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• With 2 superposed cameras at different depths and switching their culling masks between layers to implement object-selective antialising:

  - by user36845

  We superposed two cameras, one of which uses AA as post-processing effect (AA filtering is cancelled). The camera with the AA effect has depth 0 and the camera with no effect has depth 1 as can be seen in the 5th and 6th Picture. The objects seen on the left are in layer 1 and the ones on the right are in layer 2. We then wrote a script that switches the culling masks of the cameras between the two layers at the push of buttons 1 and 2 respectively, and accomplishes object-selective antialiasing as seen in the first the three pictures. (The way two cameras separately switch culling masks between layers is illustrated in pictures 7,8 & 9.) HOWEVER, after making the environment 3D (see pictures 1-4), by parenting the 2 cameras under First-Person Controller, we started moving around in the environment and stumbled upon a big issue: When we look at the objects from such an angle as in the 4th Picture and we want to apply antialiasing to the first object (object on the left) which stands closer to our cameras now, the culling mask of 1st camera which is at depth 0, has to be switched to that object’s layer while the second object has to be in the culling mask of the 2nd camera at depth 1. And since the two image outputs of two superposed cameras are laid on top of one another; we obtain the erroneous/unrealistic result of the object farther in the back appearing closer to the camera than the front object (see 4th Picture). We already tried switching depths of cameras so that the 1st camera –with AA- now has depth 1 and the second has depth 0; BUT the camera with the AA effect Works in such a way that it applies the AA effect to its full view. So; the camera with the AA effect always has to remain at the lowest depth and the layer of the object to be antialiased has to be then assigned to the culling mask of the AA camera; otherwise all objects in the AA camera’s view (the two cubes in our case) become antialised, which we don’t want. So; how can we resolve this? The pictures are below and in the comments since each post can have 2 pics: Pic 1. No button is pushed: Both objects seem aliased. Pic 2. Button 1 is pushed: Left (1st) object is antialiased. 2nd object remains aliased. Pic 3. Button 2 is pushed: Right (2nd) object is antialiased. 1st object remains aliased. Pic 4. The problematic result in 3D, when using two superposed cameras with different depths Pic 5. Camera 1’s properties can be seen: using AA post-processing and its depth is 0 Pic 6. Camera 2’s properties can be seen: NOT using AA post-processing and its depth is 1 Pic 7. When no button is pushed, both objects are in the culling mask of Camera 2 and are aliased Pic 8. When pushed 1, camera 1 (bottom) shows the 1st object and camera 2 (top) shows the 2nd Pic 9. When pushed 2, camera 1 (bottom) shows the 2nd object and camera 2 (top) shows the 1st

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• OpenGL - Calculating camera view matrix

  - by Karle

  Problem I am calculating the model, view and projection matrices independently to be used in my shader as follows: gl_Position = projection * view * model * vec4(in_Position, 1.0); When I try to calculate my camera's view matrix the Z axis is flipped and my camera seems like it is looking backwards. My program is written in C# using the OpenTK library. Translation (Working) I've created a test scene as follows: From my understanding of the OpenGL coordinate system they are positioned correctly. The model matrix is created using: Matrix4 translation = Matrix4.CreateTranslation(modelPosition); Matrix4 model = translation; The view matrix is created using: Matrix4 translation = Matrix4.CreateTranslation(-cameraPosition); Matrix4 view = translation; Rotation (Not-Working) I now want to create the camera's rotation matrix. To do this I use the camera's right, up and forward vectors: // Hard coded example orientation: // Normally calculated from up and forward // Similar to look-at camera. Vector3 r = Vector.UnitX; Vector3 u = Vector3.UnitY; Vector3 f = -Vector3.UnitZ; Matrix4 rot = new Matrix4( r.X, r.Y, r.Z, 0, u.X, u.Y, u.Z, 0, f.X, f.Y, f.Z, 0, 0.0f, 0.0f, 0.0f, 1.0f); This results in the following matrix being created: I know that multiplying by the identity matrix would produce no rotation. This is clearly not the identity matrix and therefore will apply some rotation. I thought that because this is aligned with the OpenGL coordinate system is should produce no rotation. Is this the wrong way to calculate the rotation matrix? I then create my view matrix as: // OpenTK is row-major so the order of operations is reversed: Matrix4 view = translation * rot; Rotation almost works now but the -Z/+Z axis has been flipped, with the green cube now appearing closer to the camera. It seems like the camera is looking backwards, especially if I move it around. My goal is to store the position and orientation of all objects (including the camera) as: Vector3 position; Vector3 up; Vector3 forward; Apologies for writing such a long question and thank you in advance. I've tried following tutorials/guides from many sites but I keep ending up with something wrong. Edit: Projection Matrix Set-up Matrix4 projection = Matrix4.CreatePerspectiveFieldOfView( (float)(0.5 * Math.PI), (float)display.Width / display.Height, 0.1f, 1000.0f);

