Construct 4×4 transform matrix instead of Quaternions. Do not forget that OpenGL has column wise matrix so for double m[16]; is X axis vector in m[ 0],m[ 1],m[ 2] is Y axis vector in m[ 4],m[ 5],m[ 6] is Z axis vector in m[ 8],m[ 9],m[10] and position is in m[12],m[13],m[14] The LCS mean local … Read more
Background map Ok I created a test RGBA map as 2 images one containing RGB (on the left) and second with the alpha channel (on the right) so you can see them both. Of coarse they are combined to form single RGBA texture. I blurred them both a bit to obtain better visual effects on … Read more
glVertexAttribPointer has two flaws, one of them semi-subjective, the other objective. The first flaw is its dependency on GL_ARRAY_BUFFER. This means that the behavior of glVertexAttribPointer is contingent on whatever was bound to GL_ARRAY_BUFFER at the time it was called. But once it is called, what is bound to GL_ARRAY_BUFFER no longer matters; the buffer … Read more
This question is almost impossible to answer because OpenGL by itself is just a front end API, and as long as an implementations adheres to the specification and the outcome conforms to this it can be done any way you like. The question may have been: How does an OpenGL driver work on the lowest … Read more
glReadPixels runnable PBO example The example below generates either: one ppm per frame at 200 FPS and no extra dependencies, one png per frame at 600 FPS with libpng one mpg for all frames at 1200 FPS with FFmpeg on a ramfs. The better the compression, the larger the FPS, so we must be memory … Read more
It flows from the definition of a normal. Suppose you have the normal, N, and a vector, V, a tangent vector at the same position on the object as the normal. Then by definition N·V = 0. Tangent vectors run in the same direction as the surface of an object. So if your surface is … Read more
For starters I would use 4D -> 3D projection instead of cut by hyperplane. The result is not the same but will get you closer to your goal (so you can latter upgrade this to cut). So similarly like in 3D -> 2D conversions used in graphics you got 2 choices one is using perspective … Read more
For ray picking rendered objects (like by mouse) the best option is to use the already rendered buffers as there is very little cost of reading them in comparison to ray intersection tests on complex scene. The idea is to render each pick-able rendered object to separate buffer per each info you need about them … Read more
but I still don’t know whether or not the gl_FragCoord.z is linear. Whether gl_FragCoord.z is linear or not depends on, the projection matrix. While for Orthographic Projection gl_FragCoord.z is linear, for Perspective Projection it is not linear. In general, the depth (gl_FragCoord.z and gl_FragDepth) is calculated as follows (see GLSL gl_FragCoord.z Calculation and Setting gl_FragDepth): … Read more
Texture coordinates specify the point in the texture image that will correspond to the vertex you are specifying them for. Think of a rectangular rubber sheet with your texture image printed on it, where the length of each side is normalized to the range 0-1. Now let’s say you wanted to draw a triangle using … Read more