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• Timestep schemes for physics simulations

  - by ktodisco

  The operations used for stepping a physics simulation are most commonly: Integrate velocity and position Collision detection and resolution Contact resolution (in advanced cases) A while ago I came across this paper from Stanford that proposed an alternative scheme, which is as follows: Collision detection and resolution Integrate velocity Contact resolution Integrate position It's intriguing because it allows for robust solutions to the stacking problem. So it got me wondering... What, if any, alternative schemes are available, either simple or complex? What are their benefits, drawbacks, and performance considerations?

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• Drawing a circle in opengl es android, squiggly boundaries

  - by ladiesMan217

  I am new to OpenGL ES and facing a hard time drawing a circle on my GLSurfaceView. Here's what I have so far. the Circle Class public class MyGLBall { private int points=40; private float vertices[]={0.0f,0.0f,0.0f}; private FloatBuffer vertBuff; //centre of circle public MyGLBall(){ vertices=new float[(points+1)*3]; for(int i=3;i<(points+1)*3;i+=3){ double rad=(i*360/points*3)*(3.14/180); vertices[i]=(float)Math.cos(rad); vertices[i+1]=(float) Math.sin(rad); vertices[i+2]=0; } ByteBuffer bBuff=ByteBuffer.allocateDirect(vertices.length*4); bBuff.order(ByteOrder.nativeOrder()); vertBuff=bBuff.asFloatBuffer(); vertBuff.put(vertices); vertBuff.position(0); } public void draw(GL10 gl){ gl.glPushMatrix(); gl.glTranslatef(0, 0, 0); // gl.glScalef(size, size, 1.0f); gl.glColor4f(1.0f,1.0f,1.0f, 1.0f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuff); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points/2); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glPopMatrix(); } } I couldn't retrieve the screenshot of my image but here's what it looks like As you can see the border has crests and troughs thereby renering it squiggly which I do not want. All I want is a simple curve

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• Adding Vertices to a dynamic mesh via Method Call

  - by Raven Dreamer

  I have a C# Struct with a static method, "Get Shape" which populates a List with the vertices of a polyhedron. Method Signature: public static void GetShape(Block b, int x, int y, int z, List<Vector3> vertices, List<int> triangles, List<Vector2> uvs, List<Vector2> uv2s) Adding directly to the vertices list (via vertices.Add(vector3) ), the code works as expected, and the new polyhedron appears when I trigger the method. However, I want to do some processing on the vertices I'm adding (a rotation), and the most sensible way I can think to do that is by creating a separate list of Vector3s, and then combining the lists when I'm done. However, vertices.AddRange(newVerts) does not add the shape to the mesh, nor does a foreach loop with verts.Add(vertices[i]). And this is before I've added in any of the processing! I have a feeling this might stem from passing the list of vertices in as a parameter, rather than returning a list and then adding to the vertices in the calling object, but since I'm filling 4 lists, I was trying to avoid having to create a data struct to return all four at once. Any ideas? The working version of the method is reprinted below, in full: public static void GetShape(Block b, int x, int y, int z, List<Vector3> vertices, List<int> triangles, List<Vector2> uvs, List<Vector2> uv2s) { //List<Vector3> vertices = new List<Vector3>(); int l_blockShape = b.blockShape; int l_blockType = b.blockType; //CheckFace checks if the block is empty //if this block is empty, don't draw anything. int vertexIndex; //only y faces need to be hidden. //if((l_blockShape & BlockShape.NegZFace) == BlockShape.NegZFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.2f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.8f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.8f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.2f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //XY Z+1 face //if((l_blockShape & BlockShape.PosZFace) == BlockShape.PosZFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.2f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.2f, y , z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.8f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZY face //if((l_blockShape & BlockShape.NegXFace) == BlockShape.NegXFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.2f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.2f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.8f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZY X+1 face // if((l_blockShape & BlockShape.PosXFace) == BlockShape.PosXFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y + 1, z+.2f)); vertices.Add(new Vector3(x+.8f, y + 1, z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.2f)); // first triangle for the face triangles.Add(vertexIndex); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+3); // second triangle for the face triangles.Add(vertexIndex+1); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+3); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZX face if((l_blockShape & BlockShape.NegYFace) == BlockShape.NegYFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y , z+.8f)); vertices.Add(new Vector3(x+.8f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.2f)); vertices.Add(new Vector3(x+.2f, y , z+.8f)); // first triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex); // second triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+1); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } //ZX + 1 face if((l_blockShape & BlockShape.PosYFace) == BlockShape.PosYFace) { vertexIndex = vertices.Count; //top left, top right, bottom right, bottom left vertices.Add(new Vector3(x+.8f, y+1 , z+.2f)); vertices.Add(new Vector3(x+.8f, y+1 , z+.8f)); vertices.Add(new Vector3(x+.2f, y+1 , z+.8f)); vertices.Add(new Vector3(x+.2f, y+1 , z+.2f)); // first triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+1); triangles.Add(vertexIndex); // second triangle for the face triangles.Add(vertexIndex+3); triangles.Add(vertexIndex+2); triangles.Add(vertexIndex+1); //UVs for the face uvs.Add( new Vector2(0,1)); uvs.Add( new Vector2(1,1)); uvs.Add( new Vector2(1,0)); uvs.Add( new Vector2(0,0)); //UV2s (lightmapping?) uv2s.Add( new Vector2(0,1)); uv2s.Add( new Vector2(1,1)); uv2s.Add( new Vector2(1,0)); uv2s.Add( new Vector2(0,0)); } }

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• [JOGL] My program is too slow, how can I profile with Eclipse?

