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• Trade offs of linking versus skinning geometry

  - by Jeff

  What are the trade offs between inherent in linking geometry to a node versus using skinned geometry? Specifically: What capabilities do you gain / lose from using each method? What are the performance impacts of doing one over the other? What are the specific situations where you would want to do one over the other? In addition, do the answers to these questions tend to be engine specific? If so, how much?

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• How to fix issue with my 3D first person camera?

  - by dxCUDA

  My camera moves and rotates, but relative to the worlds origin, instead of the players. I am having difficulty rotating the camera and then translating the camera in the direction relative to the camera facing angle. I have been able to translate the camera and rotate relative to the players origin, but not then rotate and translate in the direction relative to the cameras facing direction. My goal is to have a standard FPS-style camera. float yaw, pitch, roll; D3DXMATRIX rotationMatrix; D3DXVECTOR3 Direction; D3DXMATRIX matRotAxis,matRotZ; D3DXVECTOR3 RotAxis; // Set the yaw (Y axis), pitch (X axis), and roll (Z axis) rotations in radians. pitch = m_rotationX * 0.0174532925f; yaw = m_rotationY * 0.0174532925f; roll = m_rotationZ * 0.0174532925f; up = D3DXVECTOR3(0.0f, 1.0f, 0.0f);//Create the up vector //Build eye ,lookat and rotation vectors from player input data eye = D3DXVECTOR3(m_fCameraX, m_fCameraY, m_fCameraZ); lookat = D3DXVECTOR3(m_fLookatX, m_fLookatY, m_fLookatZ); rotation = D3DXVECTOR3(m_rotationX, m_rotationY, m_rotationZ); D3DXVECTOR3 camera[3] = {eye,//Eye lookat,//LookAt up };//Up RotAxis.x = pitch; RotAxis.y = yaw; RotAxis.z = roll; D3DXVec3Normalize(&Direction, &(camera[1] - camera[0]));//Direction vector D3DXVec3Cross(&RotAxis, &Direction, &camera[2]);//Strafe vector D3DXVec3Normalize(&RotAxis, &RotAxis); // Create the rotation matrix from the yaw, pitch, and roll values. D3DXMatrixRotationYawPitchRoll(&matRotAxis, pitch,yaw, roll); //rotate direction D3DXVec3TransformCoord(&Direction,&Direction,&matRotAxis); //Translate up vector D3DXVec3TransformCoord(&camera[2], &camera[2], &matRotAxis); //Translate in the direction of player rotation D3DXVec3TransformCoord(&camera[0], &camera[0], &matRotAxis); camera[1] = Direction + camera[0];//Avoid gimble locking D3DXMatrixLookAtLH(&in_viewMatrix, &camera[0], &camera[1], &camera[2]);

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• Interpolating Matrices

  - by sebf

  Hello, Apologies if I am missing something very obvious (likely!) but is there anything wrong with interpolating between two matrices by: float d = (float)(targetTime.Ticks - keyframe_start.ticks) / (float)(keyframe_end.ticks - keyframe_start.ticks); return ((keyframe_start.Transform * (1 - d)) + (keyframe_end.Transform * d)); As in my app, when I try an use this to interpolate between two keyframes, the model begins to 'shrink' - the severity based on how far between the two keyframes the target time is; its worst when the transform split is ~50/50.

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• Phone crash when try to use vibration on Android

  - by Diego Unanue

  Im developing an app that when you click a button the phone has to vibrate, the issue is that the phone just chashes. Saing that I need permitions to vibrate. I've already set this permition in the build.setting (android manifiest). Here is the code build.settings: settings = { orientation = { default = "portrait", supported = { "portrait", } }, iphone = { plist= { CoronaUseIOS7LandscapeOnlyWorkaround = true, CoronaUseIOS7IPadPhotoPickerLandscapeOnlyWorkaround = true, CoronaUseIOS6LandscapeOnlyWorkaround = true, CoronaUseIOS6IPadPhotoPickerLandscapeOnlyWorkaround = true, UIApplicationExitsOnSuspend = false, UIPrerenderedIcon = true, UIStatusBarHidden = false, CFBundleIconFile = "Icon.png", CFBundleIconFiles = { "Icon.png", "[email protected]", "Icon-60.png", "[email protected]", "Icon-72.png", "[email protected]", "Icon-76.png", "[email protected]", "Icon-Small.png", "[email protected]", "Icon-Small-40.png", "[email protected]", "Icon-Small-50.png", "[email protected]", }, }, }, android = { permissions = { { name = ".permission.C2D_MESSAGE", protectionLevel = "signature" }, }, usesPermissions = { "android.permission.INTERNET", "android.permission.VIBRATE", }, }, } the file that uses the vibration is: local onButtonEvent = function (event ) system.vibrate() end I read all post in Corona page without success. Can I see the android manifest to see if the permissions are there. I've read that is a Corona issue not sure.

