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• Quaternion dfference + time --> angular velocity (gyroscope in physics library)

  - by AndrewK

  I am using Bullet Physic library to program some function, where I have difference between orientation from gyroscope given in quaternion and orientation of my object, and time between each frame in milisecond. All I want is set the orientation from my gyroscope to orientation of my object in 3D space. But all I can do is set angular velocity to my object. I have orientation difference and time, and from that I calculate vector of angular velocity [Wx,Wy,Wz] from that formula: W(t) = 2 * dq(t)/dt * conj(q(t)) My code is: btQuaternion diffQuater = gyroQuater - boxQuater; btQuaternion conjBoxQuater = gyroQuater.inverse(); btQuaternion velQuater = ((diffQuater * 2.0f) / d_time) * conjBoxQuater; And everything works well, till I get: 1 rotating around Y axis, angle about 60 degrees, then I have these values in 2 critical frames: x: -0.013220 y: -0.038050 z: -0.021979 w: -0.074250 - diffQuater x: 0.120094 y: 0.818967 z: 0.156797 w: -0.538782 - gyroQuater x: 0.133313 y: 0.857016 z: 0.178776 w: -0.464531 - boxQuater x: 0.207781 y: 0.290452 z: 0.245594 - diffQuater -> euler angles x: 3.153619 y: -66.947929 z: 175.936615 - gyroQuater -> euler angles x: 4.290697 y: -57.553043 z: 173.320053 - boxQuater -> euler angles x: 0.138128 y: 2.823307 z: 1.025552 w: 0.131360 - velQuater d_time: 0.058000 x: 0.211020 y: 1.595124 z: 0.303650 w: -1.143846 - diffQuater x: 0.089518 y: 0.771939 z: 0.144527 w: -0.612543 - gyroQuater x: -0.121502 y: -0.823185 z: -0.159123 w: 0.531303 - boxQuater x: nan y: nan z: nan - diffQuater -> euler angles x: 2.985240 y: -76.304405 z: -170.555054 - gyroQuater -> euler angles x: 3.269681 y: -65.977966 z: 175.639420 - boxQuater -> euler angles x: -0.730262 y: -2.882153 z: -1.294721 w: 63.325996 - velQuater d_time: 0.063000 2 rotating around X axis, angle about 120 degrees, then I have these values in 2 critical frames: x: -0.013045 y: -0.004186 z: -0.005667 w: -0.022482 - diffQuater x: -0.848030 y: -0.187985 z: 0.114400 w: 0.482099 - gyroQuater x: -0.834985 y: -0.183799 z: 0.120067 w: 0.504580 - boxQuater x: 0.036336 y: 0.002312 z: 0.020859 - diffQuater -> euler angles x: -113.129463 y: 0.731925 z: 25.415056 - gyroQuater -> euler angles x: -110.232368 y: 0.860897 z: 25.350458 - boxQuater -> euler angles x: -0.865820 y: -0.456086 z: 0.034084 w: 0.013184 - velQuater d_time: 0.055000 x: -1.721662 y: -0.387898 z: 0.229844 w: 0.910235 - diffQuater x: -0.874310 y: -0.200132 z: 0.115142 w: 0.426933 - gyroQuater x: 0.847352 y: 0.187766 z: -0.114703 w: -0.483302 - boxQuater x: -144.402298 y: 4.891629 z: 71.309158 - diffQuater -> euler angles x: -119.515343 y: 1.745076 z: 26.646086 - gyroQuater -> euler angles x: -112.974533 y: 0.738675 z: 25.411509 - boxQuater -> euler angles x: 2.086195 y: 0.676526 z: -0.424351 w: 70.104248 - velQuater d_time: 0.057000 2 rotating around Z axis, angle about 120 degrees, then I have these values in 2 critical frames: x: -0.000736 y: 0.002812 z: -0.004692 w: -0.008181 - diffQuater x: -0.003829 y: 0.012045 z: -0.868035 w: 0.496343 - gyroQuater x: -0.003093 y: 0.009232 z: -0.863343 w: 0.504524 - boxQuater x: -0.000822 y: -0.003032 z: 0.004162 - diffQuater -> euler angles x: -1.415189 y: 0.304210 z: -120.481873 - gyroQuater -> euler angles x: -1.091881 y: 0.227784 z: -119.399445 - boxQuater -> euler angles x: 0.159042 y: 0.169228 z: -0.754599 w: 0.003900 - velQuater d_time: 0.025000 x: -0.007598 y: 0.024074 z: -1.749412 w: 0.968588 - diffQuater x: -0.003769 y: 0.012030 z: -0.881377 w: 0.472245 - gyroQuater x: 0.003829 y: -0.012045 z: 0.868035 w: -0.496343 - boxQuater x: -5.645197 y: 1.148993 z: -146.507187 - diffQuater -> euler angles x: -1.418294 y: 0.270319 z: -123.638245 - gyroQuater -> euler angles x: -1.415183 y: 0.304208 z: -120.481873 - boxQuater -> euler angles x: 0.017498 y: -0.013332 z: 2.040073 w: 148.120056 - velQuater d_time: 0.027000 The problem is the most visible in diffQuater - euler angles vector. Can someone tell me why it is like that? and how to solve that problem? All suggestions are welcome.

