Bug 13835

Summary:	glDrawBuffers implemented incorrect when draw to GL_BACK_LEFT
Product:	Mesa	Reporter:	WuNian <nian.wu>
Component:	Mesa core	Assignee:	Eric Anholt <eric>
Status:	VERIFIED FIXED	QA Contact:
Severity:	normal
Priority:	medium	CC:	eric
Version:	git
Hardware:	x86 (IA32)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:
Attachments:	test case

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

Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.