create your own sphere mesh simple 2D loop through 2 angles (spherical coordinate system 2 Cartesian). You can easily add ellipsoid properties (earth is not a sphere) if you want more precision. If not then you can use single sphere mesh for all planets and just scale it before use … let a be the … Read more
What is it about shaders that even potentially makes if statements performance problems? It has to do with how shaders get executed and where GPUs get their massive computing performance from. Separate shader invocations are usually executed in parallel, executing the same instructions at the same time. They’re simply executing them on different sets of … Read more
In a rendering, each mesh of the scene usually is transformed by the model matrix, the view matrix and the projection matrix. Finally the projected scene is mapped to the viewport. Model coordinates (Object coordinates) The model space is the local space, where within a mesh is defined. The vertex coordinates are defined in model … Read more
Outside of NVIDIA drivers, this does not work (reliably). Compliant drivers will only alias glVertexPointer (…) to attribute slot 0. NV in their infinite wisdom devised a standard non-standard scheme many years ago where they aliased all of the fixed-function pointers to certain attribute locations, but I do not know if new NV drivers support … Read more
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
File types that use separate indices for vertices and normals do not match to the OpenGL vertex model very directly. As you noticed, OpenGL uses a single set of indices. What you need to do is create an OpenGL vertex for each unique (vertex index, normal index) pair in your input. That takes a little … Read more
It all starts with glReadPixels, which you will use to transfer the pixels stored in a specific buffer on the GPU to the main memory (RAM). As you will notice in the documentation, there is no argument to choose which buffer. As is usual with OpenGL, the current buffer to read from is a state, … 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