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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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• Car engine sound simulation

  - by Petteri Hietavirta

  I have been thinking how to create realistic sound for a car. The main sound is the engine, then all kind of wind, road and suspension sounds. Are there any open source projects for the engine sound simulation? Simply pitching up the sample does not sound too great. The ideal would be to something that allows me to pick type of the engine (i.e. inline-4 vs v-8), add extras like turbo/supercharger whine and finally set the load and rpm. Edit: Something like http://www.sonory.org/examples.html

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• How to fix bad Collada produced by FBX?

  - by David

  I tried to use the FBX SDK (2011.3.1) to load FBX files and save them as Collada files in order to be able to import FBX files in Panda3D. Unfortunately the resulting Collada files are not usable for several reasons, among them: There's a Maya specific extra technique diffuse <diffuse> <texture texture="Map__2-image" texcoord="CHANNEL0"> <extra> <technique profile="MAYA"> <wrapU sid="wrapU0">TRUE</wrapU> <wrapV sid="wrapV0">TRUE</wrapV> <blend_mode>ADD</blend_mode> </technique> </extra> </texture> </diffuse> It assigns a texcoord channel name that isn't referenced anywhere else in the file (in the previous code sample, no geometry uses "CHANNEL0"...) Every polygon is exported twice, a first time with a basic material (only diffuse color, specular color, etc.) and a second time with a textured material -- this doubles the number of polygons of each model without any valuable reason Anyway, the resulting Collada file cannot be opened correctly either with OpenCOLLADA or Panda3D's "dae2egg". Anyone has any experience on how to "fix" it and make it understandable by common and well-reputed Collada importers such as OpenCOLLADA?

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• Rotate sprite to face 3D camera

  - by omikun

  I am trying to rotate a sprite so it is always facing a 3D camera. shaders->setUniform("camera", gCamera.matrix()); glm::mat4 scale = glm::scale(glm::mat4(), glm::vec3(5e5, 5e5, 5e5)); glm::vec3 look = gCamera.position(); glm::vec3 right = glm::cross(gCamera.up(), look); glm::vec3 up = glm::cross(look, right); glm::mat4 newTransform = glm::lookAt(glm::vec3(0), gCamera.position(), up) * scale; shaders->setUniform("model", newTransform); In the vertex shader: gl_Position = camera * model * vec4(vert, 1); The object will track the camera if I move the camera up or down, but if I rotate the camera around it, it will rotate in the other direction so I end up seeing its front twice and its back twice as I rotate around it 360. What am I doing wrong?

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• Most efficient way to rebuild a tree structure from data

  - by Ahsan

  Have a question on recursively populating JsTree using the .NET wrapper available via NuGet. Any help would be greatly appreciated. the .NET class JsTree3Node has a property named Children which holds a list of JsTree3Nodes, and the pre-existing table which contains the node structure looks like this NodeId ParentNodeId Data AbsolutePath 1 NULL News /News 2 1 Financial /News/Financial 3 2 StockMarket /News/Financial/StockMarket I have a EF data context from the the database, so my code currently looks like this. var parentNode = new JsTree3Node(Guid.NewGuid().ToString()); foreach(var nodeItem in context.Nodes) { parentNode.Children.Add(nodeItem.Data); // What is the most efficient logic to do this recursively? } as the inline comment says in the above code, what would be the most efficient way to load the JStree data on to the parentNode object. I can change the existing node table to suite the logic so feel free to suggest any changes to improve performance.