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• How to label a cuboid?

  - by usha

  Hi this is how my 3dcuboid looks, I have attached the complete code. I want to label this cuboid using different names across sides, how is this possible using opengl on android? public class MyGLRenderer implements Renderer { Context context; Cuboid rect; private float mCubeRotation; // private static float angleCube = 0; // Rotational angle in degree for cube (NEW) // private static float speedCube = -1.5f; // Rotational speed for cube (NEW) public MyGLRenderer(Context context) { rect = new Cuboid(); this.context = context; } public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glLoadIdentity(); // Reset the model-view matrix gl.glTranslatef(0.2f, 0.0f, -8.0f); // Translate right and into the screen gl.glScalef(0.8f, 0.8f, 0.8f); // Scale down (NEW) gl.glRotatef(mCubeRotation, 1.0f, 1.0f, 1.0f); // gl.glRotatef(angleCube, 1.0f, 1.0f, 1.0f); // rotate about the axis (1,1,1) (NEW) rect.draw(gl); mCubeRotation -= 0.15f; //angleCube += speedCube; } public void onSurfaceChanged(GL10 gl, int width, int height) { // TODO Auto-generated method stub if (height == 0) height = 1; // To prevent divide by zero float aspect = (float)width / height; // Set the viewport (display area) to cover the entire window gl.glViewport(0, 0, width, height); // Setup perspective projection, with aspect ratio matches viewport gl.glMatrixMode(GL10.GL_PROJECTION); // Select projection matrix gl.glLoadIdentity(); // Reset projection matrix // Use perspective projection GLU.gluPerspective(gl, 45, aspect, 0.1f, 100.f); gl.glMatrixMode(GL10.GL_MODELVIEW); // Select model-view matrix gl.glLoadIdentity(); // Reset } public void onSurfaceCreated(GL10 gl, EGLConfig config) { // TODO Auto-generated method stub gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set color's clear-value to black gl.glClearDepthf(1.0f); // Set depth's clear-value to farthest gl.glEnable(GL10.GL_DEPTH_TEST); // Enables depth-buffer for hidden surface removal gl.glDepthFunc(GL10.GL_LEQUAL); // The type of depth testing to do gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); // nice perspective view gl.glShadeModel(GL10.GL_SMOOTH); // Enable smooth shading of color gl.glDisable(GL10.GL_DITHER); // Disable dithering for better performance }} public class Cuboid{ private FloatBuffer mVertexBuffer; private FloatBuffer mColorBuffer; private ByteBuffer mIndexBuffer; private float vertices[] = { //width,height,depth -2.5f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -2.5f, 1.0f, -1.0f, -2.5f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -2.5f, 1.0f, 1.0f }; private float colors[] = { // R,G,B,A COLOR 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f }; private byte indices[] = { // VERTEX 0,1,2,3,4,5,6,7 REPRESENTATION FOR FACES 0, 4, 5, 0, 5, 1, 1, 5, 6, 1, 6, 2, 2, 6, 7, 2, 7, 3, 3, 7, 4, 3, 4, 0, 4, 7, 6, 4, 6, 5, 3, 0, 1, 3, 1, 2 }; public Cuboid() { ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); mVertexBuffer = byteBuf.asFloatBuffer(); mVertexBuffer.put(vertices); mVertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(colors.length * 4); byteBuf.order(ByteOrder.nativeOrder()); mColorBuffer = byteBuf.asFloatBuffer(); mColorBuffer.put(colors); mColorBuffer.position(0); mIndexBuffer = ByteBuffer.allocateDirect(indices.length); mIndexBuffer.put(indices); mIndexBuffer.position(0); } public void draw(GL10 gl) { gl.glFrontFace(GL10.GL_CW); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVertexBuffer); gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_COLOR_ARRAY); gl.glDrawElements(GL10.GL_TRIANGLES, 36, GL10.GL_UNSIGNED_BYTE, mIndexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_COLOR_ARRAY); } } public class Draw3drect extends Activity { private GLSurfaceView glView; // Use GLSurfaceView // Call back when the activity is started, to initialize the view @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); glView = new GLSurfaceView(this); // Allocate a GLSurfaceView glView.setRenderer(new MyGLRenderer(this)); // Use a custom renderer this.setContentView(glView); // This activity sets to GLSurfaceView } // Call back when the activity is going into the background @Override protected void onPause() { super.onPause(); glView.onPause(); } // Call back after onPause() @Override protected void onResume() { super.onResume(); glView.onResume(); } }

