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  • How can I render a semi transparent model with OpenGL correctly?

    - by phobitor
    I'm using OpenGL ES 2 and I want to render a simple model with some level of transparency. I'm just starting out with shaders, and I wrote a simple diffuse shader for the model without any issues but I don't know how to add transparency to it. I tried to set my fragment shader's output (gl_FragColor) to a non opaque alpha value but the results weren't too great. It sort of works, but it looks like certain model triangles are only rendered based on the camera position... It's really hard to describe what's wrong so please watch this short video I recorded: http://www.youtube.com/watch?v=s0JqA0rZabE I thought this was a depth testing issue so I tried playing around with enabling/disabling depth testing and back face culling. Enabling back face culling changes the output slightly but the problem in the video is still there. Enabling/disabling depth testing doesn't seem to do anything. Could anyone explain what I'm seeing and how I can add some simple transparency to my model with the shader? I'm not looking for advanced order independent transparency implementations. edit: Vertex Shader: // color varying for fragment shader varying mediump vec3 LightIntensity; varying highp vec3 VertexInModelSpace; void main() { // vec4 LightPosition = vec4(0.0, 0.0, 0.0, 1.0); vec3 LightColor = vec3(1.0, 1.0, 1.0); vec3 DiffuseColor = vec3(1.0, 0.25, 0.0); // find the vector from the given vertex to the light source vec4 vertexInWorldSpace = gl_ModelViewMatrix * vec4(gl_Vertex); vec3 normalInWorldSpace = normalize(gl_NormalMatrix * gl_Normal); vec3 lightDirn = normalize(vec3(LightPosition-vertexInWorldSpace)); // save vertexInWorldSpace VertexInModelSpace = vec3(gl_Vertex); // calculate light intensity LightIntensity = LightColor * DiffuseColor * max(dot(lightDirn,normalInWorldSpace),0.0); // calculate projected vertex position gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } Fragment Shader: // varying to define color varying vec3 LightIntensity; varying vec3 VertexInModelSpace; void main() { gl_FragColor = vec4(LightIntensity,0.5); }

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  • Calculating the force of an impact?

    - by meds
    I'm trying to figure out a way to determine the force two objects collide in. I have two vectors defining their linear velocity at the time of impact, their mass and their angular velocity. Keep in mind this is all for a 2D physics engine. I don't think it's as simple as adding up these values and figuring out if it's large enogh it makes a large impact since that doesn't take into account if the two objects are travelling in the same direction (as an example). Any ideas?

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  • Parsing glGetShaderInfoLog() to get error info. Is this reliable, or is there a better way?

    - by m4ttbush
    I want to get a list of errors and their line numbers so I can display the error information different to how it's formatted in the error string, and also show the line in error. It looks easy enough to just parse the result of glGetShaderInfoLog(), look for "ERROR:" then read the next number up to : and then the next, and then the error description up to the next newline. But the OpenGL docs say "Application developers should not expect different OpenGL implementations to produce identical information logs." Which makes me worry that my code may behave incorrectly on different systems. I don't need them to be identical, I just need them to follow the same format. So is there a better way to get a list of errors with line number separate, is it safe to assume that they'll always follow the "ERROR: 0:123:" format, or is there simply no reliable way to do this? Thanks!

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  • Translating an object along its heading

    - by Kuros
    I am working on a simulation that requires me to have several objects moving around in 3D space (text output of their current position on the grid and heading is fine, I do not need graphics), and I am having some trouble getting objects to move along their relative headings. I have a basic understanding of vectors and matrices. I am using a vector to represent their position, and I am also using Euler Angles. I can translate one of my entities with a matrix along whatever axis, and I can alter their heading. For example, if I have an entity at (order is XYZ) 1, 1, 1, with a heading of 0, I can apply a translation matrix to get them to talk to 1, 1, 2 fine. However, if I change their heading to 270, they still walk to 1, 1, 3, instead of 2, 1, 2 as I desire. I have a feeling that my problem lies in not translating my matrix from world space to object space, but I am not sure how to go about that. How can I do this? Addition: I am using 3D vectors to represent their current position and their heading (using the three euler angles). For now, all I want to do is have an entity walk in a square, reporting their current position at each step. So, assuming it starts at 10, 10, 10 I want it to walk as follows: 10,10,10 -> 10, 10, 15 10, 10, 15 -> 5, 10, 15 5, 10, 15 -> 5, 10, 10 5, 10, 10 -> 10, 10, 10 My 1 Z unit translation matrix is as follows: [1 0 0 0] [0 1 0 0] [0 0 1 1] [0 0 0 1] My rotation matrix is as follows: [0 0 1 0] [0 1 0 0] [-1 0 0 0] [0 0 0 1]

