[Mesa-dev] [PATCH 2/2] u_blitter: Add an option to draw the triangles using an index buffer.

[Eric Anholt]

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
rasterization.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 832 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/mesa-dev/attachments/20180712/f027696a/attachment.sig>