<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 - Shadows are flickering in SuperTuxKart"
href="https://bugs.freedesktop.org/show_bug.cgi?id=110395">110395</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Shadows are flickering in SuperTuxKart
</td>
</tr>
<tr>
<th>Product</th>
<td>Mesa
</td>
</tr>
<tr>
<th>Version</th>
<td>git
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
<tr>
<th>OS</th>
<td>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>deveee@gmail.com
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
</tr></table>
<p>
<div>
<pre>In current git STK grass shadows are constantly flickering.
Here is original bug report:
<a href="https://github.com/supertuxkart/stk-code/issues/3824">https://github.com/supertuxkart/stk-code/issues/3824</a>
Basically it is related to the file:
<a href="https://github.com/supertuxkart/stk-code/blob/master/data/shaders/sp_grass_shadow.vert">https://github.com/supertuxkart/stk-code/blob/master/data/shaders/sp_grass_shadow.vert</a>
I can "fix" this by changing order of the "layer" and "wind_direction" uniform
variables. Maybe it's just a case.
And it can be reproduced on any track with grass/trees when shadows are enabled
in options, eg. in Nessie's Pond.
Not sure which graphics cards are affected. Maybe <= gen8, because original bug
report is from haswell and I was testing it on ivybridge.
Git bisect shows:
eca4a6548d07bbbb02a7768edb397bad7b72cfc2 is the first bad commit
commit eca4a6548d07bbbb02a7768edb397bad7b72cfc2
Author: Danylo Piliaiev <<a href="mailto:danylo.piliaiev@gmail.com">danylo.piliaiev@gmail.com</a>>
Date: Mon Jul 2 17:04:23 2018 +0300
i965: Disable dual source blending when shader doesn't support it on gen8+
Dual source blending behaviour is undefined when shader doesn't
have second color output, dismissing fragment in such situation
leads to a hang on gen8+ if depth test in enabled.
Since blending cannot be gracefully fixed in such case and the result
is undefined - blending is simply disabled.
v2 (Kenneth Graunke):
- Listen to BRW_NEW_FS_PROG_DATA in 3DSTATE_PS_BLEND
- Also whack BLEND_STATE[] to keep the two in sync, since we're not
sure exactly which copy of the redundant info the hardware will use.
Bugzilla: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [GEN8+] Hang when discarding a fragment if dual source blending is enabled but shader doesn't support it"
href="show_bug.cgi?id=107088">https://bugs.freedesktop.org/show_bug.cgi?id=107088</a>
Signed-off-by: Danylo Piliaiev <<a href="mailto:danylo.piliaiev@globallogic.com">danylo.piliaiev@globallogic.com</a>>
Reviewed-by: Jason Ekstrand <<a href="mailto:jason@jlekstrand.net">jason@jlekstrand.net</a>>
Reviewed-by: Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>>
:040000 040000 e4887675a8acfdd017f7022f553a8bfeefc2b31b
8eb8649a23e09c70cb3088873249763e05f5452e M src</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the assignee for the bug.</li>
<li>You are the QA Contact for the bug.</li>
</ul>
</body>
</html>