here. If someone else could look at this code and determine what is going on here I'd appreciate it. I know it's not going through that section because if it were, shouldShoot would become true and the enemy would be blasting away at the player. This section calls the function in question, CalculateShootHeading() if(shouldMove) { UseEngines(); } x += xVelocity; y += yVelocity; CalculateShootHeading(); if(shouldShoot) { ShootWeapons(); } UpdateWeapons(); This is CalculateShootHeading(). This is inside the enemy class so x and y are the enemy's x and y and the same with velocity. One output from my game log gives Player X = 2108, Player Y = -180.956, Player X velocity = 10.9949, Player Y Velocity = -6.26017, Enemy X = 1988.31, Enemy Y = -339.051, Enemy X velocity = 1.81666, Enemy Y velocity = -9.67762, 0 enemy projectiles. The output from the console tester is Bullet position = 2210.49, -239.313 and Player Position = 2210.49, -239.313. This doesn't make any sense. The only thing that could be different is the code or the input into my function in the game and I've checked that and I don't think that it is wrong as it's updated before this and never changed. float const bulletSpeed = 30.f; float const dx = playerX - x; float const dy = playerY - y; float const vx = playerXVelocity - xVelocity; float const vy = playerYVelocity - yVelocity; float const a = vx * vx + vy * vy - bulletSpeed * bulletSpeed; float const b = 2.f * (vx * dx + vy * dy); float const c = dx * dx + dy * dy; float const disc = b * b - 4.f * a * c; shouldShoot = false; if (disc >= 0.f) { float t0 = (-b - std::sqrt(disc)) / (2.f * a); float t1 = (-b + std::sqrt(disc)) / (2.f * a); if (t0 < 0.f || (t1 < t0 && t1 >= 0.f)) { t0 = t1; } if (t0 >= 0.f) { float shootx = vx + dx / t0; float shooty = vy + dy / t0; heading = std::atan2(shooty, shootx) * RAD2DEGREE; } shouldShoot = true; }

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  • How do I implement a "sliding out of / into" effect on a settings menu similar to that in Angry Birds?

    - by VictorB
    I'm trying to implement a settings menu component similar to that in Angry Birds - a button control that makes an options menu slide out of it and back into it when clicked on. I use scene2d.ui to build the UI components: a Button in a Table to implement the button control, a Table to implement the options menu, and a Stack to lay these out one on top of the other and at this moment I have the following behavior: When the user hits the button control for the first time, then the alpha of the table component is set to 1; When the user hits the button control the second time, then the alpha of the table component is set to 0; And so on. Any ideas how I can get the sliding out of and into effect on user clicks with libgdx? Similar to what Angry Birds provides. Maybe using the TweenEngine, actions, interpolations, combinations of these? Thanks in advance.

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  • Drawing two orthogonal strings in 3d space in Android Canvas?

    - by hasanghaforian
    I want to draw two strings in canvas.First string must be rotated around Y axis,for example 45 degrees.Second string must be start at the end of first string and also it must be orthogonal to first string. This is my code: String text = "In the"; float textWidth = redPaint.measureText(text); Matrix m0 = new Matrix(); Matrix m1 = new Matrix(); Matrix m2 = new Matrix(); mCamera = new Camera(); canvas.setMatrix(null); canvas.save(); mCamera.rotateY(45); mCamera.getMatrix(m0); m0.preTranslate(-100, -100); m0.postTranslate(100, 100); canvas.setMatrix(m0); canvas.drawText(text, 100, 100, redPaint); mCamera = new Camera(); mCamera.rotateY(90); mCamera.getMatrix(m1); m1.preTranslate(-textWidth - 100, -100); m1.postTranslate(textWidth + 100, 100); m2.setConcat(m1, m0); canvas.setMatrix(m2); canvas.drawText(text, 100 + textWidth, 100, greenPaint); But in result,only first string(text with red font)is visible. How can I do drawing two orthogonal strings in 3d space?

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  • Instead of the specified Texture, black circles on a green background are getting rendered. Why?