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• Billboarding restricted to an axis (cylindrical)

  - by user8709

  I have succesfully created a GLSL shader for a billboarding effect. I want to tweak this to restrict the billboarding to an arbitrary axis, i.e. a billboarded quad only rotates itself about the y-axis. I use the y-axis as an example, but essentially I would like this to be an arbitrary axis. Can anyone show me how to modify my existing shader below, or if I need to start from scratch, point me towards some resources that could be helpful? precision mediump float; uniform mat4 u_modelViewProjectionMat; uniform mat4 u_modelMat; uniform mat4 u_viewTransposeMat; uniform vec3 u_axis; // <------------ !!! the arbitrary axis to restrict rotation around attribute vec3 a_position0; attribute vec2 a_texCoord0; varying vec2 v_texCoord0; void main() { vec3 pos = (a_position0.x * u_viewTransposeMat[0] + a_position0.y * u_viewTransposeMat[1]).xyz; vec4 position = vec4(pos, 1.0); v_texCoord0 = a_texCoord0; gl_Position = u_modelViewProjectionMat * position; }

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• Smooth animation in Cocos2d for iOS

  - by MrDatabase

  I move a simple CCSprite around the screen of an iOS device using this code: [self schedule:@selector(update:) interval:0.0167]; - (void) update:(ccTime) delta { CGPoint currPos = self.position; currPos.x += xVelocity; currPos.y += yVelocity; self.position = currPos; } This works however the animation is not smooth. How can I improve the smoothness of my animation? My scene is exceedingly simple (just has one full-screen CCSprite with a background image and a relatively small CCSprite that moves slowly). I've logged the ccTime delta and it's not consistent (it's almost always greater than my specified interval of 0.0167... sometimes up to a factor of 4x). I've considered tailoring the motion in the update method to the delta time (larger delta = larger movement etc). However given the simplicity of my scene it's seems there's a better way (and something basic that I'm probably missing).

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• How do I detect multiple sprite collisions when there are >10 sprites?

  - by yao jiang

  I making a small program to animate the astar algorithm. If you look at the image, there are lots of yellow cars moving around. Those can collide at any moment, could be just one or all of them could just stupidly crash into each other. How do I detect all of those collisions? How do I find out which specific car has crash into which other car? I understand that pygame has collision function, but it only detects one collision at a time and I'd have to specify which sprites. Right now I am just trying to iterate through each sprite to see if there is collision: for car1 in carlist: for car2 in carlist: collide(car1, car2); This can't be the proper way to do it, if the car list goes to a huge number, a double loop will be too slow.

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• Unity: Spin wheels to move vehicle

  - by Paul Manta

  I am just getting started with Unity and I'd like to ask a question. If I have a "Vehicle" object that has two children: "FrontWheel" and "BackWheel" (both 'wheels' are cylinders), how should I set everything up such that I can move the entire vehicle by turning its wheels? When I apply a torque to "FrontWheel", the vehicle starts to move, but instead of the whole thing the moving together, the chassis is rolling on the cylinders and eventually falls off. How can I prevent it from doing that?

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• apply non-hierarchial transforms to hierarchial skeleton?

