[Mesa-dev] [PATCH 2/2] u_blitter: Add an option to draw the triangles using an index buffer.
eric at anholt.net
Thu Jul 12 18:48:53 UTC 2018
Roland Scheidegger <sroland at vmware.com> writes:
> Am 12.07.2018 um 00:05 schrieb Eric Anholt:
>> For V3D, the HW will interpolate slightly differently along the shared
>> edge of the trifan. The conformance tests manage to catch this in the
>> nearest_consistency_* group. To get interpolation to match, we need the
>> last vertex of the triangle to be shared.
>> I first tried implementing draw_rectangle to do triangles instead, but
>> that was quite a bit (147 lines) of code duplication from u_blitter, and
>> this seems much simpler and less likely to break as u_blitter changes.
> I'm curious, how does interpolation work on that hw?
> Does it use the provoking vertex as some sort of reference? If so would
> it actually work if you switched to provoking vertex first (if you can)?
> (But I'm really just curious, the patch looks alright to me.)
As far as I know, provoking vertex is just about where flat shading
comes from. I tried forcing it on/off, and got no change in
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