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      <base href="https://bugs.freedesktop.org/" />
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        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - [nva5] Wrong provoking vertex is selected for flat attribute interpolation (clipping?)"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=66642">66642</a>
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>nouveau@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[nva5] Wrong provoking vertex is selected for flat attribute interpolation (clipping?)
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux (All)
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>alzeih@gmail.com
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>x86-64 (AMD64)
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>git
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Drivers/DRI/nouveau
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>Mesa
          </td>
        </tr></table>
      <p>
        <div>
        <pre>The following piglit test:

  interpolation-flat-gl_BackColor-smooth-none.shader_test

appears to select the wrong provoking vertex depending on the exact value of
v[0].y.

For v[0].y > -1.0, the triangle ends up red.
For v[0].y = -1.0, the triangle ends up green.
For v[0].y < -1.0, the triangle ends up (correctly) blue.

Hardware: nva5 (GT330M) in MacBookPro6,2
Mesa version: 1415a1884c
Kernel: 3.9.8-1-ARCH

Suspect the clipper doesn't respect the index of the provoking vertex in the
triangle?</pre>
        </div>
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