Some wonky rendering occurs with Mesa 13.0.2 (not bisected, so unsure where this issue has started) when using Intel HW OpenGL. The problem does not occur with full software rendering (llvm softpipe) e.g. running with LIBGL_ALWAYS_SOFTWARE=1
As I am not sure what the exact issue is (might be incorrect clipping or vector calculation etc.) the best thing is to demonstrate, two screenshots and a OGV format video available at: http://tnsp.org/~ccr/intel-gfx/blender/
In the video pay attention to the "floor grid" lines, which go about weirdly. The other minor glitches are artifacts of the screen capture and not actually visible.
I'll try latest GIT and bisecting during next weekend as I'll have more time then.
-- Linux distribution: Debian GNU/Linux testing (stretch)
-- System architecture: amd64
Foreign architectures: i386
-- Machine: Asus H97M-PLUS, Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz
-- Kernel version: 4.8.15-grsec
-- Chipset: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller (rev 06)
-- Display connector(s): HDMI (2560x1440)
-- Window manager: WindowMaker 0.95.7-6+b1
-- xf86-video-intel: GIT
-- X server: Xorg 2:1.19.0-3
-- Mesa: 13.0.2-3
-- libpixman: 0.34.0-1
-- libdrm version: 2.4.74-1
Was bored, so I did the bisecting already. The culprit seems to be this commit in Mesa GIT: 88d28aa4d9edec33ef7bcf1f56b77fbb756a24f8 "i965: Stop XY clipping point and line primitives."
Thanks for the bisect! I can confirm the bug on Haswell. As another data point, Skylake seems to be working OK...
This patch seems to fix it:
Tested the patch (without any changes suggested by Chris, tho), and it is working on my Haswell.
Should be fixed by:
Author: Kenneth Graunke <firstname.lastname@example.org>
Date: Wed Jan 11 21:38:52 2017 -0800
i965: Always scissor on Gen6-7.5 instead of disabling guardband.
Previously we disabled the guardband when the viewport was smaller than
the framebuffer on Gen6-7.5, to prevent portions of primitives from
being draw outside of the viewport. On Gen8+, we relied on the viewport
extents test to effectively scissor this away for us.
We can simply always enable scissoring instead. We already include the
viewport in the scissor rectangle, so this will effectively do the
viewport extents test for us. (The only difference is that the scissor
rectangle doesn't support sub-pixel values. I think that's okay.)
Given that the viewport extents test is essentially a second scissor,
and is enabled for basically all 3D drawing on Gen8+, it stands to
reason that scissoring is cheap. Enabling the guardband reduces the
cost of clipping, which is expensive.
The Windows driver appears to never disable guardband clipping, and
appears to use scissoring in this case. I don't know if they leave
it on universally though.
This fixes misrendering in Blender, where the "floor plane" grid lines
started rendering at wrong angles after I disabled XY clipping of line
primitives. Enabling the guardband seems to solve the issue.
Cc: "17.0" <email@example.com>
Signed-off-by: Kenneth Graunke <firstname.lastname@example.org>
Reviewed-by: Jason Ekstrand <email@example.com>
or at least the series including that. This will be in Mesa 17.0.
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