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• Restoring projection matrix

  - by brainydexter

  I am learning to use FBOs and one of the things that I need to do when rendering something onto user defined FBO, I have to setup the projection, modelview and viewport for it. Once I am done rendering to the FBO, I need to restore these matrices. I found: glPushAttrib(GL_VIEWPORT_BIT); glPopAttrib(); to restore the viewport to its old state. Is there a way to restore the projection and modelview matrix to whatever it was earlier ? Tech: C++/OpenGL Thanks!

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• Box2D Bicycle Wheels Motor Problem - Flash 2.1a

  - by Craig

  I have made a bicycle with Box2D using several polygons for the frame at different angles connected using weld joints, and I have revolute joints on the wheels with a motor. I have made some basic terrain (straight ground and a small ramp) and added keyboard input to control the bicycle with torque to balance it. All of this is done in with Box2D's Debug Draw. When the bicycle is on its back wheel but diagonally forward (kinda like this position - /) the motors just cause it go spinning backwards over when in reality it should either stay on its back wheel or go down onto both wheels. Here's my code the revolute joints: //Front Wheel Joint var frontWheelJointDef:b2RevoluteJointDef = new b2RevoluteJointDef(); frontWheelJointDef.Initialize(frontWheelBody, secondFrameBody, frontWheelBody.GetWorldCenter()); frontWheelJointDef.enableMotor=true; frontWheelJointDef.maxMotorTorque=10000; frontWheelJoint = _world.CreateJoint(frontWheelJointDef) as b2RevoluteJoint; //Rear Wheel Joint var rearWheelJointDef:b2RevoluteJointDef = new b2RevoluteJointDef(); rearWheelJointDef.Initialize(rearWheelBody, firstFrameBody, rearWheelBody.GetWorldCenter()); rearWheelJointDef.enableMotor=true; rearWheelJointDef.maxMotorTorque=10000; rearWheelJoint = _world.CreateJoint(rearWheelJointDef) as b2RevoluteJoint; And here's the relevant part of my update function: // up and down control wheels motor if (up) { motorSpeed-=0.5; } if (down) { motorSpeed += 0.5; } // left and right control cart torque if (left) { middleCentreFrameBody.ApplyTorque( -3); gearBody.ApplyTorque( -3); firstFrameBody.ApplyTorque( -3); secondFrameBody.ApplyTorque( -3); rearWheelToChainBody.ApplyTorque( -3); chainToFrontFrameBody.ApplyTorque( -3); topMiddleFrameBody.ApplyTorque( -3); } if (right) { middleCentreFrameBody.ApplyTorque( 3); gearBody.ApplyTorque( 3); firstFrameBody.ApplyTorque( 3); secondFrameBody.ApplyTorque( 3); rearWheelToChainBody.ApplyTorque( 3); chainToFrontFrameBody.ApplyTorque( 3); topMiddleFrameBody.ApplyTorque( 3); } // motor friction motorSpeed*=0.99; // motor max speed if (motorSpeed>100) { motorSpeed=100; } rearWheelJoint.SetMotorSpeed(motorSpeed); frontWheelJoint.SetMotorSpeed(motorSpeed); Any ideas what might be causing this? Thanks

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• Normal map applied as diffuse textures looks wrong