    - by vinzBad
    I'm trying to render a Texture via OpenGL. But instead of the texture black circles on a green background are rendered. (They scale, depending what the rotation of the texture is) Example: The texture I'm trying to render is the following: This is the code I use to render the texture, it's located in my Sprite-class. public void Render() { Matrix4 matrix = Matrix4.CreateTranslation(-OriginX, -OriginY, 0) * Matrix4.CreateRotationZ(Rotation) * Matrix4.CreateTranslation(X, Y, 0); Vector2[] corners = { new Vector2(0,0), //top left new Vector2(Width ,0),//top right new Vector2(Width,Height),//bottom rigth new Vector2(0,Height)//bottom left }; //copy the corners to the uv coordinates Vector2[] uv = corners.ToArray<Vector2>(); //transform the coordinates for (int i = 0; i < 4; i++) corners[i] = new Vector2(Vector3.Transform(new Vector3(corners[i]), matrix)); //GL.Color3(TintColor); GL.BindTexture(TextureTarget.Texture2D, _ID); GL.Begin(BeginMode.Quads); { for (int i = 0; i < 4; i++) { GL.TexCoord2(uv[i]); GL.Vertex3(corners[i].X, corners[i].Y, _layerDepth); } } GL.End(); if (EnableDebugDraw) { GL.Color3(Color.Violet); GL.PointSize(3); GL.Begin(BeginMode.Points); { for (int i = 0; i < 4; i++) GL.Vertex2(corners[i]); } GL.End(); GL.Color3(Color.Green); GL.Begin(BeginMode.Points); GL.Vertex2(X, Y); GL.End(); } } This is how I setup OpenGL. public static void SetupGL() { GL.Enable(EnableCap.AlphaTest); GL.AlphaFunc(AlphaFunction.Greater, 0.1f); GL.Enable(EnableCap.Texture2D); GL.Hint(HintTarget.PerspectiveCorrectionHint, HintMode.Nicest); } With this function I load the texture: public static uint LoadTexture(string path) { uint id; GL.GenTextures(1, out id); GL.BindTexture(TextureTarget.Texture2D, id); Bitmap bitmap = new Bitmap(path); BitmapData data = bitmap.LockBits(new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb); GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, data.Width, data.Height, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, data.Scan0); bitmap.UnlockBits(data); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Linear); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear); return id; } And here I call Sprite.Render() protected override void OnRenderFrame(FrameEventArgs e) { GL.ClearColor(Color.MidnightBlue); GL.Clear(ClearBufferMask.ColorBufferBit); _sprite.Render(); SwapBuffers(); base.OnRenderFrame(e); } As I stole this code from the Textures-Example from OpenTK, I don't understand why this doesn't work.

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  • How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

    - by Register Sole
    Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they would swing! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :) EDIT In response to Cholesky's comment about warm starting the solver and Baumgarte: Oh right, I forgot to mention! I do save the contact history and the impulse determined in this time step to be used as initial guess in the next time step. As for the Baumgarte, here's what actually happens in the code. Collision is detected when the bodies' closest distance is less than SKIN, meaning they are actually still separated. If at this moment, I used the PGS solver without Baumgarte, restitution of 0 alone would be able to stop the bodies, separated by a distance of ~SKIN, in mid-air! So this isn't right, I want to have the bodies touching each other. So I turn on the Baumgarte, where its role is actually to pull the bodies together! Weird I know, a scheme intended to push the body apart becomes useful for the reverse. Also, I found that if I increase the number of iteration to 100, stacks become much more stable, though the program becomes so slow. UPDATE Since the stack swings left and right, could it be something is wrong with my friction model? Current friction constraint: relative_tangential_velocity = 0

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  • Tips on how to notify a user of new features in your game (Android)

    - by brent777
    I have noticed a problem when releasing new features for a game that I wrote for Android and published on Google Play Store. Because my game is "stage-based" - and not a game like Hay Day, for example, where users will just go into the game every day since it can't really be finished - my users are not aware of new features that I release for the game. For example, if I publish a new version of my game and it contains a couple new stages, most of their devices will just auto-update the game and they don't even notice this and think to check out what's new. So this is why an approach like popping open a dialog that showcases the new feature(s) when they open the game for the first time after the update was done is not really sufficient. I am looking for some tips on an approach that will draw my users back into the game and then they could read more detail about new features on such a dialog. I was thinking of something like a notification that tells them to check out the new features after an update is done but I am not sure if this is a good idea. Any suggestions to help me solve this problem would be awesome.

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  • What is involved with writing a lobby server?