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  • XNA: Retrieve texture file name during runtime

    - by townsean
    I'm trying to retrieve the names of the texture files (or their locations) on a mesh. I realize that the texture file name information is not preserved when the model is loaded. I've been doing tons of searching and some experimenting but I've been met with no luck. I've gathered that I need to extended the content pipeline and store the file location in somewhere like ModelMeshPart.Tag. My problem is, even when I'm trying to make my own custom processor, I still can't figure out where the texture file name is. :( Any thoughts? Thanks! UPDATE: Okay, so I found something kind of promising. NodeContent.Identity.SourceFilename, only that returns the location of my .X model. When I go down the node tree he is always null. Then there's the ContentItem.Name property. It seems to have names of my mesh, but not my actual texture file names. :(

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  • Possible to pass pygame data to memory map block?

    - by toozie21
    I am building a matrix out of addressable pixels and it will be run by a Pi (over the ethernet bus). The matrix will be 75 pixels wide and 20 pixels tall. As a side project, I thought it would be neat to run pong on it. I've seen some python based pong tutorials for Pi, but the problem is that they want to pass the data out to a screen via pygame.display function. I have access to pass pixel information using a memory map block, so is there anyway to do that with pygame instead of passing it out the video port? In case anyone is curious, this was the pong tutorial I was looking at: Pong Tutorial

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  • ERROR #342: DEVICE_SHADER_LINKAGE_SEMANTICNAME_NOT_FOUND

    - by Telanor
    I've stared at this for at least half an hour now and I cannot figure out what directx is complaining about. I know this error normally means you put float3 instead of a float4 or something like that, but I've checked over and over and as far as I can tell, everything matches. This is the full error message: D3D11: ERROR: ID3D11DeviceContext::DrawIndexed: Input Assembler - Vertex Shader linkage error: Signatures between stages are incompatible. The input stage requires Semantic/Index (COLOR,0) as input, but it is not provided by the output stage. [ EXECUTION ERROR #342: DEVICE_SHADER_LINKAGE_SEMANTICNAME_NOT_FOUND ] This is the vertex shader's input signature as seen in PIX: // Input signature: // // Name Index Mask Register SysValue Format Used // -------------------- ----- ------ -------- -------- ------ ------ // POSITION 0 xyz 0 NONE float xyz // NORMAL 0 xyz 1 NONE float // COLOR 0 xyzw 2 NONE float The HLSL structure looks like this: struct VertexShaderInput { float3 Position : POSITION0; float3 Normal : NORMAL0; float4 Color: COLOR0; }; The input layout, from PIX, is: The C# structure holding the data looks like this: [StructLayout(LayoutKind.Sequential)] public struct PositionColored { public static int SizeInBytes = Marshal.SizeOf(typeof(PositionColored)); public static InputElement[] InputElements = new[] { new InputElement("POSITION", 0, Format.R32G32B32_Float, 0), new InputElement("NORMAL", 0, Format.R32G32B32_Float, 0), new InputElement("COLOR", 0, Format.R32G32B32A32_Float, 0) }; Vector3 position; Vector3 normal; Vector4 color; #region Properties ... #endregion public PositionColored(Vector3 position, Vector3 normal, Vector4 color) { this.position = position; this.normal = normal; this.color = color; } public override string ToString() { StringBuilder sb = new StringBuilder(base.ToString()); sb.Append(" Position="); sb.Append(position); sb.Append(" Color="); sb.Append(Color); return sb.ToString(); } } SizeInBytes comes out to 40, which is correct (4*3 + 4*3 + 4*4 = 40). Can anyone find where the mistake is?

