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<body><span class="vcard"><a class="email" href="mailto:jfonseca@vmware.com" title="José Fonseca <jfonseca@vmware.com>"> <span class="fn">José Fonseca</span></a>
</span> changed
<a class="bz_bug_link
bz_status_NEW "
title="NEW - [llvmpipe] Front/Backfaces do not get the same depth values when interpolated"
href="https://bugs.freedesktop.org/show_bug.cgi?id=78914">bug 78914</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Summary</td>
<td>[llvmpipe] Front/Backfaces do not cover the same pixels when rasterized
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<td>[llvmpipe] Front/Backfaces do not get the same depth values when interpolated
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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [llvmpipe] Front/Backfaces do not get the same depth values when interpolated"
href="https://bugs.freedesktop.org/show_bug.cgi?id=78914#c20">Comment # 20</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [llvmpipe] Front/Backfaces do not get the same depth values when interpolated"
href="https://bugs.freedesktop.org/show_bug.cgi?id=78914">bug 78914</a>
from <span class="vcard"><a class="email" href="mailto:jfonseca@vmware.com" title="José Fonseca <jfonseca@vmware.com>"> <span class="fn">José Fonseca</span></a>
</span></b>
<pre><span class="quote">> 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).</span >
I agree. It might be possible to do better (barycentric interpolation might
help), but it is complicated to ensure we get exactly the same depth values in
all circumstances, particularly because llvmpipe wants to strike a good balance
of performance/accuracy.
OpenGL application developers should make use of glPolygonOffset to prevent
depth-fighting in a portable way.</pre>
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