Bug 13835 - glDrawBuffers implemented incorrect when draw to GL_BACK_LEFT
Summary: glDrawBuffers implemented incorrect when draw to GL_BACK_LEFT
Status: VERIFIED FIXED
Alias: None
Product: Mesa
Classification: Unclassified
Component: Mesa core (show other bugs)
Version: git
Hardware: x86 (IA32) Linux (All)
: medium normal
Assignee: Eric Anholt
QA Contact:
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Reported: 2007-12-27 22:56 UTC by WuNian
Modified: 2009-08-24 12:28 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:

Attachments
test case (3.49 KB, text/plain)
2007-12-27 22:59 UTC, WuNian 		Details
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Description WuNian 2007-12-27 22:56:32 UTC 
On i965 platform, when call glDrawBuffers to draw GL_FRONT_LEFT and GL_BACK_LEFT, then read back the pixels, pixels in GL_FRONT_LEFT buffer is as expected, but pixels in GL_BACK_LEFT buffer is incorrect.

On i915 platform, the bug does not exist. i965 driver has not implemented the glDrawBuffers feature(multi render target), so I think this is mesa xlib's bug.
Comment 1 WuNian 2007-12-27 22:59:52 UTC 
Created attachment 13391 [details]
test case

On i965 platform, I got below result:

draw buffers number: 2
error! i is: 1
expected: 0.800000 0.300000 0.700000 1.000000
actual: 0.800000 0.501961 0.200000 1.000000
Comment 2 Michael Fu 2008-01-01 23:26:01 UTC 
software rendering bug.
Comment 3 Brian Paul 2008-01-06 09:46:27 UTC 
Fixed in core Mesa.  Haven't test i965.

The problem was glDrawBuffers(2, [GL_FRONT_LEFT, GL_BACK_LEFT]) wasn't being interpreted correctly.  The fragment color was only getting written to the first buffer.
Comment 4 WuNian 2008-01-08 14:05:28 UTC 
Verified on i965 platform.
Comment 5 Adam Jackson 2009-08-24 12:28:58 UTC 
Mass version move, cvs -> git

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