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  • What are the semantics of glRotate and glTranslate's parameters?

    - by Zarkopafilis
    I have been trying to play with OpenGL after watching some tutorials and I don't understand how the glTranslatef and glRotatef functions work. I believe a simple picture would help me. I understand that glTranslatef changes the position of the "camera" (but does it change the position in wich the shapes are getting drawn)? However, I don't understand the rotation concept at all. If I do glRotatef(1,0,0,1) it makes my quad spin around. If I just do glRotatef(1,0,0,0) it makes the quad smaller (further away) but if I try to rotate around the X or Y axis, I get a black screen. I don't understand the angle either. Help would be appreciated.

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  • How to rotate a group of objects around a common center?

    - by user1662292
    I've made a model in 3D Studio Max 9. It consists of a variety of cubes, clyinders etc. In XNA I've imported the model okay and it shows correctly. However, when I apply rotation, each component in the model rotates around it's own centre. I want the model to rotate as a single unit. I've linked the components in 3D Max and they rotate as I want in Max. protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); model = Content.Load<Model>("Models/Alien1"); } protected override void Update(GameTime gameTime) { camera.Update(1f, new Vector3(), graphics.GraphicsDevice.Viewport.AspectRatio); rotation += 0.1f; base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); Matrix[] transforms = new Matrix[model.Bones.Count]; model.CopyAbsoluteBoneTransformsTo(transforms); Matrix worldMatrix = Matrix.Identity; Matrix rotationYMatrix = Matrix.CreateRotationY(rotation); Matrix translateMatrix = Matrix.CreateTranslation(location); worldMatrix = rotationYMatrix * translateMatrix; foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = worldMatrix * transforms[mesh.ParentBone.Index]; effect.View = camera.viewMatrix; effect.Projection = camera.projectionMatrix; effect.EnableDefaultLighting(); effect.PreferPerPixelLighting = true; } mesh.Draw(); } base.Draw(gameTime); } More Info: Rotating the object via it's properties works fine so I'm guessing there's something up with the code rather than with the object itself. Translating the object also causes the objects to get moved independently of each other rather than as a single model and each piece becomes spread around the scene. The model is in .X format.

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  • Understanding implementation of glu.PickMatrix()