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• How do you author HDR content?

  - by Nathan Reed

  How do you make it easy for your artists to author content for an HDR renderer? What kinds of tools should you provide, and what workflows need to change, in going from LDR to HDR? Note that I'm not asking about the technical aspects of implementing an HDR renderer, but about best practices for creating materials and lighting in HDR. I've googled around a bit, but there doesn't seem to be much about this topic on the web. Can anyone point me to some good resources on this, or share their own experiences? Some specific points: Lighting - how can lighting artists pick HDR light colors? Do they have a standard LDR color picker and then a multiplier? Is the multiplier in gamma or linear space? Maybe instead of a multiplier it's a log-luminance? Or a physical brightness level, like the number of lumens? How will they know what multiplier/luminance/brightness is "correct" for a given light? Materials - how can texture artists make emissive color maps, such as neon signs, TV screens, skyboxes, etc? Can you paint one as a regular LDR (8-bit-per-channel) image and apply a multiplier (or log-luminance, etc.)? Are there cases where it's necessary to actually paint HDR images? If so, how do you go about this in Photoshop (or other software)?

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• How to Export Flash Animation Data

  - by charliep

  I'd love for my partner, the artist, to be able to animate using flash movieclips and timelines. Then I, the programmer, would like to read the raw Flash info and re-program it into my engine of choice (which happens to be Torque2D). The data I'd want is the bitmap images that were used in Flash, like the head and body the links between the images, like where the head connects to the body the motion data from the flash animation, like move, rotate (at what speed), shear, etc. for the head or arms or whatever. Is there any way to get this data? Here's what I know so far. There are tools like SWFSheet and Spriteloq that convert the entire flash animation into a frame by frame sprite animation (in a sprite sheet). This would take too much space in my case, so I'd like to avoid that. Re-animating on the fly would take much less texture memory. There is a PDF that describes the SWF file format but NOT the individual components like the movieclips. So anyone know of a library I can use, or how I can learn more about the movieclip components and whatnot? (more better tags: transform, export, convert)

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• How do I draw a scene with 2 nested frames

  - by Guido Granobles

  I have been trying for long time to figure out this: I have loaded a model from a directx file (I am using opengl and Java) the model have a hierarchical system of nested reference frames (there are not bones). There are just 2 frames, one of them is called x3ds_Torso and it has a child frame called x3ds_Arm_01. Each one of them has a mesh. The thing is that I can't draw the arm connected to the body. Sometimes the body is in the center of the screen and the arm is at the top. Sometimes they are both in the center. I know that I have to multiply the matrix transformation of every frame by its parent frame starting from the top to the bottom and after that I have to multiply every vertex of every mesh by its final transformation matrix. So I have this: public void calculeFinalMatrixPosition(Bone boneParent, Bone bone) { System.out.println("-->" + bone.name); if (boneParent != null) { bone.matrixCombined = bone.matrixTransform.multiply(boneParent.matrixCombined); } else { bone.matrixCombined = bone.matrixTransform; } bone.matrixFinal = bone.matrixCombined; for (Bone childBone : bone.boneChilds) { calculeFinalMatrixPosition(bone, childBone); } } Then I have to multiply every vertex of the mesh: public void transformVertex(Bone bone) { for (Iterator<Mesh> iterator = meshes.iterator(); iterator.hasNext();) { Mesh mesh = iterator.next(); if (mesh.boneName.equals(bone.name)) { float[] vertex = new float[4]; double[] newVertex = new double[3]; if (mesh.skinnedVertexBuffer == null) { mesh.skinnedVertexBuffer = new FloatDataBuffer( mesh.numVertices, 3); } mesh.vertexBuffer.buffer.rewind(); while (mesh.vertexBuffer.buffer.hasRemaining()) { vertex[0] = mesh.vertexBuffer.buffer.get(); vertex[1] = mesh.vertexBuffer.buffer.get(); vertex[2] = mesh.vertexBuffer.buffer.get(); vertex[3] = 1; newVertex = bone.matrixFinal.transpose().multiply(vertex); mesh.skinnedVertexBuffer.buffer.put(((float) newVertex[0])); mesh.skinnedVertexBuffer.buffer.put(((float) newVertex[1])); mesh.skinnedVertexBuffer.buffer.put(((float) newVertex[2])); } mesh.vertexBuffer = new FloatDataBuffer( mesh.numVertices, 3); mesh.skinnedVertexBuffer.buffer.rewind(); mesh.vertexBuffer.buffer.put(mesh.skinnedVertexBuffer.buffer); } } for (Bone childBone : bone.boneChilds) { transformVertex(childBone); } } I know this is not the more efficient code but by now I just want to understand exactly how a hierarchical model is organized and how I can draw it on the screen. Thanks in advance for your help.