  - by KaiserJohaan

  Diffuse textures works fine, but I am having problem with normal maps, so I thought I'd tried to apply the normal maps as the diffuse map in my fragment shader so I could see everything is OK. I comment-out my normal map code and just set the diffuse map to the normal map and I get this: http://postimg.org/image/j9gudjl7r/ Looks like a smurf! This is the actual normal map of the main body: http://postimg.org/image/sbkyr6fg9/ Here is my fragment shader, notice I commented out normal map code so I could debug the normal map as a diffuse texture "#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"; Here is my wrapper around a texture OpenGLTexture::OpenGLTexture(const std::vector<uint8_t>& textureData, uint32_t textureWidth, uint32_t textureHeight, TextureFormat textureFormat, 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); GLint glTextureFormat = (textureFormat == TextureFormat::TEXTURE_FORMAT_RGB ? GL_RGB : textureFormat == TextureFormat::TEXTURE_FORMAT_RGBA ? GL_RGBA : GL_RED); glTexImage2D(GL_TEXTURE_2D, 0, glTextureFormat, 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); } OpenGLTexture::~OpenGLTexture() { glDeleteBuffers(1, &mTexture); CHECK_GL_ERROR(mLogger); } And here is the sampler I create which is shared between Diffuse and normal textures // texture sampler setup glGenSamplers(1, &mTextureSampler); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_WRAP_S, GL_REPEAT); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_WRAP_T, GL_REPEAT); CHECK_GL_ERROR(mLogger); glSamplerParameterf(mTextureSampler, GL_TEXTURE_MAX_ANISOTROPY_EXT, mCurrentAnisotropy); CHECK_GL_ERROR(mLogger); glUniform1i(glGetUniformLocation(mDefaultProgram.GetHandle(), "unifDiffuseTexture"), OpenGLTexture::TEXTURE_UNIT_DIFFUSE); CHECK_GL_ERROR(mLogger); glUniform1i(glGetUniformLocation(mDefaultProgram.GetHandle(), "unifNormalTexture"), OpenGLTexture::TEXTURE_UNIT_NORMAL); CHECK_GL_ERROR(mLogger); glBindSampler(OpenGLTexture::TEXTURE_UNIT_DIFFUSE, mTextureSampler); CHECK_GL_ERROR(mLogger); glBindSampler(OpenGLTexture::TEXTURE_UNIT_NORMAL, mTextureSampler); CHECK_GL_ERROR(mLogger); SetAnisotropicFiltering(mCurrentAnisotropy); The diffuse textures looks like they should, but the normal looks so wierd. Why is this?

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• running GL ES 2.0 code under Linux ( no Android no iOS )

  - by user827992

  I need to code OpenGL ES 2.0 bits and i would like to do this and run the programs on my desktop for practical reasons. Now, i already have tried the official GLES SDK from ATI for my videocard but it not even runs the examples that comes with the SDK itself, i'm not looking for performance here, even a software based rendering pipeline could be enough, i just need full support for GLES 2.0 and GLSL to code and run GL stuff. There is a reliable solution for this under Ubuntu Linux ?

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• "Accumulate" buffer results in XNA4?

  - by Utkarsh Sinha

  I'm trying to simulate a "heightmap" buffer in XNA4.0 but the results don't look correct. Here's what I'm hoping to achieve: http://www.youtube.com/watch?feature=player_detailpage&v=-Q6ISVaM5Ww#t=517s (8:38). From what I understand, here are the steps to reach there: Pass height buffer + current entity's heightmap Generate a stencil and update the height buffer Render sprite+stencil For now, I'm just trying to get the height buffer thing to work. So here's the problem. Inside the draw loop, I do the following: Create a new render target & set it Draw the heightmap with a sprite batch(no shaders) graphicsDevice.SetRenderTarget(null) Draw the rendertarget with SpriteBatch I expected to see all entities' heightmaps. But only the last entity's heightmap is visible. Any hints on what I'm doing wrong? Here's the code inside the draw loop: RenderTarget2D tempDepthStencil = new RenderTarget2D(graphicsDevice, graphicsDevice.Viewport.Width, graphicsDevice.Viewport.Height, false, graphicsDevice.DisplayMode.Format, DepthFormat.None); graphicsDevice.SetRenderTarget(tempDepthStencil); // Gather depth information SpriteBatch depthStencilSpriteBatch = new SpriteBatch(graphicsDevice); depthStencilSpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.None, RasterizerState.CullCounterClockwise); depthStencilSpriteBatch.Draw(texHeightmap, pos, null, Color.White, 0, Vector2.Zero, 1, spriteEffects, 1); depthStencilSpriteBatch.End(); graphicsDevice.SetRenderTarget(null); SpriteBatch b1 = new SpriteBatch(graphicsDevice); b1.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, null, null, null, null); b1.Draw((Texture2D)tempDepthStencil, Vector2.Zero, null, Color.White, 0, Vector2.Zero, 1, spriteEffects, 1); b1.End();

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• How to make unit selection circles merge?

  - by MaT

  I would like to know how to make this effect of merged circle selection. Here are images to illustrate: Basically I'm looking for this effect: How the merge effect of the circles can be achieved ? I didn't found any explanation concerning this effect. I know that to project those texture I can develop a decal system but I don't know how to create the merging effect. If possible, I'm looking for purely shaders solution.