  - by user975135

  I use Blender3D, but the answer might not API-exclusive. I have some matrices I need to assign to PoseBones. The resulting pose looks fine when there is no bone hierarchy (parenting) and messed up when there is. I've uploaded an archive with sample blend of the rigged models, text animation importer and a test animation file here: http://www.2shared.com/file/5qUjmnIs/sample_files.html Import the animation by selecting an Armature and running the importer on "sba" file. Do this for both Armatures. This is how I assign the poses in the real (complex) importer: matrix_bases = ... # matrix from file animation_matrix = matrix_basis * pose.bones['mybone'].matrix.copy() pose.bones[bonename].matrix = animation_matrix If I go to edit mode, select all bones and press Alt+P to undo parenting, the Pose looks fine again. The API documentation says the PoseBone.matrix is in "object space", but it seems clear to me from these tests that they are relative to parent bones. Final 4x4 matrix after constraints and drivers are applied (object space) I tried doing something like this: matrix_basis = ... # matrix from file animation_matrix = matrix_basis * (pose.bones['mybone'].matrix.copy() * pose.bones[bonename].bone.parent.matrix_local.copy().inverted()) pose.bones[bonename].matrix = animation_matrix But it looks worse. Experimented with order of operations, no luck with all. For the record, in the old 2.4 API this worked like a charm: matrix_basis = ... # matrix from file animation_matrix = armature.bones['mybone'].matrix['ARMATURESPACE'].copy() * matrix_basis pose.bones[bonename].poseMatrix = animation_matrix pose.update() Link to Blender API ref: http://www.blender.org/documentation/blender_python_api_2_63_17/bpy.types.BlendData.html#bpy.types.BlendData http://www.blender.org/documentation/blender_python_api_2_63_17/bpy.types.PoseBone.html#bpy.types.PoseBone

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• extrapolating object state based on updates

  - by user494461

  I have a networked multi-user collaborative application. To maintain a consistent virtual world, I send updates for objects from a master peer to a guest peer. The update state contains x,y,z coordinates of object center and his rotation matrix(CHAI3d api used a 3x3 matrix) with 30Hz frequency. I want to reduce this update rate and want to send with a reduced update rate. I want a predictor on both peers. When the predicted value is outside, say a error value of 10% in comparison to master peers objects original state the master peer triggers a state update. Now for position I used velocity,position updates so that the guest peer can extrapolate position. Like velocity for position what parameter should I use for rotation extrapolition?

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• LWJGL Text Rendering

  - by Trixmix

  Currently in my project I am using LWJGL and the Slick2D library to render text onto the screen. Here is a more specific example: Font f = new Font("Times New Roman",Font.BOLD,18); font = new UnicodeFont(f); font.getEffects().add(new ColorEffect(Color.white)); font.addAsciiGlyphs(); try { font.loadGlyphs(); } catch (SlickException e) { e.printStackTrace(); } then i use font.drawString to write onto the screen. This is a quick easy way but it has a lot of disadvantages. for example font.loadGlyphs take a very long time 1-3 seconds. so when i want to change a color or font type then i have to wait 1-3 seconds which means I cannot do it while rendering (ie. cant have different color text on the same screen). My question is what is a better way of drawing multicolored text onto the screen? I use slick2d only for the text rendering so maybe i can fully get rid of the library and draw text some other way... If you have an answer please leave a quick short example. Thanks!

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• Trouble with UV Mapping Blender => Unity 3

  - by Lea Hayes

  For some reason I am getting nasty grey edges around the edges of rendered 3D models that are not present in Blender. I seem to be able to solve the problem by reducing the size of the UV coordinates within the part of the texture that is to be mapped. But this means that: I am wasting valuable texture space Loss of accuracy in drawn UV maps Could I be doing something wrong, perhaps a setting in Unity that needs changing? I have watched countless tutorials which demonstrate Blender default generated UV coordinates with "Texture Paint" which are perfectly aligned in Unity. Here is an illustration of the problem: Left: approximately 15 pixels of margin on each side of UV coordinates Right: Approximately 3 pixels of margin on each side of UV coordinates Note: Texture image resolution is 1024x1024

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• Pix for visual studio express 2012 (Desktop)

  - by JohnB

  (Originally asked on stackoverflow) Using visual c++ express 2010 for direct3d you have to download the directX sdk and there is a tool called pix for debugging shaders, looking at 3d resources etc. With visual studio 2012 express the directx sdk is included in the windows sdk that comes with it but this does not seem to include the winpix.exe tool. Is this very useful tool still available? I guess I can still use the one from the previous sdk but it seems wrong to install the entire sdk just for that tool. Is there a version for VS2012 express that I'm missing?