    - by Kira
    So I'm writing a Chess matchmaking system based on a Lobby view with gaming rooms, general chat etc. So far I have a working prototype but I have big doubts regarding some things I did with the server. Writing a gaming lobby server is a new programming experience to me and so I don't have a clear nor precise programming model for it. I also couldn't find a paper that describes how it should work. I ordered "Java Network Programming 3rd edition" from Amazon and still waiting for shipment, hopefully I'll find some useful examples/information in this book. Meanwhile, I'd like to gather your opinions and see how you would handle some things so I can learn how to write a server correctly. Here are a few questions off the top of my head: (may be more will come) First, let's define what a server does. It's primary functionality is to hold TCP connections with clients, listen to the events they generate and dispatch them to the other players. But is there more to it than that? Should I use one thread per client? If so, 300 clients = 300 threads. Isn't that too much? What hardware is needed to support that? And how much bandwidth does a lobby consume then approx? What kind of data structure should be used to hold the clients' sockets? How do you protect it from concurrent modification (eg. a player enters or exists the lobby) when iterating through it to dispatch an event without hurting throughput? Is ConcurrentHashMap the correct answer here, or are there some techniques I should know? When a user enters the lobby, what mechanism would you use to transfer the state of the lobby to him? And while this is happening, where do the other events bubble up? Screenshot : http://imageshack.us/photo/my-images/695/sansrewyh.png/

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  • How to prevent overlapping of gunshot sounds when using fast-firing weapons

    - by G3tinmybelly
    So I am now trying to find sounds for my guns but when I grab a gun sound effect and play it in my game a lot of the sounds are either terrible sounding or have this horrible echoing effect because as a gun shoots sometimes the previous sound is playing still. public void shoot(float x, float y, float direction){ if(empty){ PlayHUD.message = "No more bullets!"; return; } if(reloading){ return; } if(System.currentTimeMillis() - lastShot < fireRate){ //AssetsLoader.lmgSound.stop(); return; } float dx = (float) (-13 * Math.cos(direction) + 75 * Math.sin(direction)); float dy = (float) (-14 * -Math.sin(direction) + 75 * Math.cos(direction)); float dx1 = (float) (-13 * Math.cos(direction) + 75 * Math.sin(direction)); float dy1 = (float) (-14 * -Math.sin(direction) + 75 * Math.cos(direction)); PlayState.effects.add(new MuzzleFlashEffect(x + dx1, y + dy1, (float) Math.toDegrees(-direction))); PlayState.projectiles.add(new Bullet(this, x + dx, y + dy, (float) (direction + (Math.toRadians(MathUtils.random(-accuracy, accuracy)))))); if(OptionState.soundOn){ AssetsLoader.lmgSound.play(OptionState.volume); } bulletsInClip--; lastShot = System.currentTimeMillis(); } Here is the code for where the sound plays. Every time this method is called the sound is called but it happens so often in this case that there is this terrible echoing. Any idea on how to fix this?

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  • Windows Phone XAML and XNA Apps with Game Components

    - by row1
    I am using the Windows Phone Template "Windows Phone XAML and XNA Apps" and targeting Windows Phone 7/8. Most examples show your game inheriting from Microsoft.Xna.Framework.Game and then adding Microsoft.Xna.Framework.GameComponent items to the Components collection. But as my game page inherits from PhoneApplicationPage there isn't a Components collection or a Game property. How can I use GameComponent from within PhoneApplicationPage?

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  • Dirt compression from vehicle tires

    - by Mungoid
    So I kinda have this working but its not correct because it just averages, so I wanted to know if anyone here has any ideas. I'm trying to simulate loose dirt compression under the tires of a vehicle to reduce the potential bumpiness of 'chunky' terrain. Currently how I do this is that I have a bounding box shape around my tires, set a little lower so they intersect with the terrain. Each frame, I (currently) average all of the heights of each point in the terrain that are within the box bounds of that tire, and then set them all to that average. Clearly this won't work in most cases because, for example, if i'm on a hill, the terrain will deform way too much. One way I thought was to have a max and min amount the points could raise and lower but that still doesn't seem to work properly and sometimes looks more like steps than smooth dirt. I wanna say that there is probably a bit more to this that what i'm currently doing but I am not sure where to look. Could anyone here shed some light on this subject? Would I benefit any by maybe looking up some smoothing algorith or something similar?

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  • How to draw unlimited FPS on Mac OS X with OpenGL?

    - by V1ru8
    I d'like to draw as many frames as possible with OpenGL on Mac OS X to measure the performance on different scenes. What I've tried so far: Using a CVDisplayLink that has NSOpenGLCPSwapInterval set to 0, so it does not sync with the Display. But with that it's still stuck at max 60FPS Using normal -drawRect: with a timer that fires 1/1000sec and calls -setNeedsDisplay: Still not more than 60FPS Same as 2. but I call -display in the timer callback. With that I get the FPS above 60, but it still stops at 100-110 FPS. Although the frame rate should easily be at 10times more. Andy idea how I can really draw as many frames as possible?

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