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• CSM shadow errors when models are split

  - by KaiserJohaan

  I'm getting closer to fixing CSM, but there seems to be one more issue at hand. At certain angles, the models will be caught/split between two shadow map cascades, like below. first depth split second depth split - here you can see the model is caught between the splits How does one fix this? Increase the overlapping boundaries between the splits? Or is the frustrum erronous? CameraFrustrum CalculateCameraFrustrum(const float fovDegrees, const float aspectRatio, const float minDist, const float maxDist, const Mat4& cameraViewMatrix, Mat4& outFrustrumMat) { CameraFrustrum ret = { Vec4(1.0f, -1.0f, 0.0f, 1.0f), Vec4(1.0f, 1.0f, 0.0f, 1.0f), Vec4(-1.0f, 1.0f, 0.0f, 1.0f), Vec4(-1.0f, -1.0f, 0.0f, 1.0f), Vec4(1.0f, -1.0f, 1.0f, 1.0f), Vec4(1.0f, 1.0f, 1.0f, 1.0f), Vec4(-1.0f, 1.0f, 1.0f, 1.0f), Vec4(-1.0f, -1.0f, 1.0f, 1.0f), }; const Mat4 perspectiveMatrix = PerspectiveMatrixFov(fovDegrees, aspectRatio, minDist, maxDist); const Mat4 invMVP = glm::inverse(perspectiveMatrix * cameraViewMatrix); outFrustrumMat = invMVP; for (Vec4& corner : ret) { corner = invMVP * corner; corner /= corner.w; } return ret; } Mat4 CreateDirLightVPMatrix(const CameraFrustrum& cameraFrustrum, const Vec3& lightDir) { Mat4 lightViewMatrix = glm::lookAt(Vec3(0.0f), -glm::normalize(lightDir), Vec3(0.0f, -1.0f, 0.0f)); Vec4 transf = lightViewMatrix * cameraFrustrum[0]; float maxZ = transf.z, minZ = transf.z; float maxX = transf.x, minX = transf.x; float maxY = transf.y, minY = transf.y; for (uint32_t i = 1; i < 8; i++) { transf = lightViewMatrix * cameraFrustrum[i]; if (transf.z > maxZ) maxZ = transf.z; if (transf.z < minZ) minZ = transf.z; if (transf.x > maxX) maxX = transf.x; if (transf.x < minX) minX = transf.x; if (transf.y > maxY) maxY = transf.y; if (transf.y < minY) minY = transf.y; } Mat4 viewMatrix(lightViewMatrix); viewMatrix[3][0] = -(minX + maxX) * 0.5f; viewMatrix[3][1] = -(minY + maxY) * 0.5f; viewMatrix[3][2] = -(minZ + maxZ) * 0.5f; viewMatrix[0][3] = 0.0f; viewMatrix[1][3] = 0.0f; viewMatrix[2][3] = 0.0f; viewMatrix[3][3] = 1.0f; Vec3 halfExtents((maxX - minX) * 0.5, (maxY - minY) * 0.5, (maxZ - minZ) * 0.5); return OrthographicMatrix(-halfExtents.x, halfExtents.x, halfExtents.y, -halfExtents.y, halfExtents.z, -halfExtents.z) * viewMatrix; }

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• Algorithm to find average position

  - by Simran kaur

  In the given diagram, I have the extreme left and right points, that is -2 and 4 in this case. So, obviously, I can calculate the width which is 6 in this case. What we know: The number of partitions:3 in this case The partition number at at any point i.e which one is 1st,second or third partition (numbered starting from left) What I want: The position of the purple line drawn which is positio of average of a particular partition So, basically I just want a generalized formula to calculate position of the average at any point.

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• Early Z culling - Ogre

  - by teodron

  This question is concerned with how one can enable this "pixel filter" to work within an Ogre based app. Simply put, one can write two passes, the first without writing any colour values to the frame buffer lighting off colour_write off shading flat The second pass is the one that employs heavy pixel shader computations, hence it would be really nice to get rid of those hidden surface patches and not process them pixel-wise. This approach works, except for one thing: objects with alpha, such as billboard trees suffer in a peculiar way - from one side, they seem to capture the sky/background within their alpha region and ignore other trees/houses behind them, while viewed from the other side, they exhibit the desired behavior. To tackle the issue, I thought I could write a custom vertex shader in the first pass and offset the projected Z component of the vertex a little further away from its actual position, so that in the second pass there is a need to recompute correctly the pixels of the objects closest to the camera. This doesn't work at all, all surfaces are processed in the pixel shader and there is no performance gain. So, if anyone has done a similar trick with Ogre and alpha objects, kindly please help.

