<html>
<head>
<base href="https://bugs.freedesktop.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [IVB] LINE_STRIPs following a TRIANGLE_FAN fail to use primitive restart"
href="https://bugs.freedesktop.org/show_bug.cgi?id=109451">109451</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[IVB] LINE_STRIPs following a TRIANGLE_FAN fail to use primitive restart
</td>
</tr>
<tr>
<th>Product</th>
<td>Mesa
</td>
</tr>
<tr>
<th>Version</th>
<td>18.3
</td>
</tr>
<tr>
<th>Hardware</th>
<td>x86-64 (AMD64)
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux (All)
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Component</th>
<td>Drivers/DRI/i965
</td>
</tr>
<tr>
<th>Assignee</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>perso@elementw.net
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=143227" name="attach_143227" title="apitrace of example program">attachment 143227</a> <a href="attachment.cgi?id=143227&action=edit" title="apitrace of example program">[details]</a></span>
apitrace of example program
Originally reported as a Blender bug: <a href="https://developer.blender.org/T60762">https://developer.blender.org/T60762</a>
(which it is not)
Using desktop GL 3.3+.
Steps to reproduce:
* prepare a vertex and index buffer
* enable GL_PRIMITIVE_RESTART
* draw a GL_TRIANGLE_FAN using those buffers
* draw any number of GL_LINE_STRIPs with those same buffers
Drawing a GL_TRIANGLE_FAN prior to GL_LINE_STRIPs makes the strip draw calls
fail to use restart markers (here, 0xFF), resulting in the line strips'
supposedly unconnected strips being connected through a point of invalid
coordinates (observed to consistently be (0, 0, 0)).
IOW, restart markers seems to be (re-)considered as normal indices.
Interfering with GL calls that read or write to the index buffer makes the
problem go away, hinting at a GL state tracking or cache issue.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the QA Contact for the bug.</li>
<li>You are the assignee for the bug.</li>
</ul>
</body>
</html>