  - by nkint

  My simple opengl program is really toooo slow and not fluid. I'm rendering 30 sphere with simple illumination and simple materials. The only complex computing stuff I do is a collision detection between ray-mouse and spheres (that works ok and i do it only in mouseMoved) I'm not using any threads, just an animator to move spheres. How can I profile my jogl project? Or maybe (most probable...) I have some opengl instructions that I don't understand and make render particular accurate (or back face rendering that I don't need or whatever I don't know exactly I'm just entering the opengl world)

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• Decal implementation

  - by dreta

  I had issues finding information about decals, so maybe this question will help others. The implementation is for a forward renderer. Could somebody confirm if i got decal implementation right? You define a cube of any dimension that'll define the projection volume in common space. You check for triangle intersection with the defined cube to recieve triangles that the projection will affect. You clip these triangles and save them. You then use matrix tricks to calculate UV coordinates for the saved triangles that'll reference the texture you're projecting. To do this you take the vectors representing height, width and depth of the cube in common space, so that f.e. the bottom left corner is the origin. You put that in a matrix as the i, j, k unit vectors, set the translation for the cube, then you inverse this matrix. You multiply the vertices of the saved triangles by this matrix, that way you get their coordinates inside of a 0 to 1 size cube that you use as the UV coordinates. This way you have the original triangles you're projecting onto and you have UV coordinates for them (the UV coordinates are referencing the texture you're projecting). Then you rerender the saved triangles onto the scene and they overwrite the area of projection with the projected image. Now the questions that i couldn't find answers for. Is the last point right? I've never done software clipping, but it seems error prone enough, due to limited precision, that the'll be some z fighting occuring for the projected texture. Also is the way of getting UV coordinates correct?

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• Something other than Vertex Welding with Texture Atlas?

  - by Tim Winter

  What options (in C# with XNA) would there be for texture usage in a procedural generated 3D world made of cubes to increase performance? Yes, it's like Minecraft. I've been doing a texture atlas and rendering faces individually (4 vertices per face), but I've also read in a couple places about using texture wrapping with two 1D atlases to merge adjacent faces with the same texture. If two or more adjacent faces share the same image, it'd be quite easy to wrap in this way reducing vertices by a large amount. My problem with this is having too many textures, swapping too often, and many image related things like non-power of 2 images. Is there a middle ground option between the 1D texture atlas trick and rendering 4 vertices per cube face? This is a picture of what I have currently (in wireframe). 4 vertices per face seems extremely inefficient to me.

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• Clipping polygons in XNA with stencil (not using spritebatch)

  - by Blau

  The problem... i'm drawing polygons, in this case boxes, and i want clip children polygons with its parent's client area. // Class Region public void Render(GraphicsDevice Device, Camera Camera) { int StencilLevel = 0; Device.Clear( ClearOptions.Stencil, Vector4.Zero, 0, StencilLevel ); Render( Device, Camera, StencilLevel ); } private void Render(GraphicsDevice Device, Camera Camera, int StencilLevel) { Device.SamplerStates[0] = this.SamplerState; Device.Textures[0] = this.Texture; Device.RasterizerState = RasterizerState.CullNone; Device.BlendState = BlendState.AlphaBlend; Device.DepthStencilState = DepthStencilState.Default; Effect.Prepare(this, Camera ); Device.DepthStencilState = GlobalContext.GraphicsStates.IncMask; Device.ReferenceStencil = StencilLevel; foreach ( EffectPass pass in Effect.Techniques[Technique].Passes ) { pass.Apply( ); Device.DrawUserIndexedPrimitives<VertexPositionColorTexture>( PrimitiveType.TriangleList, VertexData, 0, VertexData.Length, IndexData, 0, PrimitiveCount ); } foreach ( Region child in ChildrenRegions ) { child.Render( Device, Camera, StencilLevel + 1 ); } Effect.Prepare( this, Camera ); // This does not works Device.BlendState = GlobalContext.GraphicsStates.NoWriteColor; Device.DepthStencilState = GlobalContext.GraphicsStates.DecMask; Device.ReferenceStencil = StencilLevel; // This should be +1, but in that case the last drrawed is blue and overlap all foreach ( EffectPass pass in Effect.Techniques[Technique].Passes ) { pass.Apply( ); Device.DrawUserIndexedPrimitives<VertexPositionColorTexture>( PrimitiveType.TriangleList, VertexData, 0, VertexData.Length, IndexData, 0, PrimitiveCount ); } } public static class GraphicsStates { public static BlendState NoWriteColor = new BlendState( ) { ColorSourceBlend = Blend.One, AlphaSourceBlend = Blend.One, ColorDestinationBlend = Blend.InverseSourceAlpha, AlphaDestinationBlend = Blend.InverseSourceAlpha, ColorWriteChannels1 = ColorWriteChannels.None }; public static DepthStencilState IncMask = new DepthStencilState( ) { StencilEnable = true, StencilFunction = CompareFunction.Equal, StencilPass = StencilOperation.IncrementSaturation, }; public static DepthStencilState DecMask = new DepthStencilState( ) { StencilEnable = true, StencilFunction = CompareFunction.Equal, StencilPass = StencilOperation.DecrementSaturation, }; } How can achieve this? EDIT: I've just relized that the NoWriteColors.ColorWriteChannels1 should be NoWriteColors.ColorWriteChannels. :) Now it's clipping right. Any other approach?

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• How much it will cost to create tile-set similar to HoM&M 2?

  - by Alexey Petrushin

  How much it will cost to create tile-set similar to HoM&M 2? I'm mostly interested in the tile-set graphics only, no animation needed, the big images of town and creatures can be done as quick and dirty pensil sketches. The quality of tiles and its amount should be roughly the same as in HoM&M 2. Can You please give a rough estimate how much it will take man-hours and how much will it cost?

