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• Need a bounding box for CCSprite that includes all children/subchildren

  - by prototypical

  I have a CCSprite that has CCSprite children, and those CCSprite children have CCSprite children. The contentSize property doesn't seem to include all children/subchildren, and seems to only work for the base node. I could write a recursive method to traverse a CCSprite for all children/subchildren and calculate a proper boundingbox, but am curious as to if I am missing something and it's possible to get that information without doing so. I'l be a little surprised if such a method doesn't exist, but I can't seem to find it.

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• Quaternion LookAt for camera

  - by Homar

  I am using the following code to rotate entities to look at points. glm::vec3 forwardVector = glm::normalize(point - position); float dot = glm::dot(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector); float rotationAngle = (float)acos(dot); glm::vec3 rotationAxis = glm::normalize(glm::cross(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector)); rotation = glm::normalize(glm::quat(rotationAxis * rotationAngle)); This works fine for my usual entities. However, when I use this on my Camera entity, I get a black screen. If I flip the subtraction in the first line, so that I take the forward vector to be the direction from the point to my camera's position, then my camera works but naturally my entities rotate to look in the opposite direction of the point. I compute the transformation matrix for the camera and then take the inverse to be the View Matrix, which I pass to my OpenGL shaders: glm::mat4 viewMatrix = glm::inverse( cameraTransform->GetTransformationMatrix() ); The orthographic projection matrix is created using glm::ortho. What's going wrong?

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• Rope Colliding with a Rectangle

  - by Colton

  I have my rope, and I have my rectangles. The rope is similar to the implementation found here: http://nehe.gamedev.net/tutorial/rope_physics/17006/ Now, I want to make the rope properly collide with the rectangle such that the rope will not pass through a rectangle, and wrap around the rectangle and all that good stuff. Currently, I have it set so no rope node can pass through a rect (successfully), however, this means a rope segment can still pass through a block. Ex: So the question is, what can I do to fix this? What I have tried: I create a rectangle between two nodes of a rope, calculate rotation between the nodes, and get myself a transformed rectangle. I can successfully detect a collision between rope segments and a (non-transformed) rectangle. Create a new node or pivot point around the corner of the block, and rearrange nodes to point to the corner node. Trouble is determining what corner the rope segment is passing through. And then the current rope setup goes wonky (based on verlet integration, so a sudden change in position causes the rope to wiggle like a seismograph during a magnitude 8 earth quake.) Among other issues that might be solvable, but its turning into a case by case thing, which doesn't seem right. I think the best answer here would just be a link to a tutorial (I simply can't find any, most lead to box2D or farseer, but I want to at least learn how it works before I hide behind an engine).

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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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• Drawing a sprite or text causes the OpenGl rendering to 'disappear' in SFML

  - by Ken

  I'm using some SFML built in functions to draw sprites and text as an overlay on top of some OpenGL rending in an SFML RenderWindow. The opengl rendering appears fine until I add the code to draw the sprites or text. The sprite or text drawing causes the OpenGL stuff to disappear. The follow code show what I'm trying to do sf::RenderWindow window(sf::VideoMode(viewport.width,viewport.height,32), "SFML Window"); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0,viewport.width,0,viewport.height,0,1); while (window.pollEvent(Event)) { //event handling... //begin drawing glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glBegin(GL_TRIANGLES); glColor3f(col.x,col.y,col.z); for(int i=0;i<3;i++) glVertex2f(pos.x+verts[i].x,pos.y+verts[i].y); glEnd(); // adding this line causes all the previous opengl triangles not to appear window.draw("Sometext"); window.display(); }

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• How to use mount points in MilkShape models?

