Bug 2068

Summary: Depth buffer issues with transparent objects (Unichrome).
Product: Mesa Reporter: Thomas Hellström <thomas>
Component: Drivers/DRI/UnichromeAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED WONTFIX QA Contact:
Severity: normal    
Priority: high CC: xavier
Version: git   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:

Description Thomas Hellström 2004-12-12 14:18:53 UTC 
There seems to be depth buffer issues with transparent objects with the Unichrome. 
Although the objects are not visible against the background since they are
transparent, they seem to somehow obscure other objects. Perhaps objects that
get drawn later. 

To reproduce: 
Launch tucracer. At the beginning of the first lap, Tux will suddenly disappear,
and then reappear again.

Also at the start of the second level, The starting banner seems to be obscured
by a transparent object.
Comment 1 Felix Kühling 2004-12-12 18:39:27 UTC 
Sounds like the alpha test is broken. I vaguely remember fixing a related
problem in the Savage driver once. On the Savage there is a bit that says "write
Z after alpha test". If you don't set that bit then fragments that fail the
alpha test still write a Z value so that they "obscure" stuff that is drawn later.
Comment 2 Adam Jackson 2009-08-24 12:22:55 UTC 
Mass version move, cvs -> git
Comment 3 Ian Romanick 2015-11-30 23:44:40 UTC 
The Unichrome driver longer exists in Mesa.

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