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• as3 3D camera lookat

  - by Johannes Jensen

  I'm making a 3D camera scene in Flash, draw using drawTriangles() and rotated and translated using a Matrix3D. I've got the camera to look after a specific point, but only on the Y-axis, using the x and z coordinates, here is my code so far: var dx:Number = camera.x - lookAt.x; var dy:Number = camera.y - lookAt.y; var dz:Number = camera.z - lookAt.z; camera.rotationY = Math.atan2(dz, dx) * (180 / Math.PI) + 270; so no matter the x or z position, the point is always on the mid of the screen, IF and only if y matches with the camera. So what I need is to calculate the rotationX (which are measured in degrees not radians), and I was wondering how I would do this?

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• SlimDX and Parsing .X Files

  - by P. Avery

  I'm trying to parse a .x file using SlimDX. I can create the XFile object and register templates but I'm having problems with the enumeration object. The enumeration object has a child count of 0 for a file I know to have valid data. Here is code to create file, enumeration, and data objects: public void Parse(string filename, string templates, ref Frame aParam) { XFile xfile = null; XFileEnumerationObject enumObj = null; XFileData dataObj = null; // create file object xfile = new XFile(); // register templates if (xfile.RegisterTemplates(XFile.DefaultTemplates).IsFailure) { Console.WriteLine(Result.Last); xfile.Dispose(); return; } // create enumeration object enumObj = xfile.CreateEnumerationObject(filename, System.Runtime.InteropServices.CharSet.Auto); if (enumObj == null) { xfile.Dispose(); return; } // get child count( returns 0 here ) long ncElements = enumObj.ChildCount; for (int i = 0; i < ncElements; ++i) { // never reached... dataObj = enumObj.GetChild(i); if (dataObj.IsReference) continue; try { Parse(dataObj, ref aParam); } catch (Exception e) { e.Write(); } finally { dataObj.Dispose(); } } enumObj.Dispose(); xfile.Dispose(); } ...There are no exceptions thrown by this function...the child count is 0 so the conditional loop breaks right away, the file objects are disposed of and the function returns... Here is .x file...a simple cube: xof 0303txt 0032 Frame Root { FrameTransformMatrix { 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000;; } Frame Cube { FrameTransformMatrix { 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 0.000000, 1.000000;; } Mesh Cube{ //Cube Mesh 36; -1.000000; 1.000000; 1.000000;, -1.000000;-1.000000; 1.000000;, 0.999999;-1.000001; 1.000000;, -1.000000;-1.000000;-1.000000;, 1.000000;-1.000000;-1.000000;, 0.999999;-1.000001; 1.000000;, 1.000000; 0.999999; 1.000000;, -1.000000; 1.000000; 1.000000;, 0.999999;-1.000001; 1.000000;, -1.000000; 1.000000;-1.000000;, -1.000000;-1.000000;-1.000000;, -1.000000; 1.000000; 1.000000;, -1.000000; 1.000000; 1.000000;, 1.000000; 0.999999; 1.000000;, 1.000000; 1.000000;-1.000000;, 1.000000; 0.999999; 1.000000;, 0.999999;-1.000001; 1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000;-1.000000;-1.000000;, -1.000000;-1.000000; 1.000000;, -1.000000; 1.000000; 1.000000;, 1.000000; 1.000000;-1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000; 1.000000;-1.000000;, 1.000000; 1.000000;-1.000000;, 1.000000; 0.999999; 1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000; 1.000000;-1.000000;, -1.000000; 1.000000; 1.000000;, 1.000000; 1.000000;-1.000000;, -1.000000;-1.000000; 1.000000;, -1.000000;-1.000000;-1.000000;, 0.999999;-1.000001; 1.000000;, 1.000000;-1.000000;-1.000000;, -1.000000;-1.000000;-1.000000;, -1.000000; 1.000000;-1.000000;; 12; 3;0;1;2;, 3;3;4;5;, 3;6;7;8;, 3;9;10;11;, 3;12;13;14;, 3;15;16;17;, 3;18;19;20;, 3;21;22;23;, 3;24;25;26;, 3;27;28;29;, 3;30;31;32;, 3;33;34;35;; MeshNormals { //Mesh Normals 36; 0.000000;-0.000000; 1.000000;, 0.000000;-0.000000; 1.000000;, 0.000000;-0.000000; 1.000000;, -0.000000;-1.000000;-0.000000;, -0.000000;-1.000000;-0.000000;, -0.000000;-1.000000;-0.000000;, -0.000000;-0.000000; 1.000000;, -0.000000;-0.000000; 1.000000;, -0.000000;-0.000000; 1.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, 1.000000;-0.000001; 0.000000;, 1.000000;-0.000001; 0.000000;, 1.000000;-0.000001; 0.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, -1.000000; 0.000000;-0.000000;, 0.000000; 0.000000;-1.000000;, 0.000000; 0.000000;-1.000000;, 0.000000; 0.000000;-1.000000;, 1.000000; 0.000000;-0.000000;, 1.000000; 0.000000;-0.000000;, 1.000000; 0.000000;-0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, 0.000000; 1.000000; 0.000000;, -0.000000;-1.000000; 0.000000;, -0.000000;-1.000000; 0.000000;, -0.000000;-1.000000; 0.000000;, 0.000000;-0.000000;-1.000000;, 0.000000;-0.000000;-1.000000;, 0.000000;-0.000000;-1.000000;; 12; 3;0;1;2;, 3;3;4;5;, 3;6;7;8;, 3;9;10;11;, 3;12;13;14;, 3;15;16;17;, 3;18;19;20;, 3;21;22;23;, 3;24;25;26;, 3;27;28;29;, 3;30;31;32;, 3;33;34;35;; } //End of Mesh Normals MeshMaterialList { //Mesh Material List 1; 12; 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;; Material Material { 0.640000; 0.640000; 0.640000; 1.000000;; 96.078431; 0.500000; 0.500000; 0.500000;; 0.000000; 0.000000; 0.000000;; TextureFilename {"Yellow.jpg";} } } //End of Mesh Material List MeshTextureCoords UVMap{ //Mesh UV Coordinates 36; 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 0.000000;, 0.000000; 1.000000;, 1.000000; 1.000000;, 1.000000; 0.000000;; } //End of Mesh UV Coordinates } //End of Mesh Mesh } //End of Cube } //End of Root Frame