  - by vividos

  I have bought the Warriors & Commoners model pack from Frogames and the pack contains (among other formats) two animated models and several non-animated objects (axe, shield, pilosities, etc.) in MilkShape3D format. I looked at the official "MilkShape 3D Viewer v2.0" (msViewer2.zip at http://www.chumba.ch/chumbalum-soft/ms3d/download.html) source code and implemented loading the model, calculating the joint matrices and everything looks fine. In the model there are several joints that are designated as the "mount points" for the static objects like axe and shield. I now want to "put" the axe into the hand of the animated model, and I couldn't quite figure out how. I put the animated vertices in a VBO that gets updated every frame (I know I should do this with a shader, but I didn't have time to do this yet). I put the static vertices in another VBO that I want to keep static and not updated every frame. I now tried to render the animated vertices first, then use the joint matrix for the "mount joint" to calculate the location of the static object. I tried many things, and what about seems to be right is to transpose the joint matrix, then use glMatrixMult() to transform the modelview matrix. For some objects like the axe this is working, but not for others, e.g. the pilosities. Now my question: How is this generally implemented when using bone/joint models, and especially with MilkShape3D models? Am I on the right track?

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• How can I select an audio output device in directshow

  - by Vibhore Tanwer

  I was wondering how I can select the output device for audio in directshow. I am able to get available audio output devices in directshow. But how can I make one of these to be audio output device. Its always going for the default audio device. I want to be able to output audio on my choice of device. I have been struggling through google but couldn't find anything useful. All I could get was this link but it doesn't really solve my problem. Any help will be really helpful for me.

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• Generate texture for a heightmap

  - by James

  I've recently been trying to blend multiple textures based on the height at different points in a heightmap. However i've been getting poor results. I decided to backtrack and just attempt to recreate one single texture from an SDL_Surface (i'm using SDL) and just send that into opengl. I'll put my code for creating the texture and reading the colour values. It is a 24bit TGA i'm loading, and i've confirmed that the rest of my code works because i was able to send the surfaces pixels directly to my createTextureFromData function and it drew fine. struct RGBColour { RGBColour() : r(0), g(0), b(0) {} RGBColour(unsigned char red, unsigned char green, unsigned char blue) : r(red), g(green), b(blue) {} unsigned char r; unsigned char g; unsigned char b; }; // main loading code SDLSurfaceReader* reader = new SDLSurfaceReader(m_renderer); reader->readSurface("images/grass.tga"); // new texture unsigned char* newTexture = new unsigned char[reader->m_surface->w * reader->m_surface->h * 3 * reader->m_surface->w]; for (int y = 0; y < reader->m_surface->h; y++) { for (int x = 0; x < reader->m_surface->w; x += 3) { int index = (y * reader->m_surface->w) + x; RGBColour colour = reader->getColourAt(x, y); newTexture[index] = colour.r; newTexture[index + 1] = colour.g; newTexture[index + 2] = colour.b; } } unsigned int id = m_renderer->createTextureFromData(newTexture, reader->m_surface->w, reader->m_surface->h, RGB); // functions for reading pixels RGBColour SDLSurfaceReader::getColourAt(int x, int y) { Uint32 pixel; Uint8 red, green, blue; RGBColour rgb; pixel = getPixel(m_surface, x, y); SDL_LockSurface(m_surface); SDL_GetRGB(pixel, m_surface->format, &red, &green, &blue); SDL_UnlockSurface(m_surface); rgb.r = red; rgb.b = blue; rgb.g = green; return rgb; } // this function taken from SDL documentation // http://www.libsdl.org/cgi/docwiki.cgi/Introduction_to_SDL_Video#getpixel Uint32 SDLSurfaceReader::getPixel(SDL_Surface* surface, int x, int y) { int bpp = m_surface->format->BytesPerPixel; Uint8 *p = (Uint8*)m_surface->pixels + y * m_surface->pitch + x * bpp; switch (bpp) { case 1: return *p; case 2: return *(Uint16*)p; case 3: if (SDL_BYTEORDER == SDL_BIG_ENDIAN) return p[0] << 16 | p[1] << 8 | p[2]; else return p[0] | p[1] << 8 | p[2] << 16; case 4: return *(Uint32*)p; default: return 0; } } I've been stumped at this, and I need help badly! Thanks so much for any advice.

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• Are there any preexisting maps for a Minecraft-like level I could use in my engine?