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• Separate shaders from HTML file in WebGL

  - by Chris Smith

  I'm ramping up on WebGL and was wondering what is the best way to specify my vertex and fragment shaders. Looking at some tutorials, the shaders are embedded directly in the HTML. (And referenced via an ID.) For example: <script id="shader_1-fs" type="x-shader/x-fragment"> precision highp float; void main(void) { // ... } </script> <script id="shader_1-vs" type="x-shader/x-vertex"> attribute vec3 aVertexPosition; uniform mat4 uMVMatrix; // ... My question is, is it possible to have my shaders referenced in a separate file? (Ideally as plain text.) I presume this is straight forward in JavaScript. Is there essentially a way to do this: var shaderText = LoadRemoteFileOnSever('/shaders/shader_1.txt');

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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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• 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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• Cocos2d-x 3.0 animation frame by frame

  - by Narek

  As I know animations are actions. Now I need to play animation frame by frame. Say I have an animation from N frames. each frame should be played after t delay. Now I want to play animation frame by frame, each frame advance the animation's state. How I can do this? And what about playing actions frame by frame advancing the state in general. I ask because I use ECS, and I deal with frames. P.S. I want to do something like this: Action * a = MoveTo(initialPoint, finalPoint, durationOfAnimation); a->play(0.001 seconds); a->play(0.003 seconds); a->play(0.02 seconds); a->play(0.67 seconds); a->play(0.06 seconds); And see the animation.

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• Can't load vector font in Nuclex Framework

  - by ProgrammerAtWork

  I've been trying to get this to work for the last 2 hours and I'm not getting what I'm doing wrong... I've added Nuclex.TrueTypeImporter to my references in my content and I've added Nuclex.Fonts & Nuclex.Graphics in my main project. I've put Arial-24-Vector.spritefont & Lindsey.spritefont in the root of my content directory. _spriteFont = Content.Load<SpriteFont>("Lindsey"); // works _testFont = Content.Load<VectorFont>("Arial-24-Vector"); // crashes I get this error on the _testFont line: File contains Microsoft.Xna.Framework.Graphics.SpriteFont but trying to load as Nuclex.Fonts.VectorFont. So I've searched around and by the looks of it it has something to do with the content importer & the content processor. For the content importer I have no new choices, so I leave it as it is, Sprite Font Description - XNA Framework for content processor and I select Vector Font - Nuclex Framework And then I try to run it. _testFont = Content.Load<VectorFont>("Arial-24-Vector"); // crashes again I get the following error Error loading "Arial-24-Vector". It does work if I load a sprite, so it's not a pathing problem. I've checked the samples, they do work, but I think they also use a different version of the XNA framework because in my version the "Content" class starts with a capital letter. I'm at a loss, so I ask here. Edit: Something super weird is going on. I've just added the following two lines to a method inside FreeTypeFontProcessor::FreeTypeFontProcessor( Microsoft::Xna::Framework::Content::Pipeline::Graphics::FontDescription ^fontDescription, FontHinter hinter, just to check if code would even get there: System::Console::WriteLine("I AM HEEREEE"); System::Console::ReadLine(); So, I compile it, put it in my project, I run it and... it works! What the hell?? This is weird because I've downloaded the binaries, they didn't work, I've compiled the binaries myself. didn't work either, but now I make a small change to the code and it works? _. So, now I remove the two lines, compile it again and it works again. Someone care to elaborate what is going on? Probably some weird caching problem!

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• Changing Palette for Day/Light Mode using GIMP

  - by J.C.