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• Pygame surfaces and their Rects

  - by Jaka Novak

  I am trying to understand how pygame surfaces work. I am confused about Rect position of Surface object. If I try blit surface on screen at some position then Surface is drawn at right position, but Rect of the surface is still at position (0, 0)... I tried write my own surface class with new rect, but i am not sure if is that right solution. My goal is that i could move surface like image with rect.move() or something like that. If there is any solution to do that i would be happy to read it. Thanks for answer and time for reading this awful English If helps i write some code for better understanding my problem. (run it first, and then uncomment two lines of code and run again to see the diference): import pygame from pygame.locals import * class SurfaceR(pygame.Surface): def __init__(self, size, position): pygame.Surface.__init__(self, size) self.rect = pygame.Rect(position, size) self.position = position self.size = size def get_rect(self): return self.rect def main(): pygame.init() screen = pygame.display.set_mode((640, 480)) pygame.display.set_caption("Screen!?") clock = pygame.time.Clock() fps = 30 white = (255, 255, 255) red = (255, 0, 0) green = (0, 255, 0) blue = (0, 0, 255) surface = pygame.Surface((70,200)) surface.fill(red) surface_re = SurfaceR((300, 50), (100, 300)) surface_re.fill(blue) while True: for event in pygame.event.get(): if event.type == QUIT: return 0 screen.blit(surface, (100,50)) screen.blit(surface_re, surface_re.position) #pygame.draw.rect(screen, white, surface.get_rect()) #pygame.draw.rect(screen, white, surface_re.get_rect()) pygame.display.update() clock.tick(fps) if __name__ == "__main__": main()

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• Quaternion Camera

  - by Alex_Hyzer_Kenoyer

  Can someone help me figure out how to use a Quaternion with the PerspectiveCamera in libGDX or in general? I am trying to rotate my camera around a sphere that is being drawn at (0,0,0). I am not sure how to go about setting up the quaternion correctly, manipulating it, and then applying it to the camera. Edit: Here is what I have tried to do so far. // This is how I set it up Quaternion orientation = new Quaternion(); orientation.setFromAxis(Vector3.Y, 45); // This is how I am trying to update the rotations public void rotateX(float amount) { Quaternion temp = new Quaternion(); temp.set(Vector3.X, amount); orientation.mul(temp); } public void rotateY(float amount) { Quaternion temp = new Quaternion(); temp.set(Vector3.Y, amount); orientation.mul(temp); } public void updateCamera() { // This is where I am unsure how to apply the rotations to the camera // I think I should update the view and projection matrices? camera.view.mul(orientation); ... }

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• Atmospheric scattering sky from space artifacts

  - by ollipekka

  I am in the process of implementing atmospheric scattering of a planets from space. I have been using Sean O'Neil's shaders from http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter16.html as a starting point. I have pretty much the same problem related to fCameraAngle except with SkyFromSpace shader as opposed to GroundFromSpace shader as here: http://www.gamedev.net/topic/621187-sean-oneils-atmospheric-scattering/ I get strange artifacts with sky from space shader when not using fCameraAngle = 1 in the inner loop. What is the cause of these artifacts? The artifacts disappear when fCameraAngle is limtied to 1. I also seem to lack the hue that is present in O'Neil's sandbox (http://sponeil.net/downloads.htm) Camera position X=0, Y=0, Z=500. GroundFromSpace on the left, SkyFromSpace on the right. Camera position X=500, Y=500, Z=500. GroundFromSpace on the left, SkyFromSpace on the right. I've found that the camera angle seems to handled very differently depending the source: In the original shaders the camera angle in SkyFromSpaceShader is calculated as: float fCameraAngle = dot(v3Ray, v3SamplePoint) / fHeight; Whereas in ground from space shader the camera angle is calculated as: float fCameraAngle = dot(-v3Ray, v3Pos) / length(v3Pos); However, various sources online tinker with negating the ray. Why is this? Here is a C# Windows.Forms project that demonstrates the problem and that I've used to generate the images: https://github.com/ollipekka/AtmosphericScatteringTest/ Update: I have found out from the ScatterCPU project found on O'Neil's site that the camera ray is negated when the camera is above the point being shaded so that the scattering is calculated from point to the camera. Changing the ray direction indeed does remove artifacts, but introduces other problems as illustrated here: Furthermore, in the ScatterCPU project, O'Neil guards against situations where optical depth for light is less than zero: float fLightDepth = Scale(fLightAngle, fScaleDepth); if (fLightDepth < float.Epsilon) { continue; } As pointed out in the comments, along with these new artifacts this still leaves the question, what is wrong with the images where camera is positioned at 500, 500, 500? It feels like the halo is focused on completely wrong part of the planet. One would expect that the light would be closer to the spot where the sun should hits the planet, rather than where it changes from day to night. The github project has been updated to reflect changes in this update.

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• Sprite sheets, Clamp or Wrap?

  - by David

  I'm using a combination of sprite sheets for well, sprites and individual textures for infinite tiling. For the tiling textures I'm obviously using Wrap to draw the entire surface in one call but up until now I've been making a seperate batch using Clamp for drawing sprites from the sprite sheets. The sprite sheets include a border (repeating the edge pixels of each sprite) and my code uses the correct source coordinates for sprites. But since I'm never giving coordinates outside of the texture when drawing sprites (and indeed the border exists to prevent bleed over when filtering) it's struck me that I'd be better off just using Wrap so that I can combine everything into one batch. I just want to be sure that I haven't overlooked something obvious. Is there any reason that Wrap would be harmful when used with a sprite sheet?