  - by Rishav Sharan

  I am working on a tiny cube-based engine like Minecraft. I was wondering if there is a way for me to get large blocky terrain in a text format that I can use for rendering on my engine? I don't want to start on procedural generation now, I just want a resource where I can get the coord list for a pretty looking terrain. Alternatively, is it possible for me to parse the Minecraft world files and use that data to generate terrain/buildings in my code?

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• Creating a voxel chunk with a VBO - How to translate the coordinates of each block and add it to the VBO chunk?

  - by sunsunsunsunsun

  Im trying to make a voxel engine similar to minecraft as a little learning experience and a way to learn some opengl. I have created a chunk class and I want to put all of the vertices for the whole chunk into a single VBO. I was previously only putting each block into a vbo and making a call to render each block. Anyways, I am a bit confused about how I can translate the coordinates of each block in the chunk when I'm putting all vertices into one vbo. This is what I have at the moment. public void putVertices(float tx, float ty, float tz) { float l_length = 1.0f; float l_height = 1.0f; float l_width = 1.0f; vertexPositionData.put(new float[]{ xOffset + l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, l_height + ty,zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + l_width + tz, xOffset + l_length + tx, l_height + ty,zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz }); } public void createChunk() { vertexPositionData = BufferUtils.createFloatBuffer((24*3)*activateBlocks); Random random = new Random(); for (int x = 0; x < CHUNK_SIZE; x++) { for (int y = 0; y < CHUNK_SIZE; y++) { for (int z = 0; z < CHUNK_SIZE; z++) { if(blocks[x][y][z].getActive()) { putVertices(x*2.0f, y*2.0f, z*2.0f); } } } } Whats any easy way to translate the vertices of each block into its correct position? I was previously using glTranslatef with each call to render block but this wont work now. What I am doing now also does not work, the blocks all render in stacks on top of each other and it looks like this: http://i.imgur.com/NyFtBTI.png Thanks

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• XNA Drag Gestures - fractional delta values

  - by Den

  I have an issue with objects moving roughly twice as far as expected when dragging them. I am comparing my application to the standard TouchGestureSample sample from MSDN. For some reason in my application gesture samples have fractional positions and deltas. Both are using same Microsoft.Xna.Framework.Input.Touch.dll, v4.0.30319. I am running both apps using standard Windows Phone Emulator. I am setting my break point immediately after this line of code in a simple Update method: GestureSample gesture = TouchPanel.ReadGesture(); Typical values in my app: Delta = {X:-13.56522 Y:4.166667} Position = {X:184.6956 Y:417.7083} Typical values in sample app: Delta = {X:7 Y:16} Position = {X:497 Y:244} Have anyone seen this issue? Does anyone have any suggestions? Thank you.

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• In esenthel engine how can I remove some object from Gui class?

  - by Gajet

  I know many people in this site may not know esenthel engine at all and my question may be better answered at engine forum but I'm putting it here to share the name of a real easy to code gameengine with all of you: you can easily add a Button for example to your GUI class (gui is it's shared instance) with Gui += buttonInstance.create("click on me") but I'm just wondering how can you remove an on object from from Gui members. as far as I know there is no such a method as removeChild or getChildren or anything similar.

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• Why does my program stutter so much?

  - by user36322

  I've been very frustrated trying to solve this. I've looked it up, and all the answers are the same: set IsFixedTimeStep = false. This doesn't help me at all, the program is still jittery and stutters. I have absolutely no idea what is going on, can you guys help? Code for movement (objects is a list): speed = Math.Min(speed + (speedIncrement * gameTime.ElapsedGameTime.Milliseconds / 200), maxSpeed); for (int i = objects.Count - 1; i >= 0; i--) { objects[i].rect.Y += (int)(speed * gameTime.ElapsedGameTime.Milliseconds); //Check if the object is past the screen. If it is, remove it if (objects[i].rect.Y > screenHeight) { objects.Remove(objects[i]); } }

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• Isometric layer moving inside map