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• Automated texture mapping

  - by brandon

  I have a set of seamless tiling textures. I want to be able to take an arbitrary model and create a UV map with these properties: No stretching (all textures tile appropriately so there is no stretching and sheering of the texture) The textures display on the correct axis relative to the model it's mapping to (if you look at the example, you can see some of the letters on the front are tilted, the y axis of the texture should be matching up with the y axis of the object. Some other faces have upside down letters too) the texture is as continuous as possible on the surface of the model (if two faces are adjacent, the texture continues on the adjacent face where it left off) the model is closed (all faces are completely enclosed by other faces) A few notes. This mapping will occur before triangulation. I realize there are ways to do this by hand and it's probably a hard problem to automatically map textures in general, but since these textures are seamless and I just need uniform coverage it seems like an easier problem. I'm looking for an algorithmic approach to this that I can apply in general, not a tool that does it. What approach would work for this, is there an existing one? (I assume so)

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• Unexpected behaviour with glFramebufferTexture1D

  - by Roshan

  I am using render to texture concept with glFramebufferTexture1D. I am drawing a cube on non-default FBO with all the vertices as -1,1 (maximum) in X Y Z direction. Now i am setting viewport to X while rendering on non default FBO. My background is blue with white color of cube. For default FBO, i have created 1-D texture and attached this texture to above FBO with color attachment. I am setting width of texture equal to width*height of above FBO view-port. Now, when i render this texture to on another cube, i can see continuous white color on start or end of each face of the cube. That means part of the face is white and rest is blue. I am not sure whether this behavior is correct or not. I expect all the texels should be white as i am using -1 and 1 coordinates for cube rendered on non-default FBO. code: #define WIDTH 3 #define HEIGHT 3 GLfloat vertices8[]={ 1.0f,1.0f,1.0f, -1.0f,1.0f,1.0f, -1.0f,-1.0f,1.0f, 1.0f,-1.0f,1.0f,//face 1 1.0f,-1.0f,-1.0f, -1.0f,-1.0f,-1.0f, -1.0f,1.0f,-1.0f, 1.0f,1.0f,-1.0f,//face 2 1.0f,1.0f,1.0f, 1.0f,-1.0f,1.0f, 1.0f,-1.0f,-1.0f, 1.0f,1.0f,-1.0f,//face 3 -1.0f,1.0f,1.0f, -1.0f,1.0f,-1.0f, -1.0f,-1.0f,-1.0f, -1.0f,-1.0f,1.0f,//face 4 1.0f,1.0f,1.0f, 1.0f,1.0f,-1.0f, -1.0f,1.0f,-1.0f, -1.0f,1.0f,1.0f,//face 5 -1.0f,-1.0f,1.0f, -1.0f,-1.0f,-1.0f, 1.0f,-1.0f,-1.0f, 1.0f,-1.0f,1.0f//face 6 }; GLfloat vertices[]= { 0.5f,0.5f,0.5f, -0.5f,0.5f,0.5f, -0.5f,-0.5f,0.5f, 0.5f,-0.5f,0.5f,//face 1 0.5f,-0.5f,-0.5f, -0.5f,-0.5f,-0.5f, -0.5f,0.5f,-0.5f, 0.5f,0.5f,-0.5f,//face 2 0.5f,0.5f,0.5f, 0.5f,-0.5f,0.5f, 0.5f,-0.5f,-0.5f, 0.5f,0.5f,-0.5f,//face 3 -0.5f,0.5f,0.5f, -0.5f,0.5f,-0.5f, -0.5f,-0.5f,-0.5f, -0.5f,-0.5f,0.5f,//face 4 0.5f,0.5f,0.5f, 0.5f,0.5f,-0.5f, -0.5f,0.5f,-0.5f, -0.5f,0.5f,0.5f,//face 5 -0.5f,-0.5f,0.5f, -0.5f,-0.5f,-0.5f, 0.5f,-0.5f,-0.5f, 0.5f,-0.5f,0.5f//face 6 }; GLuint indices[] = { 0, 2, 1, 0, 3, 2, 4, 5, 6, 4, 6, 7, 8, 9, 10, 8, 10, 11, 12, 15, 14, 12, 14, 13, 16, 17, 18, 16, 18, 19, 20, 23, 22, 20, 22, 21 }; GLfloat texcoord[] = { 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0 }; glGenTextures(1, &id1); glBindTexture(GL_TEXTURE_1D, id1); glGenFramebuffers(1, &Fboid); glTexParameterf(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameterf(GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameterf(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexImage1D(GL_TEXTURE_1D, 0, GL_RGBA, WIDTH*HEIGHT , 0, GL_RGBA, GL_UNSIGNED_BYTE,0); glBindFramebuffer(GL_FRAMEBUFFER, Fboid); glFramebufferTexture1D(GL_DRAW_FRAMEBUFFER,GL_COLOR_ATTACHMENT0,GL_TEXTURE_1D,id1,0); draw_cube(); glBindFramebuffer(GL_FRAMEBUFFER, 0); draw(); } draw_cube() { glViewport(0, 0, WIDTH, HEIGHT); glClearColor(0.0f, 0.0f, 0.5f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); glEnableVertexAttribArray(glGetAttribLocation(temp.psId,"position")); glVertexAttribPointer(glGetAttribLocation(temp.psId,"position"), 3, GL_FLOAT, GL_FALSE, 0,vertices8); glDrawArrays (GL_TRIANGLE_FAN, 0, 24); } draw() { glClearColor(1.0f, 0.0f, 0.0f, 1.0f); glClearDepth(1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnableVertexAttribArray(glGetAttribLocation(shader_data.psId,"tk_position")); glVertexAttribPointer(glGetAttribLocation(shader_data.psId,"tk_position"), 3, GL_FLOAT, GL_FALSE, 0,vertices); nResult = GL_ERROR_CHECK((GL_NO_ERROR, "glVertexAttribPointer(position, 3, GL_FLOAT, GL_FALSE, 0,vertices);")); glEnableVertexAttribArray(glGetAttribLocation(shader_data.psId,"inputtexcoord")); glVertexAttribPointer(glGetAttribLocation(shader_data.psId,"inputtexcoord"), 2, GL_FLOAT, GL_FALSE, 0,texcoord); glBindTexture(*target11, id1); glDrawElements ( GL_TRIANGLES, 36,GL_UNSIGNED_INT, indices ); when i change WIDTH=HEIGHT=2, and call a glreadpixels with height, width equal to 4 in draw_cube() i can see first 2 pixels with white color, next two with blue(glclearcolor), next two white and then blue and so on.. Now when i change width parameter in glTeximage1D to 16 then ideally i should see alternate patches of white and blue right? But its not the case here. why so?