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• The View-Matrix and Alternative Calculations

  - by P. Avery

  I'm working on a radiosity processor in DirectX 9. The process requires that the camera be placed at the center of a mesh face and a 'screenshot' be taken facing 5 different directions...forward...up...down...left...right... ...The problem is that when the mesh face is facing up( look vector: 0, 1, 0 )...a view matrix cannot be determined using standard trigonometry functions: Matrix4 LookAt( Vector3 eye, Vector3 target, Vector3 up ) { // The "look-at" vector. Vector3 zaxis = normal(target - eye); // The "right" vector. Vector3 xaxis = normal(cross(up, zaxis)); // The "up" vector. Vector3 yaxis = cross(zaxis, xaxis); // Create a 4x4 orientation matrix from the right, up, and at vectors Matrix4 orientation = { xaxis.x, yaxis.x, zaxis.x, 0, xaxis.y, yaxis.y, zaxis.y, 0, xaxis.z, yaxis.z, zaxis.z, 0, 0, 0, 0, 1 }; // Create a 4x4 translation matrix by negating the eye position. Matrix4 translation = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, -eye.x, -eye.y, -eye.z, 1 }; // Combine the orientation and translation to compute the view matrix return ( translation * orientation ); } The above function comes from http://3dgep.com/?p=1700... ...Is there a mathematical approach to this problem? Edit: A problem occurs when setting the view matrix to up or down directions, here is an example of the problem when facing down: D3DXVECTOR4 vPos( 3, 3, 3, 1 ), vEye( 1.5, 3, 3, 1 ), vLook( 0, -1, 0, 1 ), vRight( 1, 0, 0, 1 ), vUp( 0, 0, 1, 1 ); D3DXMATRIX mV, mP; D3DXMatrixPerspectiveFovLH( &mP, D3DX_PI / 2, 1, 0.5f, 2000.0f ); D3DXMatrixIdentity( &mV ); memcpy( ( void* )&mV._11, ( void* )&vRight, sizeof( D3DXVECTOR3 ) ); memcpy( ( void* )&mV._21, ( void* )&vUp, sizeof( D3DXVECTOR3 ) ); memcpy( ( void* )&mV._31, ( void* )&vLook, sizeof( D3DXVECTOR3 ) ); memcpy( ( void* )&mV._41, ( void* )&(-vEye), sizeof( D3DXVECTOR3 ) ); D3DXVec4Transform( &vPos, &vPos, &( mV * mP ) ); Results: vPos = D3DXVECTOR3( 1.5, -6, -0.5, 0 ) - this vertex is not properly processed by shader as the homogenous w value is 0 it cannot be normalized to a position within device space...

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• How do I add shadow mapping?

  - by Jasper Creyf

  How do I add shadow mapping? I don't care if it uses GLSL it just has to work. I have been searching on stencil shadows and shadow mapping, all the examples given did nothing, if you don't understand that it means not even a single shadow is even being rendered. If you know how to add stencil shadows or shadow mapping, then please show some java code and if you're using GLSL then please show the code for them too.

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• XNA - Render texture to a rendertarget 2d via SpriteBatch error

  - by Jared B

  I got simple code that uses SpriteBatch to draw a texture onto a RenderTarget2D... private void drawScene(GameTime g) { GraphicsDevice.Clear(skyColor); GraphicsDevice.SetRenderTarget(targetScene); drawSunAndMoon(); effect.Fog = true; GraphicsDevice.SetVertexBuffer(line); effect.MainEffect.CurrentTechnique.Passes[0].Apply(); GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleStrip, 0, 2); GraphicsDevice.SetRenderTarget(null); SceneTexture = targetScene; } private void drawPostProcessing(GameTime g) { effect.SceneTexture = SceneTexture; GraphicsDevice.SetRenderTarget(targetBloom); spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.Opaque, null, null, null); { if(Bloom) effect.BlurEffect.CurrentTechnique.Passes[0].Apply(); spriteBatch.Draw(targetScene, new Rectangle(0, 0, Window.ClientBounds.Width, Window.ClientBounds.Height), Color.White); } spriteBatch.End(); BloomTexture = targetBloom; GraphicsDevice.SetRenderTarget(null); } Both methods are called from Draw(GameTime gameTime). First drawScene is called, then drawPostProcessing is called. The thing is, I can't run the code because "the render target must not be set on the device when it is used as a texture." at line spriteBatch.Draw(targetScene, new Rectangle(0, 0, Window.ClientBounds.Width, Window.ClientBounds.Height), Color.White); I already found the solution, which is to draw the actual renderTarget (targetScene) to the texture so it doesn't create a reference to the loaded rendertarget. However, to my knowledge, the only way of doing this is to write: GraphicsDevice.SetRenderTarget(OutputTarget) SpriteBatch.Draw(InputTarget, ...) GraphicsDevice.SetRenderTarget(null) Which encounters the same exact problem I'm having right now. So, the question I'm asking is: how would I render InputTarget to OutputTarget without reference issues?