  - by gronzzz

  i'm created isometric map and now trying to limit layer moving. Main idea, that i have left bottom, right bottom, left top, right top points, that camera can not move outside, so player will not see map out of bounds. But i can not understand algorithm of how to do that. It's my layer scale/moving code. - (void)touchBegan:(UITouch *)touch withEvent:(UIEvent *)event { _isTouchBegin = YES; } - (void)touchMoved:(UITouch *)touch withEvent:(UIEvent *)event { NSArray *allTouches = [[event allTouches] allObjects]; UITouch *touchOne = [allTouches objectAtIndex:0]; CGPoint touchLocationOne = [touchOne locationInView: [touchOne view]]; CGPoint previousLocationOne = [touchOne previousLocationInView: [touchOne view]]; // Scaling if ([allTouches count] == 2) { _isDragging = NO; UITouch *touchTwo = [allTouches objectAtIndex:1]; CGPoint touchLocationTwo = [touchTwo locationInView: [touchTwo view]]; CGPoint previousLocationTwo = [touchTwo previousLocationInView: [touchTwo view]]; CGFloat currentDistance = sqrt( pow(touchLocationOne.x - touchLocationTwo.x, 2.0f) + pow(touchLocationOne.y - touchLocationTwo.y, 2.0f)); CGFloat previousDistance = sqrt( pow(previousLocationOne.x - previousLocationTwo.x, 2.0f) + pow(previousLocationOne.y - previousLocationTwo.y, 2.0f)); CGFloat distanceDelta = currentDistance - previousDistance; CGPoint pinchCenter = ccpMidpoint(touchLocationOne, touchLocationTwo); pinchCenter = [self convertToNodeSpace:pinchCenter]; CGFloat predictionScale = self.scale + (distanceDelta * PINCH_ZOOM_MULTIPLIER); if([self predictionScaleInBounds:predictionScale]) { [self scale:predictionScale scaleCenter:pinchCenter]; } } else { // Dragging _isDragging = YES; CGPoint previous = [[CCDirector sharedDirector] convertToGL:previousLocationOne]; CGPoint current = [[CCDirector sharedDirector] convertToGL:touchLocationOne]; CGPoint delta = ccpSub(current, previous); self.position = ccpAdd(self.position, delta); } } - (void)touchEnded:(UITouch *)touch withEvent:(UIEvent *)event { _isDragging = NO; _isTouchBegin = NO; // Check if i need to bounce _touchLoc = [touch locationInNode:self]; } #pragma mark - Update - (void)update:(CCTime)delta { CGPoint position = self.position; float scale = self.scale; static float friction = 0.92f; //0.96f; if(_isDragging && !_isScaleBounce) { _velocity = ccp((position.x - _lastPos.x)/2, (position.y - _lastPos.y)/2); _lastPos = position; } else { _velocity = ccp(_velocity.x * friction, _velocity.y *friction); position = ccpAdd(position, _velocity); self.position = position; } if (_isScaleBounce && !_isTouchBegin) { float min = fabsf(self.scale - MIN_SCALE); float max = fabsf(self.scale - MAX_SCALE); int dif = max > min ? 1 : -1; if ((scale > MAX_SCALE - SCALE_BOUNCE_AREA) || (scale < MIN_SCALE + SCALE_BOUNCE_AREA)) { CGFloat newSscale = scale + dif * (delta * friction); [self scale:newSscale scaleCenter:_touchLoc]; } else { _isScaleBounce = NO; } } }

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• Calculate velocity of a bullet ricocheting on a circle

  - by SteveL

  I made a picture to demostrate what I need,basecaly I have a bullet with velocity and I want it to bounce with the correct angle after it hits a circle Solved(look the accepted answer for explain): Vector.vector.set(bullet.vel); //->v Vector.vector2.setDirection(pos, bullet.pos); //->n normal from center of circle to bullet float dot=Vector.vector.dot(Vector.vector2); //->dot product Vector.vector2.mul(dot).mul(2); Vector.vector.sub(Vector.vector2); Vector.vector.y=-Vector.vector.y; //->for some reason i had to invert the y bullet.vel.set(Vector.vector);

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• how can i get rotation vector from matrix4x4 in xna?