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• Calculate the Intersection of Two Volumes

  - by igrad

  If you've ever played The Swapper, you'll have a good idea of what I'm asking about. I need to check for, and isolate, areas of a rectangle that may intersect with either a circle or another rectangle. These selected areas will receive special properties, and the areas will be non-static, since the intersecting shapes themselves will also be dynamic. My first thought was to use raycasting detection, though I've only seen that in use with circles, or even ellipses. I'm curious if there's a method of using raycasting with a more rectangular approach, or if there's a totally different method already in use to accomplish this task. I would like something more exact than checking in large chunks, and since I'm using SDL2 with a logical renderer size of 1920x1080, checking if each pixel is intersecting is out of the question, as it would slow things down past a playable speed. I already have a multi-shape collision function-template in place, and I could use that, though it only checks if sides or corners are intersecting; it does not compute the overlapping area, or even find the circle's secant line, though I can't imagine it would be overly complex to implement. TL;DR: I need to find and isolate areas of a rectangle that may intersect with a circle or another rectangle without checking every single pixel on-screen.

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• Geometry shader for multiple primitives

  - by Byte56

  How can I create a geometry shader that can handle multiple primitives? For example when creating a geometry shader for triangles, I define a layout like so: layout(triangles) in; layout(triangle_strip, max_vertices=3) out; But if I use this shader then lines or points won't show up. So adding: layout(triangles) in; layout(triangle_strip, max_vertices=3) out; layout(lines) in; layout(line_strip, max_vertices=2) out; The shader will compile and run, but will only render lines (or whatever the last primitive defined is). So how do I define a single geometry shader that will handle multiple types of primitives? Or is that not possible and I need to create multiple shader programs and change shader programs before drawing each type?

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• MD5 vertex skinning problem extending to multi-jointed skeleton (GPU Skinning)

  - by Soapy

  Currently I'm trying to implement GPU skinning in my project. So far I have achieved single joint translation and rotation, and multi-jointed translation. The problem arises when I try to rotate a multi-jointed skeleton. The image above shows the current progress. The left image shows how the model should deform. The middle image shows how it deforms in my project. The right shows a better deform (still not right) inverting a certain value, which I will explain below. The way I get my animation data is by exporting it to the MD5 format (MD5mesh for mesh data and MD5anim for animation data). When I come to parse the animation data, for each frame, I check if the bone has a parent, if not, the data is passed in as is from the MD5anim file. If it does have a parent, I transform the bones position by the parents orientation, and the add this with the parents translation. Then the parent and child orientations get concatenated. This is covered at this website. if (Parent < 0){ ... // Save this data without editing it } else { Math3::vec3 rpos; Math3::quat pq = Parent.Quaternion; Math3::quat pqi(pq); pqi.InvertUnitQuat(); pqi.Normalise(); Math3::quat::RotateVector3(rpos, pq, jv); Math3::vec3 npos(rpos + Parent.Pos); this->Translation = npos; Math3::quat nq = pq * jq; nq.Normalise(); this->Quaternion = nq; } And to achieve the image to the right, all I need to do is to change Math3::quat::RotateVector3(rpos, pq, jv); to Math3::quat::RotateVector3(rpos, pqi, jv);, why is that? And this is my skinning shader. SkinningShader.vert #version 330 core smooth out vec2 vVaryingTexCoords; smooth out vec3 vVaryingNormals; smooth out vec4 vWeightColor; uniform mat4 MV; uniform mat4 MVP; uniform mat4 Pallete[55]; uniform mat4 invBindPose[55]; layout(location = 0) in vec3 vPos; layout(location = 1) in vec2 vTexCoords; layout(location = 2) in vec3 vNormals; layout(location = 3) in int vSkeleton[4]; layout(location = 4) in vec3 vWeight; void main() { vec4 wpos = vec4(vPos, 1.0); vec4 norm = vec4(vNormals, 0.0); vec4 weight = vec4(vWeight, (1.0f-(vWeight[0] + vWeight[1] + vWeight[2]))); normalize(weight); mat4 BoneTransform; for(int i = 0; i < 4; i++) { if(vSkeleton[i] != -1) { if(i == 0) { // These are interchangable for some reason // BoneTransform = ((invBindPose[vSkeleton[i]] * Pallete[vSkeleton[i]]) * weight[i]); BoneTransform = ((Pallete[vSkeleton[i]] * invBindPose[vSkeleton[i]]) * weight[i]); } else { // These are interchangable for some reason // BoneTransform += ((invBindPose[vSkeleton[i]] * Pallete[vSkeleton[i]]) * weight[i]); BoneTransform += ((Pallete[vSkeleton[i]] * invBindPose[vSkeleton[i]]) * weight[i]); } } } wpos = BoneTransform * wpos; vWeightColor = weight; vVaryingTexCoords = vTexCoords; vVaryingNormals = normalize(vec3(vec4(vNormals, 0.0) * MV)); gl_Position = wpos * MVP; } The Pallete matrices are the matrices calculated using the above code (a rotation and translation matrix get created from the translation and quaternion). The invBindPose matrices are simply the inverted matrices created from the joints in the MD5mesh file. Update 1 I looked at GLM to compare the values I get with my own implementation. They turn out to be exactly the same. So now i'm checking if there's a problem with matrix creation... Update 2 Looked at GLM again to compare matrix creation using quaternions. Turns out that's not the problem either.