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• How to efficiently render resizable GUI elements in DirectX?

  - by PolGraphic

  I wonder what would be most efficient way to render the GUI elements. When we're talking about constant-size elements (that can still be moving), the textures' atlas seems to be good. But what with the resizeable elements? Let's say the panel (with textured borders)? Is there any better way than just render 9 rectangles with textures on them (I guess one texture and different textures coordinates for left-top corner, border, middle etc. used in shader)?

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• Sprite not rotating around its centre after Scaling at its centre

  - by asma.farhat

  If I scale a sprite at its centre, then try to rotate it around its centre as well, the rotation does not occur around its centre. If you need to rotate, for example a scaled ball,the way its working it is set the scale center at the top left (0,0) set the scale that you want, and then set the rotation center to the middle of the scaled sprite, and then apply the rotation modifier. blaBloBliSprite.setScaleCenter(0, 0); blaBloBliSprite.setScale(0.667f); blaBloBliSprite.setPosition(557, CAMERA_HEIGHT / 2 - blaBloBliSprite.getHeightScaled() / 2); blaBloBliSprite.setRotationCenter(blaBloBliSprite.getWidthScaled() / 2, blaBloBliSprite.getHeightScaled() / 2); But I want to scale a sprite at its centre as well. Is there any way of doing it?

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• Effective way to check if an Entity/Player enters a region/trigger

  - by Chris

  I was wondering how multiplayer games detect if you enter a special region. Let's assume there is a huge map that is so big that simply checking it would become a huge performance issue. I've seen bukkit (a modding API for Minecraft servers) firing an Event on every single move. I don't think that larger games do the same because even if you have only a few coordinates you are interested in, you have to loop through a few trigger zone to see if the player is inside your region - for every player. This seems like an extremely CPU-intense operation to me even though I've never developed something like that. Is there a special algorithm that is used by larger games to accomplish this? The only thing I could imagine is to split up the world into multiple parts and to register the event not on the movement itself but on all the parts that are covered by your area and only check for areas that are registered in the current part. And another thing I would like to know: How could you detect when someone must have entered a trigger but you never saw him directly in it since his client only sent you an move packet shortly before entering and after leaving the trigger area. Drawing a line and calculate all colliding parts seems rather CPU intensive if you have to perform it every time.

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• Raycasting mouse coordinates to rotated object?

