Intel's OpenSWR OpenGL Software Rasterizer Pulls In Tessellator From Microsoft Direct3D Code
Written by Michael Larabel in Intel on 11 December 2019 at 01:49 PM EST. 2 Comments
Intel's OpenSWR software rasterizer for OpenGL as an alternative to the likes of LLVMpipe could soon have OpenGL 4.0 and is a step closer to that code thanks to... Microsoft code.

OpenSWR is Intel's performance-minded software rasterizer for purposes like workstation visualizations and is where it outperforms the likes of LLVMpipe. This CPU-based OpenGL implementation can make use of not only AVX/AVX2 but also AVX-512 and other optimizations to support speedy CPU-based GL operations from laptops to Xeon Scalable hardware. Like LLVMpipe, OpenSWR does leverage LLVM in part. Those unfamiliar with this long-standing Intel open-source project can learn more at

OpenSWR for a long time has been at OpenGL 3.3 compliance but without much action towards GL 4.x, but it could soon be at least at OpenGL 4.0. SWR currently lacks ARB_gpu_shader5, ARB_sample_shading, and ARB_tessellation_shader, but that tessellation support could soon be knocked off. It's worth noting that LLVMpipe is also at GL 3.3 and tessellation support are among the few extensions it also has blocking GL 4.0 support.

Intel engineers in working towards ARB_tessellation_shader for OpenSWR have added a tessellator implementation. The origins of this tessellator are a bit ironic in that they pulled it from some of Microsoft's open-source Direct3D 11 code available via GitHub and under an MIT license.

ARB_tessellation_shader isn't flipped on yet for OpenSWR, but will hopefully be soon now that this Microsoft tessellator code has been merged and connected to the OpenSWR rasterizer.
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