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• Away3D & Directional Light w/ Rotating Meshes

  - by seethru

  This is likely a stupid error but I can't seem to find what I've done wrong. I've got a simple scene with 10 cylinders rotating at a default speed. If I grab one of these cylinders I can rotate it in the opposite direction or at a greater speed. I have a single directional light in the scene. It would appear that the directional light is only calculated at initialization and not on further frames. The shadow created by the light rotates with the cylinder giving the impression that the light is rotating when it isn't. Camera & Light Initialization _view = new View3D(); addChild(_view); _view.antiAlias = 4; _view.backgroundColor = 0xFFFFFF; _view.camera.z = -850; _view.camera.y = 0; _view.camera.x = 0; _view.camera.lookAt(new Vector3D()); _view.camera.lens = new PerspectiveLens(15); _view.mousePicker = PickingType.RAYCAST_BEST_HIT; _light = new DirectionalLight(); _light.z = -850; _light.direction = new Vector3D(1, 1, 1); _light.color = 0xFFFFFF; _light.ambient = 0.1; _light.diffuse = 0.7; _view.scene.addChild(_light); Mesh and Material creation var material:TextureMaterial = new TextureMaterial(createPow2Texture(sprite, _colors[i]) , true, false, true); material.animateUVs = true; material.lightPicker = _lightPicker; cylinder = new Mesh(new CylinderGeometry(radius, radius, 13, 70, 1, true, true), material); cylinder.subMeshes[0].scaleU = spriteWidth / sprite.width; cylinder.y = y; cylinder.mouseEnabled = true; cylinder.pickingCollider = PickingColliderType.AS3_BEST_HIT; cylinder.addEventListener(MouseEvent3D.MOUSE_OVER, onMouseOverMesh); cylinder.addEventListener(MouseEvent3D.MOUSE_MOVE, onMouseOverMesh); cylinder.addEventListener(MouseEvent3D.MOUSE_OUT, onMouseOutMesh); _cylinders.push(cylinder); Frame private function onEnterFrame(event:Event):void { for each (var mesh:Mesh in _cylinders) { if (mesh == _mouseOverMesh) continue; mesh.rotationY += 0.25; } _view.render(); }

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• Skyrim Nexus Mods on Xbox 360 by use of dawnguard?

  - by user17895

  i think it's possible i opened up the dawnguard marketplace content and it consists 3 files: dawnguard.bsa < mod dawnguard.esp <- mod installing file. and spa.bin <-dont know where this is for. and it has been confirmed you can use the top 2 files on pc for a not fully functional dawnguard (barely functional to be exact) and if we could just replace or add a few other bsa and esp files to this marketplace content we could get mods up and running on xbox altough i need confirmation on this. I also have no clue where the spa.bin file for is, i need to examine it some further. Further this is adding a few non-distributed Files to marketplace content and wont get you booted from XBL. Also if anyone wants to examine these files for further information i will gladly share them with you. if you have any information or answers please email me at [email protected] thx

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• Normal maps red in OpenGL?

  - by KaiserJohaan

  I am using Assimp to import 3d models, and FreeImage to parse textures. The problem I am having is that the normal maps are actually red rather than blue when I try to render them as normal diffuse textures. http://i42.tinypic.com/289ing3.png When I open the images in a image-viewing program they do indeed show up as blue. Heres when I create the texture; OpenGLTexture::OpenGLTexture(const std::vector<uint8_t>& textureData, uint32_t textureWidth, uint32_t textureHeight, TextureType textureType, Logger& logger) : mLogger(logger), mTextureID(gNextTextureID++), mTextureType(textureType) { glGenTextures(1, &mTexture); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, mTexture); CHECK_GL_ERROR(mLogger); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureWidth, textureHeight, 0, glTextureFormat, GL_UNSIGNED_BYTE, &textureData[0]); CHECK_GL_ERROR(mLogger); glGenerateMipmap(GL_TEXTURE_2D); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, 0); CHECK_GL_ERROR(mLogger); } Here is my fragment shader. You can see I just commented out the normal-map parsing and treated the normal map texture as the diffuse texture to display it and illustrate the problem. As for the rest of the code it interacts as expected with the diffuse textures so I dont see a obvious problem there. "#version 330 \n \ \n \ layout(std140) uniform; \n \ \n \ const int MAX_LIGHTS = 8; \n \ \n \ struct Light \n \ { \n \ vec4 mLightColor; \n \ vec4 mLightPosition; \n \ vec4 mLightDirection; \n \ \n \ int mLightType; \n \ float mLightIntensity; \n \ float mLightRadius; \n \ float mMaxDistance; \n \ }; \n \ \n \ uniform UnifLighting \n \ { \n \ vec4 mGamma; \n \ vec3 mViewDirection; \n \ int mNumLights; \n \ \n \ Light mLights[MAX_LIGHTS]; \n \ } Lighting; \n \ \n \ uniform UnifMaterial \n \ { \n \ vec4 mDiffuseColor; \n \ vec4 mAmbientColor; \n \ vec4 mSpecularColor; \n \ vec4 mEmissiveColor; \n \ \n \ bool mHasDiffuseTexture; \n \ bool mHasNormalTexture; \n \ bool mLightingEnabled; \n \ float mSpecularShininess; \n \ } Material; \n \ \n \ uniform sampler2D unifDiffuseTexture; \n \ uniform sampler2D unifNormalTexture; \n \ \n \ in vec3 frag_position; \n \ in vec3 frag_normal; \n \ in vec2 frag_texcoord; \n \ in vec3 frag_tangent; \n \ in vec3 frag_bitangent; \n \ \n \ out vec4 finalColor; " " \n \ \n \ void CalcGaussianSpecular(in vec3 dirToLight, in vec3 normal, out float gaussianTerm) \n \ { \n \ vec3 viewDirection = normalize(Lighting.mViewDirection); \n \ vec3 halfAngle = normalize(dirToLight + viewDirection); \n \ \n \ float angleNormalHalf = acos(dot(halfAngle, normalize(normal))); \n \ float exponent = angleNormalHalf / Material.mSpecularShininess; \n \ exponent = -(exponent * exponent); \n \ \n \ gaussianTerm = exp(exponent); \n \ } \n \ \n \ vec4 CalculateLighting(in Light light, in vec4 diffuseTexture, in vec3 normal) \n \ { \n \ if (light.mLightType == 1) // point light \n \ { \n \ vec3 positionDiff = light.mLightPosition.xyz - frag_position; \n \ float dist = max(length(positionDiff) - light.mLightRadius, 0); \n \ \n \ float attenuation = 1 / ((dist/light.mLightRadius + 1) * (dist/light.mLightRadius + 1)); \n \ attenuation = max((attenuation - light.mMaxDistance) / (1 - light.mMaxDistance), 0); \n \ \n \ vec3 dirToLight = normalize(positionDiff); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (attenuation * angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (attenuation * gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 2) // directional light \n \ { \n \ vec3 dirToLight = normalize(light.mLightDirection.xyz); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 4) // ambient light \n \ return diffuseTexture * Material.mAmbientColor * light.mLightIntensity * light.mLightColor; \n \ else \n \ return vec4(0.0); \n \ } \n \ \n \ void main() \n \ { \n \ vec4 diffuseTexture = vec4(1.0); \n \ if (Material.mHasDiffuseTexture) \n \ diffuseTexture = texture(unifDiffuseTexture, frag_texcoord); \n \ \n \ vec3 normal = frag_normal; \n \ if (Material.mHasNormalTexture) \n \ { \n \ diffuseTexture = vec4(normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0), 1.0); \n \ // vec3 normalTangentSpace = normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0); \n \ //mat3 tangentToWorldSpace = mat3(normalize(frag_tangent), normalize(frag_bitangent), normalize(frag_normal)); \n \ \n \ // normal = tangentToWorldSpace * normalTangentSpace; \n \ } \n \ \n \ if (Material.mLightingEnabled) \n \ { \n \ vec4 accumLighting = vec4(0.0); \n \ \n \ for (int lightIndex = 0; lightIndex < Lighting.mNumLights; lightIndex++) \n \ accumLighting += Material.mEmissiveColor * diffuseTexture + \n \ CalculateLighting(Lighting.mLights[lightIndex], diffuseTexture, normal); \n \ \n \ finalColor = pow(accumLighting, Lighting.mGamma); \n \ } \n \ else { \n \ finalColor = pow(diffuseTexture, Lighting.mGamma); \n \ } \n \ } \n"; Why is this? does normal-map textures need some sort of special treatment in opengl?