  - by SPL

  I am trying to cast a ray from my mouse to a plane at a specified position with a known width and length and height. I know that you can use the NDC (Normalized Device Coordinates) to cast ray but I don't know how can I detect if the ray actually hit the plane and when it did. The plane is translated -100 on the Y and rotated 60 on the X then translated again -100. Can anyone please give me a good tutorial on this? For a complete noob! I am almost new to matrix and vector transformations.

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• Image with FadeIn effect blinks when added to scene

  - by Ef Es

  I am trying to add an image to the scene, but it should just be added to the scene invisible, FadeIn and then be deleted when the effect finishes. My problem is that the images blink once when they are added to the scene, then they do the intended effect. My best guess is that when they are added they show on the scene for a split second before starting the animation. I though of making them invisible for a split second before activating them, but I am not sure how to code it. const bool Sunbeams::add() { const CCSize kSceenSize = CCDirector::sharedDirector()->getWinSize(); const int nRayType = random( m_kRays.size()); const CCPoint kPosition( random( static_cast < int >( kSceenSize.width)), 0.0f); const float fDuration = random( m_fDurationVariance) + m_fDurationMin; CCSprite* pkLightBeam = CCSprite::spriteWithTexture( m_kRays[nRayType]); if ( !pkLightBeam) { msg::debug( "Sunbeams::add", "Failed to create sprite from ray '%d'!\n", m_kRays[nRayType]); return false; } pkLightBeam->setAnchorPoint( CCPointZero); pkLightBeam->setPosition( kPosition); m_kActiveBeams.push_back( pkLightBeam); CCDirector::sharedDirector()->getRunningScene()->addChild( pkLightBeam); CCActionInterval* pkAction = CCFadeIn::actionWithDuration( fDuration); CCActionInterval* pkActionBack = pkAction->reverse(); pkLightBeam->runAction( CCSequence::actions( pkAction, pkActionBack, 0)); return true; }

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• ray collision with rectangle and floating point accuracy

  - by phq

  I'm trying to solve a problem with a ray bouncing on a box. Actually it is a sphere but for simplicity the box dimensions are expanded by the sphere radius when doing the collision test making the sphere a single ray. It is done by projecting the ray onto all faces of the box and pick the one that is closest. However because I'm using floating point variables I fear that the projected point onto the surface might be interpreted as being below in the next iteration, also I will later allow the sphere to move which might make that scenario more likely. Also the bounce coefficient might be as low as zero, making the sphere continue along the surface. So my naive solution is to project not only forwards but backwards to catch those cases. That is where I got into problems shown in the figure: In the first iteration the first black arrow is calculated and we end up at a point on the surface of the box. In the second iteration the "back projection" hits the other surface making the second black arrow bounce on the wrong surface. If there are several boxes close to each other this has further consequences making the sphere fall through them all. So my main question is how to handle possible floating point accuracy when placing the sphere on the box surface so it does not fall through. In writing this question I got the idea to have a threshold to only accept back projections a certain amount much smaller than the box but larger than the possible accuracy limitation, this would only cause the "false" back projection when the sphere hit the box on an edge which would appear naturally. To clarify my original approach, the arrows shown in the image is not only the path the sphere travels but is also representing a single time step in the simulation. In reality the time step is much smaller about 0.05 of the box size. The path traveled is projected onto possible sides to avoid traveling past a thinner object at higher speeds. In normal situations the floating point accuracy is not an issue but there are two situations where I have the concern. When the new position at the end of the time step is located very close to the surface, very unlikely though. When using a bounce factor of 0, here it happens every time the sphere hit a box. To add some loss of accuracy, the motivation for my concern, is that the sphere and box are in different coordinate systems and thus the sphere location is transformed for every test. This last one is why I'm not willing to stand on luck that one floating point value lying on top of the box always will be interpreted the same. I did not know voronoi regions by name, but looking at it I'm not sure how it would be used in a projection scenario that I'm using here.

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• How to make an object stay relative to another object

  - by Nick

  In the following example there is a guy and a boat. They have both a position, orientation and velocity. The guy is standing on the shore and would like to board. He changes his position so he is now standing on the boat. The boat changes velocity and orientation and heads off. My character however has a velocity of 0,0,0 but I would like him to stay onboard. When I move my character around, I would like to move as if the boat was the ground I was standing on. How do keep my character aligned properly with the boat? It is exactly like in World Of Warcraft, when you board a boat or zeppelin. This is my physics code for the guy and boat: this.velocity.addSelf(acceleration.multiplyScalar(dTime)); this.position.addSelf(this.velocity.clone().multiplyScalar(dTime)); The guy already has a reference to the boat he's standing on, and thus knows the boat's position, velocity, orientation (even matrices or quaternions can be used).