    - by stoney78us
    I am working on an OpenGL project which requires object selection feature. I use OpenTK framework to do this; however OpenTK doesn't support glu.PickMatrix() method to define the picking region. I ended up googling its implementation and here is what i got: void GluPickMatrix(double x, double y, double deltax, double deltay, int[] viewport) { if (deltax <= 0 || deltay <= 0) { return; } GL.Translate((viewport[2] - 2 * (x - viewport[0])) / deltax, (viewport[3] - 2 * (y - viewport[1])) / deltay, 0); GL.Scale(viewport[2] / deltax, viewport[3] / deltay, 1.0); } I totally fail to understand this piece of code. Moreover, this doesn't work with my following code sample: //selectbuffer private int[] _selectBuffer = new int[512]; private void Init() { float[] triangleVertices = new float[] { 0.0f, 1.0f, 0.0f, -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f }; float[] _triangleColors = new float[] { 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f }; GL.GenBuffers(2, _vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, _vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(sizeof(float) * _triangleVertices.Length), _triangleVertices, BufferUsageHint.StaticDraw); GL.VertexPointer(3, VertexPointerType.Float, 0, 0); GL.BindBuffer(BufferTarget.ArrayBuffer, _vBO[1]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(sizeof(float) * _triangleColors.Length), _triangleColors, BufferUsageHint.StaticDraw); GL.ColorPointer(3, ColorPointerType.Float, 0, 0); GL.EnableClientState(ArrayCap.VertexArray); GL.EnableClientState(ArrayCap.ColorArray); //Selectbuffer set up GL.SelectBuffer(512, _selectBuffer); } private void glControlWindow_Paint(object sender, PaintEventArgs e) { GL.Clear(ClearBufferMask.ColorBufferBit); GL.Clear(ClearBufferMask.DepthBufferBit); float[] eyes = { 0.0f, 0.0f, -10.0f }; float[] target = { 0.0f, 0.0f, 0.0f }; Matrix4 projection = Matrix4.CreatePerspectiveFieldOfView(0.785398163f, 4.0f / 3.0f, 0.1f, 100f); //45 degree = 0.785398163 rads Matrix4 view = Matrix4.LookAt(eyes[0], eyes[1], eyes[2], target[0], target[1], target[2], 0, 1, 0); Matrix4 model = Matrix4.Identity; Matrix4 MV = view * model; //First Clear Buffers GL.Clear(ClearBufferMask.ColorBufferBit); GL.Clear(ClearBufferMask.DepthBufferBit); GL.MatrixMode(MatrixMode.Projection); GL.LoadIdentity(); GL.LoadMatrix(ref projection); GL.MatrixMode(MatrixMode.Modelview); GL.LoadIdentity(); GL.LoadMatrix(ref MV); GL.Viewport(0, 0, glControlWindow.Width, glControlWindow.Height); GL.Enable(EnableCap.DepthTest); //Enable correct Z Drawings GL.DepthFunc(DepthFunction.Less); //Enable correct Z Drawings GL.MatrixMode(MatrixMode.Modelview); GL.PushMatrix(); GL.Translate(3.0f, 0.0f, 0.0f); DrawTriangle(); GL.PopMatrix(); GL.PushMatrix(); GL.Translate(-3.0f, 0.0f, 0.0f); DrawTriangle(); GL.PopMatrix(); //Finally... GraphicsContext.CurrentContext.VSync = true; //Caps frame rate as to not over run GPU glControlWindow.SwapBuffers(); //Takes from the 'GL' and puts into control } private void DrawTriangle() { GL.BindBuffer(BufferTarget.ArrayBuffer, _vBO[0]); GL.VertexPointer(3, VertexPointerType.Float, 0, 0); GL.EnableClientState(ArrayCap.VertexArray); GL.DrawArrays(BeginMode.Triangles, 0, 3); GL.DisableClientState(ArrayCap.VertexArray); } //mouse click event implementation private void glControlWindow_MouseClick(object sender, System.Windows.Forms.MouseEventArgs e) { //Enter Select mode. Pretend drawing. GL.RenderMode(RenderingMode.Select); int[] viewport = new int[4]; GL.GetInteger(GetPName.Viewport, viewport); GL.PushMatrix(); GL.MatrixMode(MatrixMode.Projection); GL.LoadIdentity(); GluPickMatrix(e.X, e.Y, 5, 5, viewport); Matrix4 projection = Matrix4.CreatePerspectiveFieldOfView(0.785398163f, 4.0f / 3.0f, 0.1f, 100f); // this projection matrix is the same as one in glControlWindow_Paint method. GL.LoadMatrix(ref projection); GL.MatrixMode(MatrixMode.Modelview); int i = 0; int hits; GL.PushMatrix(); GL.Translate(3.0f, 0.0f, 0.0f); GL.PushName(i); DrawTriangle(); GL.PopName(); GL.PopMatrix(); i++; GL.PushMatrix(); GL.Translate(-3.0f, 0.0f, 0.0f); GL.PushName(i); DrawTriangle(); GL.PopName(); GL.PopMatrix(); hits = GL.RenderMode(RenderingMode.Render); .....hits processing code goes here... GL.PopMatrix(); glControlWindow.Invalidate(); } I expect to get only one hit everytime i click inside a triangle, but i always get 2 no matter where i click. I suspect there is something wrong with the implementation of the GluPickMatrix, I haven't figured out yet.

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  • XNA - 3D AABB collision detection and response