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• Platformer gravity where gravity is greater than tile size

  - by Sara

  I am making a simple grid-tile-based platformer with basic physics. I have 16px tiles, and after playing with gravity it seems that to get a nice quick Mario-like jump feel, the player ends up moving faster than 16px per second at the ground. The problem is that they clip through the first layer of tiles before collisions being detected. Then when I move the player to the top of the colliding tile, they move to the bottom-most tile. I have tried limiting their maximum velocity to be less than 16px but it does not look right. Are there any standard approaches to solving this? Thanks.

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• How to properly render a Frame Buffer to the BackBuffer in Stage3D / AGAL

  - by bigp

  After doing a render pass with RenderToTarget (RTT), how do you properly render that texture buffer to the screen while maintaining original scale / proportions so it doesn't stretch or lose quality? Can an AGAL VertexShader & FragmentShader be written so it's adaptable to any Texture size and Viewport dimensions? I find I'm getting some "blocky" effects in some of my first attempts at "ping-ponging" between two Texture buffers (to create trailing effects). Perhaps I'm not using the UVs correctly between the rendering-to-target and/or the backbuffer? Is there a simpler way just to "splash" the texture on the backbuffer, or is a Quad absolutely necessary (4 vertices, 2 triangles)? If it needs the Quad, should the Texture buffer be fully drawn (0.0 to 1.0 for vertical and horizontal UVs), or only a percentage of it should, like the example below? Texture Buffer U: 0.0 to viewport.width/texturebuffer.width; Texture Buffer V: 0.0 to viewport.height/texturebuffer.height; Thanks!

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• Understanding normal maps on terrain

  - by JohnB

  I'm having trouble understanding some of the math behind normal map textures even though I've got it to work using borrowed code, I want to understand it. I have a terrain based on a heightmap. I'm generating a mesh of triangles at load time and rendering that mesh. Now for each vertex I need to calculate a normal, a tangent, and a bitangent. My understanding is as follows, have I got this right? normal is a unit vector facing outwards from the surface of the triangle. For a vertex I take the average of the normals of the triangles using that vertex. tangent is a unit vector in the direction of the 'u' coordinates of the texture map. As my texture u,v coordinates follow the x and y coordinates of the terrain, then my understanding is that this vector is simply the vector along the surface in the x direction. So should be able to calculate this as simply the difference between vertices in the x direction to get a vector, (and normalize it). bitangent is a unit vector in the direction of the 'v' coordinates of the texture map. As my texture u,v coordinates follow the x and y coordinates of the terrain, then my understanding is that this vector is simply the vector along the surface in the y direction. So should be able to calculate this as simply the difference between vertices in the y direction to get a vector, (and normalize it). However the code I have borrowed seems much more complicated than this and takes into account the actual values of u, and v at each vertex which I don't understand the need for as they increase in exactly the same direction as x, and y. I implemented what I thought from above, and it simply doesn't work, the normals are clearly not working for lighting. Have I misunderstood something? Or can someone explain to me the physical meaning of the tangent and bitangent vectors when applied to a mesh generated from a hightmap like this, when u and v texture coordinates map along the x and y directions. Thanks for any help understanding this.

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• Renderbuffer to GLSL shader?

