Bug 54652 - [i915] Incorrect GLSL texture mapping (TEX/TEXLD vs TXP/TEXLDP)
Summary: [i915] Incorrect GLSL texture mapping (TEX/TEXLD vs TXP/TEXLDP)
Alias: None
Product: Mesa
Classification: Unclassified
Component: Drivers/DRI/i915 (show other bugs)
Version: git
Hardware: x86 (IA32) Linux (All)
: medium normal
Assignee: Ian Romanick
QA Contact:
Depends on:
Reported: 2012-09-07 19:55 UTC by Krzysztof Kotlenga
Modified: 2019-09-18 19:35 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

Incorrect rendering example (61.30 KB, image/png)
2012-09-07 19:55 UTC, Krzysztof Kotlenga

Description Krzysztof Kotlenga 2012-09-07 19:55:45 UTC
Created attachment 66810 [details]
Incorrect rendering example

The problem is that perspective correct mapping is not being done at all. I've tried to do some basic analysis to help as much as I could, so:

Quick facts:
- the problem doesn't happen with i915g
- it doesn't happen with the 'reflect' mesa demo (no GLSL -> correct rendering)
- affects mesa as old as 7.11 from Fedora 16 and as new as mesa 9.0-devel (git-a96119c) (8.0.4 too, haven't checked other versions)

I think (hope) that the interesting thing to note here is that - as I've seen with INTEL_DEBUG=wm - the 'reflect' demo results in TEXLDP instruction being used, while any WebGL (effectively GLSL) demos only show TEXLD.

I know that throwing WebGL implementation at the i915 might not be the best test case, but I couldn't get any native GLSL demo running. WebGL demos mostly work fine though and are easy to run:


The shaders are also extremely simple. The attached screenshot shows the demo from the second link with a different texture. Chromium/Mozilla - doesn't matter.

Also (mis)reported elsewhere:
"WebGL w. MESA driver results in affine texture mapping"
Comment 1 Elizabeth 2017-10-27 20:32:19 UTC
Hello Krzysztof, is this still valid with latest SW? Otherwise closing soon. Thank you.
Comment 2 Krzysztof Kotlenga 2017-10-31 13:13:29 UTC
(In reply to Elizabeth from comment #1)
> Hello Krzysztof, is this still valid with latest SW? Otherwise closing soon.
> Thank you.

Hi, please postpone closing this at least for a few weeks. I'm putting this on my TODO, which is way too long right now. Nevertheless, I'm happy to provide feedback.
Comment 3 GitLab Migration User 2019-09-18 19:35:16 UTC
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/mesa/mesa/issues/717.

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