[Bug 96354] [i965] GS instancing (gl_InvocationID) reads garbage instead of what the vertex shader says
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Fri Jun 3 04:28:34 UTC 2016
https://bugs.freedesktop.org/show_bug.cgi?id=96354
Bug ID: 96354
Summary: [i965] GS instancing (gl_InvocationID) reads garbage
instead of what the vertex shader says
Product: Mesa
Version: git
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: NEW
Severity: normal
Priority: medium
Component: Drivers/DRI/i965
Assignee: idr at freedesktop.org
Reporter: thematrixeatsyou at gmail.com
QA Contact: intel-3d-bugs at lists.freedesktop.org
Created attachment 124298
--> https://bugs.freedesktop.org/attachment.cgi?id=124298&action=edit
Point-to-cube geometry shader with toggleable GS instancing
Overview:
If GLSL 4.00 GS instancing is enabled via the `layout(invocations = x) in;`
layout specifier (where x > 1), the GS no longer reads valid data from the
vertex shader.
Steps to Reproduce:
You will need a GPU which currently supports GLSL 4.00. This is currently
restricted to gen8+.
1) Find a geometry shader you can change.
2) Ensure the #version directive is 400 or higher - if not, bump it up to
400.
3) Add this line near the top of it:
layout(invocations = 2) in;
4) Observe that the geometry is now garbage or apparently missing (degenerate
/ culled primitives).
Attached is a geometry shader with toggleable GS instancing. It requires
GL_POINTS as input.
vec3 v_vtx[], v_col[] are vertex and colour attribute data respectively.
mat4 Mproj, Mcam are projection and modelview matrices respectively.
vec3 campos is the position of the camera in the world.
Expected Results:
For the given shader, input points should be expanded to cubes of their
respective colours.
Actual Results:
A single black cube appears at (0, 0, 0).
In some frames you may see intermittent garbage - this is noticeable at
~3000FPS with vsync disabled.
The uniform data is being read correctly, but the VS input data is completely
wrong.
Additional Information:
Build Date: 2016-06-03 ~15:30 +1200
Git Revision: d10ae20b9678f1a5b8a81716c68e612662665277
GPU: Intel HD 530 (Skylake GT2)
OS: Void Linux
This bug may be relevant (#93859) - the output is SIMD8:
https://bugs.freedesktop.org/show_bug.cgi?id=93859
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