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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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• "Unable to create OpenGL 3.3 context (flags 0, profile 1)"

  - by Tsvetan

  Trying to run any of the well-known McKesson's tutorials on a friend's laptop results in the aforementioned exception. I read that in order to run applications which use OpenGL 3.3 you must at least have an ATI HD or Nvidia 8xxx GPU series. He has an ATI HD class graphics processor which eliminates (maybe) this issue. Also, I read that this error may result in having old drivers. He updated his drivers but that didn't solve the problem. The tutorials are built as said in the book introduction and glsdk is installed. If more information is needed, say so and I will provide it. What are the other reasons for this kind of exception? And how can I fix them?

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• What could cause a pixel shader to paint outside the lines of the vertex shader output?

  - by Rei Miyasaka

  From what I understand, the pixels that a pixel shader operates on are specified implicitly by the SV_POSITION output (in DirectX) of the vertex shader. What then could cause a pixel shader to render in the middle of nowhere? I used the new Visual Studio 2012 graphics debugger to visualize my vertex and pixel shader output. This is the output from a DrawIndexed() call that draws a cube: The pink part is the rendered output of the pixel shader, which takes the cube on its left as its input. The vertex shader code: cbuffer Buf { float4x4 final; }; struct In { float4 pos:POSITION; float3 norm:NORMAL; float2 texuv:TEXCOORD; }; struct Out { float4 col:COLOR; float2 tex:TEXCOORD; float4 pos:SV_POSITION; }; Out main(In input) { Out output; output.pos = mul(input.pos, final); output.col = float4(1.0f, 0.5f, 0.5f, 1.0f); output.tex = input.texuv; return output; } And the pixel shader: struct In { float4 col:COLOR; float2 tex:TEXCOORD; float4 pos:SV_POSITION; }; float4 main(In input) : SV_TARGET { return input.col; } The raster stage is the only thing between the vertex shader and the pixel shader, so my suspicion is that it's some raster stage settings. But the raster stage shouldn't change the shape of the vertex shader output so drastically, should it?

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• libgdx ActorGestureListener.pan() parameters not moving actor in smooth line

  - by Roar Skullestad

  I override the pan method in ActorGestureListener to implement dragging actors in libgdx (scene2d). When I move individual pieces on a board they move smoothly, but when moving the whole board, the x and y coordinates that is sent to pan is "jumping", and in an increasingly amount the longer it is dragged. These are an example of the deltaY coordinates sent to pan when dragging smoothly downwards: 1.1156368 -0.13125038 -1.0500145 0.98439217 -1.0500202 0.91877174 -0.984396 0.9187679 -0.98439026 0.9187641 -0.13125038 This is how I move the camera: public void pan (InputEvent event, float x, float y, float deltaX, float deltaY) { cam.translate(-deltaX, -deltaY); I have been using both the delta values sent to pan and the real position values, but similar results. And since it is the coordinates that are wrong, it doesn't matter whether I move the board itself or the camera. What could the cause be for this and what is the solution? When I move camera only half the delta-values, it moves smoothly but only at half the speed of the mouse pointer: cam.translate(-deltaX / 2, -deltaY / 2); It seems like the moving of camera or board affects the mouse input coordinates. How can I drag at "mouse speed" and still get smooth movements? (This question was also posted on stackoverflow: http://stackoverflow.com/questions/20693020/libgdx-actorgesturelistener-pan-parameters-not-moving-actor-in-smooth-line)

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• How to store character moves (sprite animations)?

  - by Saad

  So I'm thinking about making a small rpg, mainly to test out different design patterns I've been learning about. But the one question that I'm not too sure on how to approach is how to store an array of character moves in the best way possible. So let's say I have arrays of different sprites. This is how I'm thinking about implementing it: array attack = new array (10); array attack2 = new array(5); (loop) //blit some image attack.push(imageInstance); (end loop) Now every time I want the animation I call on attack or attack2; is there a better structure? The problem with this is let's say there are 100 different attacks, and a player can have up to 10 attacks equipped. So how do I tell which attack the user has; should I use a hash map?

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• Making a surface transparent from blackness of texture

  - by Dan the Man

  I am making a "halo" shader in unity using GLSL. And I've come to a roadblock. What I need to do is take a texture, like the following, and make it transparent according to the darkness of it. And I don't want a cutout, because that cuts it off at a hard edge. This line of code doesn't seem to work. gl_FragColor = texture2D( vec4( _MainTex.r, _MainTex.g, _MainTex.b, _MainTex.a), vec2(textureCoordinates));

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