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• Converting from different handedness coordinate systems

  - by SirYakalot

  I am currently porting a demo from XNA to DirectX which, as I understand it, both have coordinate systems with different handednesses. What are the things I need to bare in mind when converting between the two? I understand not everything needs to be changed. Also I notice that many of the 3D maths functions in some of the direct3D libraries have right handed and left handed alternatives. Would it be better to just use these?

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• Render 2 images that uses different shaders

  - by Code Vader

  Based on the giawa/nehe tutorials, how can I render 2 images with different shaders. I'm pretty new to OpenGl and shaders so I'm not completely sure whats happening in my code, but I think the shaders that is called last overwrites the first one. private static void OnRenderFrame() { // calculate how much time has elapsed since the last frame watch.Stop(); float deltaTime = (float)watch.ElapsedTicks / System.Diagnostics.Stopwatch.Frequency; watch.Restart(); // use the deltaTime to adjust the angle of the cube angle += deltaTime; // set up the OpenGL viewport and clear both the color and depth bits Gl.Viewport(0, 0, width, height); Gl.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit); // use our shader program and bind the crate texture Gl.UseProgram(program); //<<<<<<<<<<<< TOP PYRAMID // set the transformation of the top_pyramid program["model_matrix"].SetValue(Matrix4.CreateRotationY(angle * rotate_cube)); program["enable_lighting"].SetValue(lighting); // bind the vertex positions, UV coordinates and element array Gl.BindBufferToShaderAttribute(top_pyramid, program, "vertexPosition"); Gl.BindBufferToShaderAttribute(top_pyramidNormals, program, "vertexNormal"); Gl.BindBufferToShaderAttribute(top_pyramidUV, program, "vertexUV"); Gl.BindBuffer(top_pyramidTrianlges); // draw the textured top_pyramid Gl.DrawElements(BeginMode.Triangles, top_pyramidTrianlges.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); //<<<<<<<<<< CUBE // set the transformation of the cube program["model_matrix"].SetValue(Matrix4.CreateRotationY(angle * rotate_cube)); program["enable_lighting"].SetValue(lighting); // bind the vertex positions, UV coordinates and element array Gl.BindBufferToShaderAttribute(cube, program, "vertexPosition"); Gl.BindBufferToShaderAttribute(cubeNormals, program, "vertexNormal"); Gl.BindBufferToShaderAttribute(cubeUV, program, "vertexUV"); Gl.BindBuffer(cubeQuads); // draw the textured cube Gl.DrawElements(BeginMode.Quads, cubeQuads.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); //<<<<<<<<<<<< BOTTOM PYRAMID // set the transformation of the bottom_pyramid program["model_matrix"].SetValue(Matrix4.CreateRotationY(angle * rotate_cube)); program["enable_lighting"].SetValue(lighting); // bind the vertex positions, UV coordinates and element array Gl.BindBufferToShaderAttribute(bottom_pyramid, program, "vertexPosition"); Gl.BindBufferToShaderAttribute(bottom_pyramidNormals, program, "vertexNormal"); Gl.BindBufferToShaderAttribute(bottom_pyramidUV, program, "vertexUV"); Gl.BindBuffer(bottom_pyramidTrianlges); // draw the textured bottom_pyramid Gl.DrawElements(BeginMode.Triangles, bottom_pyramidTrianlges.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); //<<<<<<<<<<<<< STAR Gl.Disable(EnableCap.DepthTest); Gl.Enable(EnableCap.Blend); Gl.BlendFunc(BlendingFactorSrc.SrcAlpha, BlendingFactorDest.One); Gl.BindTexture(starTexture); //calculate the camera position using some fancy polar co-ordinates Vector3 position = 20 * new Vector3(Math.Cos(phi) * Math.Sin(theta), Math.Cos(theta), Math.Sin(phi) * Math.Sin(theta)); Vector3 upVector = ((theta % (Math.PI * 2)) > Math.PI) ? Vector3.Up : Vector3.Down; program_2["view_matrix"].SetValue(Matrix4.LookAt(position, Vector3.Zero, upVector)); // make sure the shader program and texture are being used Gl.UseProgram(program_2); // loop through the stars, drawing each one for (int i = 0; i < stars.Count; i++) { // set the position and color of this star program_2["model_matrix"].SetValue(Matrix4.CreateTranslation(new Vector3(stars[i].dist, 0, 0)) * Matrix4.CreateRotationZ(stars[i].angle)); program_2["color"].SetValue(stars[i].color); Gl.BindBufferToShaderAttribute(star, program_2, "vertexPosition"); Gl.BindBufferToShaderAttribute(starUV, program_2, "vertexUV"); Gl.BindBuffer(starQuads); Gl.DrawElements(BeginMode.Quads, starQuads.Count, DrawElementsType.UnsignedInt, IntPtr.Zero); // update the position of the star stars[i].angle += (float)i / stars.Count * deltaTime * 2 * rotate_stars; stars[i].dist -= 0.2f * deltaTime * rotate_stars; // if we've reached the center then move this star outwards and give it a new color if (stars[i].dist < 0f) { stars[i].dist += 5f; stars[i].color = new Vector3(generator.NextDouble(), generator.NextDouble(), generator.NextDouble()); } } Glut.glutSwapBuffers(); } The same goes for the textures, whichever one I mention last gets applied to both object?