    - by fastinvsqrt
    I've been fiddling around with 3D AABB collision in my voxel engine for the last couple of days, and every method I've come up with thus far has been almost correct, but each one never quite worked exactly the way I hoped it would. Currently what I do is get two bounding boxes for my entity, one modified by the X translation component and the other by the Z component, and check if each collides with any of the surrounding chunks (chunks have their own octrees that are populated only with blocks that support collision). If there is a collision, then I cast out rays into that chunk to get the shortest collision distance, and set the translation component to that distance if the component is greater than the distance. The problem is that sometimes collisions aren't even registered. Here's a video on YouTube that I created showing what I mean. I suspect the problem may be with the rays that I cast to get the collision distance not being where I think they are, but I'm not entirely sure what would be wrong with them if they are indeed the problem. Here is my code for collision detection and response in the X direction (the Z direction is basically the same): // create the XZ offset vector Vector3 offsXZ = new Vector3( ( _translation.X > 0.0f ) ? SizeX / 2.0f : ( _translation.X < 0.0f ) ? -SizeX / 2.0f : 0.0f, 0.0f, ( _translation.Z > 0.0f ) ? SizeZ / 2.0f : ( _translation.Z < 0.0f ) ? -SizeZ / 2.0f : 0.0f ); // X physics BoundingBox boxx = GetBounds( _translation.X, 0.0f, 0.0f ); if ( _translation.X > 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Right, offsXZ ) - 0.0001f; if ( dist < _translation.X ) { _translation.X = dist; } } } } else if ( _translation.X < 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Left, offsXZ ) - 0.0001f; if ( dist < -_translation.X ) { _translation.X = -dist; } } } } And here is my implementation for GetShortestCollisionDistance: private float GetShortestCollisionDistance( Chunk chunk, Vector3 rayDir, Vector3 offs ) { int startY = (int)( -SizeY / 2.0f ); int endY = (int)( SizeY / 2.0f ); int incY = (int)Cube.Size; float dist = Chunk.Size; for ( int y = startY; y <= endY; y += incY ) { // Position is the center of the entity's bounding box Ray ray = new Ray( new Vector3( Position.X + offs.X, Position.Y + offs.Y + y, Position.Z + offs.Z ), rayDir ); // Chunk.GetIntersections(Ray) returns Dictionary<Block, float?> foreach ( var pair in chunk.GetIntersections( ray ) ) { if ( pair.Value.HasValue && pair.Value.Value < dist ) { dist = pair.Value.Value; } } } return dist; } I realize some of this code can be consolidated to help with speed, but my main concern right now is to get this bit of physics programming to actually work.

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  • Estimating costs in a GOAP system

    - by fullwall
    I'm currently developing a GOAP system in Java. An explanation of GOAP can be found at http://web.media.mit.edu/~jorkin/goap.html. Essentially, it's using A* to plot between Actions that mutate the world state. To provide a fair chance for all Actions and Goals to execute, I'm using a heuristic function to estimate the cost of doing something. What is the best way to estimate this cost so that it is comparable to all the other costs? As an example, estimating the cost of running away from an enemy versus attacking it - how should the cost be calculated to be comparable?

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  • Tetris : Effective rotation

    - by hqt
    I rotate each piece by rotation formula. More detail, because rotation angle is 90 so : xNew = y; yNew = -x; But my method has met two problems : 1) Out of box : each type of pieces is fit in square 4x4. (0,0 at under left) But by this rotation, at some case they will out of this box. For example, there is a point with coordinate (5,6) So, please help me how to fit these coordinate into 4x4 box again, or give me another formula for this. 2) at I case : (4 squares at same row or same column), just has two rotations case. but in method above, they still has 4 pieces. So, how to prevent this. Thanks :)

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  • Basic modelling of radar

    - by Hawk66
    I'm currently researching how to model/simulate radar for my naval simulation. Since the emphasis is on modelling ASW or submarines in general, I need only a basic radar model - at least for the beginning. So, does anybody know a resource for such a simple model? The model should take signal strength of the sensor, the size of the target and the terrain (height/ground clutter) into account. Thanks.

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  • Assigning a colour to imorted obj. files that are being used as default material

    - by Salino
    I am having a problem with assigning a colour to the different meshes that I have on one object. The technique that I have used is the first approach on this site. Is it possible to export a simulation (animation) from Blender to Unity? So what I would like to do is the following. I have about 107 meshes that are different frames from my shape key animation of my blender model. What I would like to have is that the first mesh will be bright green and up to the 40th mesh the colour turns to be white /greyish... the best would be if I could assign every mesh by hand a colour, however they are all default materials. And if I assign the object a colour, the whole "animation" is going to be in that colour

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  • How to calculate continuous motion with angular velocity in 2d

    - by Rulk
    I'm really new with physics. Maybe someone would be able to help me to solve the next problem: I need to calculate position of an agent on the plane(2D) in next time step where time step is large(20+ seconds) What I know about agent's motion: Initial Position Direction(normalised vector) Velocity(linear function from time ) - object always moves along it's direction Angular Velocity(linear function from time) Optional: External force direction External force (linear function from time) Running discreet simulation with t-0 is not an option.