  - by mr.Smyle

  i want to get rotation vector from matrix to realize some parent-children system for models. Matrix bonePos = link.Bone.Transform * World; Matrix m = Matrix.CreateTranslation(link.Offset) * Matrix.CreateScale(link.gameObj.Scale.X, link.gameObj.Scale.Y, link.gameObj.Scale.Z) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(link.gameObj.Rotation.Y), MathHelper.ToRadians(link.gameObj.Rotation.X), MathHelper.ToRadians(link.gameObj.Rotation.Z)) //need rotation vector from bone matrix here (now it's global model rotation vector) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(Rotation.Y), MathHelper.ToRadians(Rotation.X), MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(bonePos.Translation); link.gameObj.World = m; where : link - struct with children model settings, like position, rotation etc. And link.Bone - Parent Bone

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• How can I get started programming OpenGL on Mac OS X?

  - by Michael Stum

  I'm trying to start OpenGL programming on a Mac, which brings me into unknown territory on a lot of things. During the day, I'm a Web Developer, working in C# and before that in PHP and Delphi, all on Windows. During the night, I try to pick up Mac/OpenGL skills, but everything is so different. I've been trying to look for some books, but the OpenGL books are usually for iOS (tons of them out there) and the Mac Books usually cover "normal" application Development. I want to start simple with Pong, Tetris and Wolfenstein. I see that there are a bunch of different OpenGL Versions out there. I know about OpenGL ES 1&2, but I don't know about the "big" OpenGL Versions - which ones are commonly supported on 10.6 and 10.7 on current (2010/2011) Macs? Are there any up to date (XCode 4) books or tutorials? I don't want to use a premade Engine like Unity yet - again, I know next to nothing about any Mac development.

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• Why doesn't my texture display with this GLSL shader?

  - by Chewy Gumball

  I am trying to display a DXT1 compressed texture on a quad using a VBO and shaders, but I have been unable to get it working. All I get is a black square. I know my texture is uploaded properly because when I use immediate mode without shaders the texture displays fine but I will include that part just in case. Also, when I change the gl_FragColor to something like vec4 (0.0, 1.0, 1.0, 1.0) then I get a nice blue quad so I know that my shader is able to set the colour. It appears to be either the texture is not being bound correctly in the shader or the texture coordinates are not being picked up. However, I can't find the error! What am I doing wrong? I am using OpenTK in C# (not xna). Vertex Shader: void main() { gl_TexCoord[0] = gl_MultiTexCoord0; // Set the position of the current vertex gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } Fragment Shader: uniform sampler2D diffuseTexture; void main() { // Set the output color of our current pixel gl_FragColor = texture2D(diffuseTexture, gl_TexCoord[0].st); //gl_FragColor = vec4 (0.0,1.0,1.0,1.0); } Drawing Code: int vb, eb; GL.GenBuffers(1, out vb); GL.GenBuffers(1, out eb); // Position Texture float[] verts = { 0.1f, 0.1f, 0.0f, 0.0f, 0.0f, 1.9f, 0.1f, 0.0f, 1.0f, 0.0f, 1.9f, 1.9f, 0.0f, 1.0f, 1.0f, 0.1f, 1.9f, 0.0f, 0.0f, 1.0f }; uint[] indices = { 0, 1, 2, 0, 2, 3 }; //upload data to the VBO GL.BindBuffer(BufferTarget.ArrayBuffer, vb); GL.BindBuffer(BufferTarget.ElementArrayBuffer, eb); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(verts.Length * sizeof(float)), verts, BufferUsageHint.StaticDraw); GL.BufferData(BufferTarget.ElementArrayBuffer, (IntPtr)(indices.Length * sizeof(uint)), indices, BufferUsageHint.StaticDraw); //Upload texture int buffer = GL.GenTexture(); GL.BindTexture(TextureTarget.Texture2D, buffer); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (float)TextureWrapMode.Repeat); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (float)TextureWrapMode.Repeat); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (float)TextureMagFilter.Linear); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (float)TextureMinFilter.Linear); GL.TexEnv(TextureEnvTarget.TextureEnv, TextureEnvParameter.TextureEnvMode, (float)TextureEnvMode.Modulate); GL.CompressedTexImage2D(TextureTarget.Texture2D, 0, texture.format, texture.width, texture.height, 0, texture.data.Length, texture.data); //Draw GL.UseProgram(shaderProgram); GL.EnableClientState(ArrayCap.VertexArray); GL.EnableClientState(ArrayCap.TextureCoordArray); GL.VertexPointer(3, VertexPointerType.Float, 5 * sizeof(float), 0); GL.TexCoordPointer(2, TexCoordPointerType.Float, 5 * sizeof(float), 3); GL.ActiveTexture(TextureUnit.Texture0); GL.Uniform1(GL.GetUniformLocation(shaderProgram, "diffuseTexture"), 0); GL.DrawElements(BeginMode.Triangles, indices.Length, DrawElementsType.UnsignedInt, 0);

