Reply To: Some errors at startup

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Oliver Kreylos

SWR is neat, but the 29x – 52x speed-up can not be expected for this application. The primary difference between SWR and vanilla Mesa is multi-threading in the vertex processing stage, meaning that SWR can use multiple CPU cores for geometry-heavy workloads like the isosurface/slice rendering for large 3D data sets they are targeting, i.e., tens of millions of triangles per frame. The 29x speed-up for 3M triangle geometries is achieved on a machine with 36 CPU cores.

Furthermore, the AR Sandbox is fill-limited, not geometry-limited. The rendered surface consists of exactly 612,162 triangles ( (640-1)*(480-1)*2 ), and the majority of work is per-pixel work in the fragment shader. The water simulation is even more extreme; it only renders 2 (two) triangles per computation step, and everything is done in fragment shaders.

The fragment processing stage of SWR is not architecturally different from vanilla Mesa, which is already multi-threaded.

SWR is meant for one specific application: visualization of tera-scale 3D data on massively parallel supercomputers, using fixed-function OpenGL as employed by Vtk/ParaView/VisIt. It probably won’t help much on a typical gaming PC or laptop with 2-4 CPU cores, and with fill-limited software using complex shaders.

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