  - by Dan

  I have a software that performs volume rendering through a raycasting approach. The actual raycasting shader writes the raycasted volume depth into a framebuffer object, through gl_FragDepth, that I bind before calling the shader. The problem I have is that I would like to use this depth in another shader that I call later on. I figured out that the only way to do that is to bind the framebuffer once the raycasting has finished, read the depthmap through something like glReadPixels(0, 0, m_winSize.x , m_winSize.y, GL_DEPTH_COMPONENT, GL_FLOAT, pixels); and write it to a 2D texture as usual glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, m_winSize.x, m_winSize.y, 0, GL_DEPTH_COMPONENT, GL_FLOAT, pixels) and then pass this 2D texture that contains a simple depth map to the other shader. However, I am not entirely sure that what I do is the proper way to do this. Is there anyway to pass the framebuffer that I fill up in my raycasting shader to the other shader?

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• Low-level GPU code and Shader Compilation

  - by ktodisco

  Bear with me, because I will raise several questions at once. I still feel, though, that overall this can be treated as one question that may be answered succinctly. I recently dove into solidifying my understanding of the assembly language, low-level memory operations, CPU structure, and program optimizations. This also sparked my interest in how higher-level shading languages, GLSL and HLSL in particular, are compiled and optimized, as well as what formats they are reduced to before machine code is generated (assuming they are not converted directly into machine code). After a bit of research into this, the best resource I've found is this presentation from ATI about the compilation of and optimizations for HLSL. I also found sample ARB assembly code. This sort of addressed my original curiosity, but it raised several other questions. The assembler code in the ATI presentation seems like it contains instructions specifically targeted for the GPU, but is this merely a hypothetical example created for the purpose of conceptual understanding, or is this code really generated during shader compilation? If so, is it possible to inspect it, or even write it in place of the higher-level syntax? My initial searches for an answer to the last question tell me that this may be disallowed, but I have not dug too deep yet. Also, along the same lines, are GLSL shader programs compiled into ARB assembly code before machine code is generated, and is it possible to write direct ARB assembly? Lastly, and perhaps what I am most interested in finding out: are there comprehensive resources on shader compilation and low-level GPU code? I have been unable to find any thus far. I ask simply because I am curious :)

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• How to do reflective collisions with particles hitting background tiles?

  - by Shawn LeBlanc

  In my 2d pixel old-school platformer, I'm looking for methods for bouncing particles off of background tiles. Particles aren't affected by gravity and collisions are "reflective". By that I mean a particle hitting the side of a square tile at 45 degrees should bounce off at 45 degrees as well. We can assume that tiles will always be perfectly square. No slopes or anything. What are efficient methods and algorithms to do this? I'd be implementing this on a Sega Genesis.

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• xna orbit camera troubles

  - by user17753

  I have a Model named cube to which I load in LoadContent(): cube = Content.Load<Model>("untitled");. In the Draw Method I call DrawModel: private void DrawModel(Model m, Matrix world) { foreach (ModelMesh mesh in m.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.View = camera.View; effect.Projection = camera.Projection; effect.World = world; } mesh.Draw(); } } camera is of the Camera type, a class I've setup. Right now it is instantiated in the initialization section with the graphics aspect ratio and the translation (world) vector of the model, and the Draw loop calls the camera.UpdateCamera(); before drawing the models. class Camera { #region Fields private Matrix view; // View Matrix for Camera private Matrix projection; // Projection Matrix for Camera private Vector3 position; // Position of Camera private Vector3 target; // Point camera is "aimed" at private float aspectRatio; //Aspect Ratio for projection private float speed; //Speed of camera private Vector3 camup = Vector3.Up; #endregion #region Accessors /// <summary> /// View Matrix of the Camera -- Read Only /// </summary> public Matrix View { get { return view; } } /// <summary> /// Projection Matrix of the Camera -- Read Only /// </summary> public Matrix Projection { get { return projection; } } #endregion /// <summary> /// Creates a new Camera. /// </summary> /// <param name="AspectRatio">Aspect Ratio to use for the projection.</param> /// <param name="Position">Target coord to aim camera at.</param> public Camera(float AspectRatio, Vector3 Target) { target = Target; aspectRatio = AspectRatio; ResetCamera(); } private void Rotate(Vector3 Axis, float Amount) { position = Vector3.Transform(position - target, Matrix.CreateFromAxisAngle(Axis, Amount)) + target; } /// <summary> /// Resets Default Values of the Camera /// </summary> private void ResetCamera() { speed = 0.05f; position = target + new Vector3(0f, 20f, 20f); projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, aspectRatio, 0.5f, 100f); CalculateViewMatrix(); } /// <summary> /// Updates the Camera. Should be first thing done in Draw loop /// </summary> public void UpdateCamera() { Rotate(Vector3.Right, speed); CalculateViewMatrix(); } /// <summary> /// Calculates the View Matrix for the camera /// </summary> private void CalculateViewMatrix() { view = Matrix.CreateLookAt(position,target, camup); } I'm trying to create the camera so that it can orbit the center of the model. For a test I am calling Rotate(Vector3.Right, speed); but it rotates almost right but gets to a point where it "flips." If I rotate along a different axis Rotate(Vector3.Up, speed); everything seems OK in that direction. So I guess, can someone tell me what I'm not accounting for in the above code I wrote? Or point me to an example of an orbiting camera that can be fixed on an arbitrary point?