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• Drawing different per-pixel data on the screen

  - by Amir Eldor

  I want to draw different per-pixel data on the screen, where each pixel has a specific value according to my needs. An example may be a random noise pattern where each pixel is randomly generated. I'm not sure what is the correct and fastest way to do this. Locking a texture/surface and manipulating the raw pixel data? How is this done in modern graphics programming? I'm currently trying to do this in Pygame but realized I will face the same problem if I go for C/SDL or OpenGL/DirectX.

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• How to implement explosion in OpenGL with a particle effect?

  - 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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• Position Reconstruction from Depth by inverting Perspective Projection

  - by user1294203

  I had some trouble reconstructing position from depth sampled from the depth buffer. I use the equivalent of gluPerspective in GLM. The code in GLM is: template GLM_FUNC_QUALIFIER detail::tmat4x4 perspective ( valType const & fovy, valType const & aspect, valType const & zNear, valType const & zFar ) { valType range = tan(radians(fovy / valType(2))) * zNear; valType left = -range * aspect; valType right = range * aspect; valType bottom = -range; valType top = range; detail::tmat4x4 Result(valType(0)); Result[0][0] = (valType(2) * zNear) / (right - left); Result[1][2] = (valType(2) * zNear) / (top - bottom); Result[2][3] = - (zFar + zNear) / (zFar - zNear); Result[2][4] = - valType(1); Result[3][5] = - (valType(2) * zFar * zNear) / (zFar - zNear); return Result; } There doesn't seem to be any errors in the code. So I tried to invert the projection, the formula for the z and w coordinates after projection are: and dividing z' with w' gives the post-projective depth (which lies in the depth buffer), so I need to solve for z, which finally gives: Now, the problem is I don't get the correct position (I have compared the one reconstructed with a rendered position). I then tried using the respective formula I get by doing the same for this Matrix. The corresponding formula is: For some reason, using the above formula gives me the correct position. I really don't understand why this is the case. Have I done something wrong? Could someone enlighten me please?

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• Ray Intersecting Plane Formula in C++/DirectX

