[Mesa-dev] [Bug 78914] [llvmpipe] Front/Backfaces do not cover the same pixels when rasterized

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=78914

--- Comment #19 from Roland Scheidegger <sroland at vmware.com> ---
depth test as such is as accurate as it could be. Doing interpolation with as
much precision as possible is not all that easy due to properties of floating
point arithmetic. In particular for the math the order of vertices matter.
Reordering would be possible, though still does not guarantee the same results
for fragments along a shared edge (unless the tri shares all vertices, that is
it's really the same tri with reordered edges).
But I agree doing better would be nice, I'm just not entirely sure what clever
tricks need to be done to achieve this.
There's also a slight bug in the implementation I believe, the interpolation
should be done with snapped (fixed point) coordinates, however we do the
interpolation setup with float coordinates. I'm not sure though this would help
here, but at least in contrast to other interpolation issues this one wouldn't
be all that difficult to fix. Another issue is that if you have some attributes
with large gradients on a somewhat small triangle, you can get huge errors the
further the triangle is away from the framebuffer origin. So, interpolation is
definitely not perfect.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20140527/b459e60f/attachment.html>