As I understand it, Blender uses OpenGL for viewport drawing and preview rendering, but not for full rendering. For a final render, it uses either OpenCL or CUDA (depending on your graphics card). A few of the steps in the OpenGL pipeline are fragment shading, tessellation, and rasterization. From what I know about Blender Internal, it is a hybrid engine that uses both rasterization and ray-tracing. It also does shading and tessellation. Considering that these steps are also done in OpenGL, it seems to me that BI uses some steps of the OpenGL process for full rendering.

So that is my question: does Blender Internal use some of the OpenGL steps (fragment shading, tessellation, and rasterization), or does it recalculate those steps specifically for full rendering? I read a while back that BI doesn't use any OpenGL, but I'm not sure if that person was correct, or if I simply misunderstood what he wrote.

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    $\begingroup$ With Blender Internal all the work is done with CPU and has all the system RAM available. OpenGL uses and is accelerated with GPU. $\endgroup$ Apr 14, 2018 at 19:33
  • $\begingroup$ Yes, I’m aware that BI uses the CPU and that OpenGL uses the GPU. So based on that, Blender Internal has nothing to do with OpenGL because it uses different hardware than what OpenGL uses. This would also mean that Blender Internal does its own rasterization and tessellation, which is completely different than the rasterization and tessellation that OpenGL does. Am I right? $\endgroup$
    – MeshHead
    Apr 14, 2018 at 23:01
  • $\begingroup$ It's not completely different. It's the same process, but different implementation. $\endgroup$ Apr 15, 2018 at 9:14


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