When rendering point sprites, the value delivered to the gl_PointCoord special variable in the fragment shader is wrong; probably uninitialized data. Attached there is a small program that triggers the problem, and an screenshot taken on a Intel® GM45 (incorrect rendering) and another taken on a Radeon R700 (correct rendering), both under Mesa. Compile the program with: $ cc -o ball ball.c -lglut -lGLEW -lm
Created attachment 59958 [details] Program that triggers the problem.
Created attachment 59959 [details] Intel rendering (just a black screen).
Created attachment 59960 [details] Radeon rendering (correct, a bluish ball)
Bug #43580 is probably related.
New info, the problem seems to be restricted to some devices. The problem is present on the following renderer/software: OpenGL vendor string: Tungsten Graphics, Inc OpenGL renderer string: Mesa DRI Mobile Intel® GM45 Express Chipset x86/MMX/SSE2 OpenGL version string: 2.1 Mesa 8.1-devel (git-897af1d oneiric-oibaf-ppa) OpenGL shading language version string: 1.20 While in the following renderer/software, the sample program renders fine: OpenGL vendor string: Tungsten Graphics, Inc OpenGL renderer string: Mesa DRI Intel(R) Sandybridge Mobile OpenGL version string: 2.1 Mesa 7.11 OpenGL shading language version string: 1.20
commit 43af02ac731dac7d80f7e47feb0c80e4da156769 Author: Yuanhan Liu <yuanhan.liu@linux.intel.com> Date: Mon Feb 27 15:46:32 2012 +0800 i965: handle gl_PointCoord for Gen4 and Gen5 platforms
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