  Hello, Suppose I've a picture, which want to achieve day/light mode by changing 8bpp color palette. If I want the pixel index of my picture is always fixed for both day mode and night mode. For example, the 1st pixel index is 100. Which I can look up index 100 in day mode palette and night mode palette. How can I use GIMP to do so? My goal is to not update my pixel index of my picture. Also, as you see in two palette, they are not one one mapping. That is index 1 of the day mode palette and index 1 of the night mode palette may not used in the same pixel of the picture, how can I tackle this problem? Actually, my use case is as follow I want to use one 8bpp picture to achieve day/night mode by update only the color palette (without updating the pixel index). The advantage is I only have to prepare 2 256 byte palette rather than saving 2 big pictures in my limited data ram. Thanks a lot

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• Loading a new instance of a class through XML not working quite right

  - by Thegluestickman

  I'm having trouble with XML and XNA. I want to be able to load weapon settings through XML to make my weapons easier to make and to have less code in the actual project file. So I started out making a basic XML document, something to just assign variables with. But no matter what I changed it gave me a new error every time. The code below gives me a "XML element 'Tag' not found", I added and it started to say the variables weren't found. What I wanted to do in the XML file as well, was load a texture for the file too. So I created a static class to hold my texture values, then in the Texture tag of my XML document I would set it to that instance too. I think that's were the problems are occuring because that's where the "XML element 'Tag' not found" error is pointing me too. My XML document: <XnaContent> <Asset Type="ConversationEngine.Weapon"> <weaponStrength>0</weaponStrength> <damageModifiers>0</damageModifiers> <speed>0</speed> <magicDefense>0</magicDefense> <description>0</description> <identifier>0</identifier> <weaponTexture>LoadWeaponTextures.ironSword</weaponTexture> </Asset> </XnaContent> My Class to load the weapon XML: public static class LoadWeaponXML { static Weapon Weapons; public static Weapon WeaponLoad(ContentManager content, int id) { Weapons = content.Load<Weapon>(@"Weapons/" + id); return Weapons; } } public static class LoadWeaponTextures { public static Texture2D ironSword; public static void TextureLoad(ContentManager content) { ironSword = content.Load<Texture2D>("Sword"); } } I'm not entirely sure if you can load textures through XML, but any help would be greatly appreciated.

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• Matrix rotation of a rectangle to "face" a given point in 2d

  - by justin.m.chase

  Suppose you have a rectangle centered at point (0, 0) and now I want to rotate it such that it is facing the point (100, 100), how would I do this purely with matrix math? To give some more specifics I am using javascript and canvas and I may have something like this: var position = {x : 0, y: 0 }; var destination = { x : 100, y: 100 }; var transform = Matrix.identity(); this.update = function(state) { // update transform to rotate to face destination }; this.draw = function(ctx) { ctx.save(); ctx.transform(transform); // a helper that just calls setTransform() ctx.beginPath(); ctx.rect(-5, -5, 10, 10); ctx.fillStyle = 'Blue'; ctx.fill(); ctx.lineWidth = 2; ctx.stroke(); ctx.restore(); } Feel free to assume any matrix function you need is available.

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• Transform between two 3d cartesian coordinate systems

  - by Pris

  I'd like to know how to get the rotation matrix for the transformation from one cartesian coordinate system (X,Y,Z) to another one (X',Y',Z'). Both systems are defined with three orthogonal vectors as one would expect. No scaling or translation occurs. I'm using OpenSceneGraph and it offers a Matrix convenience class, if it makes finding the matrix easier: http://www.openscenegraph.org/documentation/OpenSceneGraphReferenceDocs/a00403.html.

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• Why isn't my lighting working properly? Are my normals messed up?