  - by user4585

  I'm developing a picking system that will use rays that intersect volumes and I'm having trouble with ray intersection versus a plane. I was able to figure out spheres fairly easily, but planes are giving me trouble. I've tried to understand various sources and get hung up on some of the variables used within their explanations. Here is a snippet of my code: bool Picking() { D3DXVECTOR3 vec; D3DXVECTOR3 vRayDir; D3DXVECTOR3 vRayOrig; D3DXVECTOR3 vROO, vROD; // vect ray obj orig, vec ray obj dir D3DXMATRIX m; D3DXMATRIX mInverse; D3DXMATRIX worldMat; // Obtain project matrix D3DXMATRIX pMatProj = CDirectXRenderer::GetInstance()->Director()->Proj(); // Obtain mouse position D3DXVECTOR3 pos = CGUIManager::GetInstance()->GUIObjectList.front().pos; // Get window width & height float w = CDirectXRenderer::GetInstance()->GetWidth(); float h = CDirectXRenderer::GetInstance()->GetHeight(); // Transform vector from screen to 3D space vec.x = (((2.0f * pos.x) / w) - 1.0f) / pMatProj._11; vec.y = -(((2.0f * pos.y) / h) - 1.0f) / pMatProj._22; vec.z = 1.0f; // Create a view inverse matrix D3DXMatrixInverse(&m, NULL, &CDirectXRenderer::GetInstance()->Director()->View()); // Determine our ray's direction vRayDir.x = vec.x * m._11 + vec.y * m._21 + vec.z * m._31; vRayDir.y = vec.x * m._12 + vec.y * m._22 + vec.z * m._32; vRayDir.z = vec.x * m._13 + vec.y * m._23 + vec.z * m._33; // Determine our ray's origin vRayOrig.x = m._41; vRayOrig.y = m._42; vRayOrig.z = m._43; D3DXMatrixIdentity(&worldMat); //worldMat = aliveActors[0]->GetTrans(); D3DXMatrixInverse(&mInverse, NULL, &worldMat); D3DXVec3TransformCoord(&vROO, &vRayOrig, &mInverse); D3DXVec3TransformNormal(&vROD, &vRayDir, &mInverse); D3DXVec3Normalize(&vROD, &vROD); When using this code I'm able to detect a ray intersection via a sphere, but I have questions when determining an intersection via a plane. First off should I be using my vRayOrig & vRayDir variables for the plane intersection tests or should I be using the new vectors that are created for use in object space? When looking at a site like this for example: http://www.tar.hu/gamealgorithms/ch22lev1sec2.html I'm curious as to what D is in the equation AX + BY + CZ + D = 0 and how does it factor in to determining a plane intersection? Any help will be appreciated, thanks.

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• Loading and drawing materials using Lib3ds

  - by Dfowj

  Hey all, i'm currently using Lib3ds to load models into my C++/OpenGL project. So far, i've been follow the model loading tutorial found here. The tutorial gives a good example of how to draw the vertices and normals using VBO's, but so far i've been lost as how to do the same thing with materials. Could i get an explanation/example of how to both load and draw materials of my meshes using Lib3ds and OpenGL?

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• Linking one uniform variable to many shaders

  - by Winged

  Let's say, that I have 3 programs, and in each of those programs there is a view matrix uniform, which should be the same in all those programs. Right now, when my camera moves, I need to re-upload the modified matrix to every program separately. Is it possible to create some kind of global uniforms which are constant for all programs linked to it, so I could just upload the matrix once? I tried creating a globalUniforms object which looked kinda like this: var globalUniforms = { program: {}, // (...) vMatrixUniform: null, // (...) initialize: function() { vMatrixUniform = gl.getUniformLocation(this.program, 'uVMatrix'); } }; So I could just link it to proper programs like this: program.vMatrixUniform = globalUniforms.vMatrixUniform;, and then pass the matrix like this: if (camera.isDirty.viewMatrix !== false) { camera.isDirty.viewMatrix = false; gl.uniformMatrix4fv(globalUniforms.vMatrixUniform, false, camera.viewMatrix.element); } but unfortunately it throws an error: Uncaught exception: gl.INVALID_VALUE was caused by call to: getUniformLocation called from line 272, column 2 in () in mysite/js/mesh.js: vMatrixUniform = gl.getUniformLocation(this.program, 'uVMatrix'); Summing up: is there a more efficient way of managing shaders which follows my logic?

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• Resources on expected behaviour when manipulating 3D objects with the mouse

  - by sebf

  Hello, In my animation editor, I have a 3D gizmo that sits on the origin of a bone; the user drags the mesh around to rotate the bone. I've found that translating the 2D movements of the mouse into sensible 3D transforms is not near as simple as i'd hoped. For example what is intuitively 'up' or 'down'? How should the magnitude of rotations change with respect to dX/dY? How to implement this? What happens when the gizmo changes position or orientation with respect to the camera? ect. So far with trial and error i've written something (very) simple that works 70% of the time. I could probably continue to hack at it until I made something that works 99% of the time, but there must be someone who needed the same thing, and spent the time coming up with a much more elegant solution. Does anyone know of one?

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