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• 2D OBB collision detection, resolving collisions?

  - by Milo

  I currently use OBBs and I have a vehicle that is a rigid body and some buildings. Here is my update() private void update() { camera.setPosition((vehicle.getPosition().x * camera.getScale()) - ((getWidth() ) / 2.0f), (vehicle.getPosition().y * camera.getScale()) - ((getHeight() ) / 2.0f)); //camera.move(input.getAnalogStick().getStickValueX() * 15.0f, input.getAnalogStick().getStickValueY() * 15.0f); if(input.isPressed(ControlButton.BUTTON_GAS)) { vehicle.setThrottle(1.0f, false); } if(input.isPressed(ControlButton.BUTTON_BRAKE)) { vehicle.setBrakes(1.0f); } vehicle.setSteering(input.getAnalogStick().getStickValueX()); vehicle.update(16.6666f / 1000.0f); ArrayList<Building> buildings = city.getBuildings(); for(Building b : buildings) { if(vehicle.getRect().overlaps(b.getRect())) { vehicle.update(-17.0f / 1000.0f); break; } } } The collision detection works well. What doesn't is how they are dealt with. My goal is simple. If the vehicle hits a building, it should stop, and never go into the building. When I apply negative torque to reverse the car should not feel buggy and move away from the building. I don't want this to look buggy. This is my rigid body class: class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position, getWidth(), getHeight(), angle); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { //integrate physics //linear Vector2D acceleration = Vector2D.scalarDivide(forces, mass); velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); c = Vector2D.add(getRect().getCenter(), Vector2D.scalarMultiply(velocity , timeStep)); setCenter(c.x, c.y); forces = new Vector2D(0,0); //clear forces //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { Matrix mat = new Matrix(); float[] Vector2Ds = new float[2]; Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { Matrix mat = new Matrix(); float[] Vectors = new float[2]; Vectors[0] = world.x; Vectors[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vectors); return new Vector2D(Vectors[0], Vectors[1]); } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { Vector2D tangent = new Vector2D(-worldOffset.y, worldOffset.x); return Vector2D.add( Vector2D.scalarMultiply(tangent, angularVelocity) , velocity); } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces = Vector2D.add(forces ,worldForce); //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } } Essentially, when any rigid body hits a building it should exhibit the same behavior. How is collision solving usually done? Thanks

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• Index out of bounds, Java bukkit plugin

  - by Robby Duke

  I'm getting index out of bounds errors in my Bukkit plugin, and it's really beginning to piss me off... I for the life of me can't figure this issue out! Caused by: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1 This is where I believe the code to be erroring... for(int i = 0; i <= staffOnline.size(); i++) { if(i == staffOnline.size()) { staffList = staffList + staffOnline.get(i); } else { staffList = staffList + staffOnline.get(i) + ", "; } }

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• RenderTarget2D behavior in XNA

  - by Utkarsh Sinha

  I've been dabbling with XNA for a couple of days now. This chunk of code doesn't work as I expect. The goal is to render sprites individually and composite them on another rendertarget. P = RenderTarget2D(with RenderTargetUsage.PreserveContents) D = RenderTarget2D(with RenderTargetUsage.DiscardContents) for all sprites: graphicsDevice.SetRenderTarget(D); <draw sprite i> graphicsDevice.SetRenderTarget(P); <Draw D> graphicsDevice.SetRenderTarget(null); <Draw P> The result I get is - only the last sprite is visible. I'm sure I'm missing some piece of information about RenderTarget2D. Any hints on what that might be? Cross posted from - http://stackoverflow.com/questions/9970349/weird-rendertarget2d-behaviour

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