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  • Using OpenCl to jiggle the Pipe

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

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

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

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

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

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  • How to determine collision direction between two rectangles?

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

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  • Alternatives to voxel-based terrain

    - by Neomex
    Are there any alternatives to voxel based terrains? Such terrain should be fully destructable, allow for arches, overhangs, preserve sharp features where needed and keep consistent topology. Maybe you can explain the problem that makes you ask this question? Voxel based terrain is basically just using a 3D grid of data to store data. There are lots of ways to render that data, but it doesn't get much simpler for storing it. – Byte56 Current isosurface extraction methods aren't most effective/bug-free. Cubical Marching Squares seem to solve most of the issues, however it is a relatively new method and there aren't too many resources about it. (I've found single university paper) Even if we stick to CMS, when we want to add multi-material support, we can either divide surface into multiple meshes, or pass a texture array or texture atlas to shaders, then we are limited to set amount of textures and additionally increase memory-usage alot.

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  • Rotate to a set degree then stop Unity

    - by N0xus
    I'm trying to make an object rotate up on the Y axis 90 degrees, then stop. I've got the rotating up bit working fine, it's getting it to stop once it hits 90. Some of the things I've tried include the following: float i = rotateSpeed * Time.deltaTime; while ( x != 90 ) { transform.Rotate( i, 0, 0); } int x = 0; x++; if( x == 90 ) { transform.Rotate( 0, 0, 0 ); } For some reason I can't get this simple thing to work. What am I missing / not doing?

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  • Spherical harmonics lighting interpolation

    - by TravisG
    I want to use hardware filtering to smooth out colors in texels of a texture when I'm accessing texels at coordinates that are not directly at the center of the texel, the catch being that the texels store 2 bands of spherical harmonics coefficients (=4 coefficients), not RGBA intensity values. Can I just use hardware filtering like that (GL_LINEAR with and without mip mapping) without any considerations? In other terms: If I were to first convert the coefficients back to intensity representations, than manually interpolate between two intensities, would the resulting intensity be the same as if I interpolated between the coefficient vectors directly and then converted the interpolated result to intensities?

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  • How can I determine the first visible tile in an isometric perspective?

    - by alekop
    I am trying to render the visible portion of a diamond-shaped isometric map. The "world" coordinate system is a 2D Cartesian system, with the coordinates increasing diagonally (in terms of the view coordinate system) along the axes. The "view" coordinates are simply mouse offsets relative to the upper left corner of the view. My rendering algorithm works by drawing diagonal spans, starting from the upper right corner of the view and moving diagonally to the right and down, advancing to the next row when it reaches the right view edge. When the rendering loop reaches the lower left corner, it stops. There are functions to convert a point from view coordinates to world coordinates and then to map coordinates. Everything works when rendering from tile 0,0, but as the view scrolls around the rendering needs to start from a different tile. I can't figure out how to determine which tile is closest to the upper right corner. At the moment I am simply converting the coordinates of the upper right corner to map coordinates. This works as long as the view origin (upper right corner) is inside the world, but when approaching the edges of the map the starting tile coordinate obviously become invalid. I guess this boils down to asking "how can I find the intersection between the world X axis and the view X axis?"

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  • Java getResourceAsStream as local resource

    - by Dajgoro Labinac
    Before using LWJGL, I used the Graphic method, and there I displayed imageicons, and I had the picture file located in the resources. I used: ImageIcon tcard = new ImageIcon(this.getClass().getResource("RCA.png")); to load the image. Now when I load textures in LWJGL, I have to use absolute paths to locate the file: tcard = TextureLoader.getTexture("PNG", ResourceLoader.getResourceAsStream("C:/RCA.png")); I tried Googling, but I didn't find anything helpful. How can I load the image from the local resources like in the first example?

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