Bug 11656

Summary: Vertex point is rendered differently at different postion
Product: Mesa Reporter: Shuang He <shuang.he>
Component: Drivers/DRI/i965Assignee: Zou Nan hai <nanhai.zou>
Status: VERIFIED FIXED QA Contact:
Severity: normal    
Priority: medium CC: bugzi11.fdo.tormod, dri-devel, nian.wu, wei.z.wang
Version: git   
Hardware: Other   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments: test case

Description Shuang He 2007-07-18 23:01:10 UTC
with or without point anti-alias enabled, point size of 2.6, a vertex point drawn at different position will have different shape. And also, the anti-alias doesn't seem to function.
Comment 1 Shuang He 2007-07-18 23:10:00 UTC
Created attachment 10801 [details]
test case

point anti-alias is enabled , and point size is set to 2.6
draw a vertex point at the center of the window
clear the window and draw a new vertex point have a small offset to the center.
the RGB value of pixels drawn will be display
Comment 2 Tormod Volden 2007-07-19 14:32:27 UTC
The geometries are different because the vertex is shifted by a sub-pixel length. As long as sub-pixel rendering is not used:

             XXX
offset 0.0:  XXX    Vertex centre is on a pixel:
             XXX    2n+1 pixels must be used to keep symmetry

              XX
offset 0.5:  XXXX   Vertex centre is between two pixels:
              XX    2n pixels must be used to keep symmetry

              XXX
offset 1.0:   XXX   (Vertex centre is again on a pixel)
              XXX

BTW, using fglrx (ATI X1300) I get a red dot, using ati (ATI X700) I get a dark yellow dot...
Comment 3 Zou Nan hai 2008-03-17 02:03:41 UTC
Fixed in mesa.
Comment 4 Shuang He 2008-03-17 18:54:37 UTC
verified, thanks
Comment 5 Adam Jackson 2009-08-24 12:27:23 UTC
Mass version move, cvs -> git

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