  - by Radek Slupik

  I'm relatively new to OpenGL and I am trying to draw a 3D model (loaded from a 3ds file using lib3ds) using OpenGL with lighting, but about half of it is drawn in black. I set up the light as such: glEnable(GL_LIGHTING); glShadeModel(GL_SMOOTH); GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f}; glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor); glEnable(GL_LIGHT0); GLfloat lightColor0[] = {1.0f, 1.0f, 1.0f, 1.0f}; GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 0.0f}; glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0); glLightfv(GL_LIGHT0, GL_POSITION, lightPos0); The model is in a VBO and drawn using glDrawArrays. The normals are in a separate VBO, and the normals are calculated using lib3ds_mesh_calculate_vertex_normals: std::vector<std::array<float, 3>> normals; for (std::size_t i = 0; i < model->nmeshes; ++i) { auto& mesh = *model->meshes[i]; std::vector<float[3]> vertex_normals(mesh.nfaces * 3); lib3ds_mesh_calculate_vertex_normals(&mesh, vertex_normals.data()); for (std::size_t j = 0; j < mesh.nfaces; ++j) { auto& face = mesh.faces[j]; normals.push_back(make_array(vertex_normals[j])); } } glBindBuffer(GL_ARRAY_BUFFER, normal_vbo_); glBufferData(GL_ARRAY_BUFFER, normals.size() * sizeof(decltype(normals)::value_type), normals.data(), GL_STATIC_DRAW); The problem isn't the vertices; the model is drawn correctly when drawing it as a wireframe. I also fixed the normals in Blender using controlN. What could be the problem? Should I store the normals in a different order?

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• SFML programs fails to debug with glslDevil

  - by Zhen

  I'm testing the glslDevil debugger with a simple (and working) SFML application in Linux + NVidia. But it always fails in the window creation step: W! Program Start | glXGetConfig(0x86a50b0, 0x86acef8, 4, 0xbf8228c4) | glXGetConfig(0x86a50b0, 0x86acef8, 5, 0xbf8228c8) | glXGetConfig(0x86a50b0, 0x86acef8, 8, 0xbf8228cc) | glXGetConfig(0x86a50b0, 0x86acef8, 9, 0xbf8228d0) | glXGetConfig(0x86a50b0, 0x86acef8, 10, 0xbf8228d4) | glXGetConfig(0x86a50b0, 0x86acef8, 11, 0xbf8228d8) | glXGetConfig(0x86a50b0, 0x86acef8, 12, 0xbf8228dc) | glXGetConfig(0x86a50b0, 0x86acef8, 13, 0xbf8228e0) | glXGetConfig(0x86a50b0, 0x86acef8, 100000, 0xbf8228e4) | glXGetConfig(0x86a50b0, 0x86acef8, 100001, 0xbf8228e8) | glXCreateContext(0x86a50b0, 0x86acef8, (nil), 1) E! Child process exited W! Program termination forced! And the code that fails: #include <SFML/Graphics.hpp> #define GL_GLEXT_PROTOTYPES 1 #define GL3_PROTOTYPES 1 #include <GL/gl.h> #include <GL/glu.h> #include <GL/glext.h> int main(){ sf::RenderWindow window{ sf::VideoMode(800, 600), "Test SFML+GL" }; bool running = true; while( running ){ sf::Event event; while( window.pollEvent(event) ){ if( event.type == sf::Event::Closed ){ running = false; }else if(event.type == sf::Event::Resized){ glViewport(0, 0, event.size.width, event.size.height); } } window.display(); } return 0; } Is It posible to solve this problem? or get around the problem to continue the gslsDevil use?.

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• How do I load a libGDX Skin on Android?

  - by Lukas

  I am pretty desperate searching for a solution to load ui skins into my android app (actually it is not my app, it is a tutorial I'm following). The app always crashes at this part: assets.load("ui/defaultskin/defaultskin.json", Skin.class, new SkinLoader.SkinParameter("ui/defaultskin/defaultskin.atlas")); The files are the ones from the bitowl tutorial: http://bitowl.de/day6/ I guess Gdx.files.internal doesn't work on android, since the app crashed with this, too. Thanks for helping me out, Lukas

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• Setting up cube map texture parameters in OpenGL

  - by KaiserJohaan

  I see alot of tutorials and sources use the following code snippet when defining each face of a cube map: for (i = 0; i < 6; i++) glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, InternalFormat, size, size, 0, Format, Type, NULL); Is it safe to assume GL_TEXTURE_CUBE_MAP_POSITIVE_X + i will properly iterate the following cube map targets, GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y etc?

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