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• GLSL: How Do I cast a float into an int?

  - by dugla

  In a GLSL fragment shader I am trying to cast a float into an int. The compiler has other ideas. It complains thusly: ERROR: 0:60: '=' : cannot convert from 'mediump float' to 'highp int' I am trying to do this: mediump float indexf = floor(2.0 * mixer); highp int index = indexf; I (vainly) tried to raise the precision of the int above the float to appease the GL Gods but no joy. Could someone please school me here? Thanks, Doug

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• XNA - Error while rendering a texture to a 2D render target via SpriteBatch

  - by Jared B

  I've got this simple code that uses SpriteBatch to draw a texture onto a RenderTarget2D: private void drawScene(GameTime g) { GraphicsDevice.Clear(skyColor); GraphicsDevice.SetRenderTarget(targetScene); drawSunAndMoon(); effect.Fog = true; GraphicsDevice.SetVertexBuffer(line); effect.MainEffect.CurrentTechnique.Passes[0].Apply(); GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleStrip, 0, 2); GraphicsDevice.SetRenderTarget(null); SceneTexture = targetScene; } private void drawPostProcessing(GameTime g) { effect.SceneTexture = SceneTexture; GraphicsDevice.SetRenderTarget(targetBloom); spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.Opaque, null, null, null); { if (Bloom) effect.BlurEffect.CurrentTechnique.Passes[0].Apply(); spriteBatch.Draw( targetScene, new Rectangle(0, 0, Window.ClientBounds.Width, Window.ClientBounds.Height), Color.White); } spriteBatch.End(); BloomTexture = targetBloom; GraphicsDevice.SetRenderTarget(null); } Both methods are called from my Draw(GameTime gameTime) function. First drawScene is called, then drawPostProcessing is called. The thing is, when I run this code I get an error on the spriteBatch.Draw call: The render target must not be set on the device when it is used as a texture. I already found the solution, which is to draw the actual render target (targetScene) to the texture so it doesn't create a reference to the loaded render target. However, to my knowledge, the only way of doing this is to write: GraphicsDevice.SetRenderTarget(outputTarget) SpriteBatch.Draw(inputTarget, ...) GraphicsDevice.SetRenderTarget(null) Which encounters the same exact problem I'm having right now. So, the question I'm asking is: how would I render inputTarget to outputTarget without reference issues?

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• Circular Bullet Spread not Even

  - by SoulBeaver

  I'm creating a bullet shooter much in the style of Touhou. Right now I want to have a very simple circular shot being fired from the enemy. See this picture: As you can see, the spacing is very uneven, which isn't very good if you want to survive. The code I'm using is this: private function shoot() : void { const BULLETS_PER_WAVE : int = 72; var interval : Number = BULLETS_PER_WAVE / 360; for (var i : int = 0; i < BULLETS_PER_WAVE; ++i { var xSpeed : Number = GameConstants.BULLET_NORMAL_SPEED_X * Math.sin(i * interval); var ySpeed : Number = GameConstants.BULLET_NORMAL_SPEED_Y * Math.cos(i * interval); BulletFactory.createNormalBullet(bulletColor_, alice_.center, xSpeed, ySpeed); } canShoot_ = false; cooldownTimer_.start(); } I imagine my mistake is in the sin, cos functions, but I'm not entirely sure what's wrong.

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