[Mesa-dev] [Bug 105464] Reading per-patch outputs in Tessellation Control Shader returns undefined values

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105464

--- Comment #1 from Philip Rebohle <philip.rebohle at tu-dortmund.de> ---
Created attachment 138038
  --> https://bugs.freedesktop.org/attachment.cgi?id=138038&action=edit
Witcher 3 hull shader which may suffer from the same issue

FWIW, the tessellation demo works correctly with AMDVLK with the patched
shader. On RADV, the tessellation levels are seemingly random, and its
behaviour changes by just changing the location number.

A similar issue occurs in The Witcher 3 when run with DXVK, where water
surfaces have incorrect tessellation factors applied on RADV. It reportedly
renders correctly on Nvidia.

In this case however, there is only one single invocation writing per-patch
outputs. A workaround that makes this particular shader work correctly on RADV
is to write all per-patch outputs to an array with storage class Private first,
reading the tessellation factors from that array, and finally copying the
contents of the temporary array to the output array, which tells me that
reading from the output array again returns incorrect results.

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