# Does Storm support OSD CPU tessellation?

**URL:** <https://forum.aousd.org/t/does-storm-support-osd-cpu-tessellation/909>\
**Category:** Hydra\
**Tags:** rendering\
**Created:** [November 10, 2023, 9:38am UTC](https://forum.aousd.org/t/does-storm-support-osd-cpu-tessellation/909 "2023-11-10T09:38:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![wangfr](https://avatars.discourse-cdn.com/v4/letter/w/3be4f8/32.png) [@wangfr](https://forum.aousd.org/u/wangfr)\
**Post date:** [November 10, 2023, 9:38am UTC](https://forum.aousd.org/t/does-storm-support-osd-cpu-tessellation/909/1 "2023-11-10T09:38:00Z")

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Hi everyone,

As I know, current OpenSubdiv refinement seems to do tessellation computation in GPU through specific tessellation related stages. For a few backend (e.g. WebGPU) there is not tessellation supported, is that possible to use OSD CPU tessellation? But it seems I cannot find where to enable it. Or it is not supported yet in Hydra Storm.

Thanks,  
Francis

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**Author:** ![tomc](https://avatars.discourse-cdn.com/v4/letter/t/8dc957/32.png) [@tomc](https://forum.aousd.org/u/tomc)\
**Post date:** [November 18, 2023, 12:01am UTC](https://forum.aousd.org/t/does-storm-support-osd-cpu-tessellation/909/2 "2023-11-18T00:01:34Z")

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Hi Francis,

OSD supports CPU tessellation, and it looks like our Hydra Storm subdivision computation class does support CPU refinement: [https://github.com/PixarAnimationStudios/OpenUSD/blob/release/pxr/imaging/hdSt/subdivision.h](https://github.com/PixarAnimationStudios/OpenUSD/blob/release/pxr/imaging/hdSt/subdivision.h) … However, hdSt/mesh.cpp is currently only calling GPU versions of the computation.

For uniform refinement I thought we only use compute shaders, not tessellation shaders? We have an adaptive refinement mode that definitely does rely on tessellation shaders, and would likely need to be disabled, but that’s currently an opt-in at the asset level anyway.

Hope this helps!  
Tom