[Mesa-dev] DEFAULT_SOFTWARE_DEPTH_BITS=31

[burlen]

On 11/07/2013 06:42 AM, Brian Paul wrote:
> On 11/06/2013 04:59 PM, burlen wrote:
>> On 11/06/2013 12:58 PM, Brian Paul wrote:
>>> On 11/06/2013 12:34 PM, burlen wrote:
>>>> When I build osmesa with --with-osmesa-bits=32 I notice that I get 31
>>>> bits by way of the compile line define 
>>>> -DDEFAULT_SOFTWARE_DEPTH_BITS=31.
>>>> What's the story with the number 31? Is 31 bits really better than 32?
>>>
>>> IIRC, 32 bit Z never worked properly because of float->int conversion
>>> problems and such.  I think I found that 31 bits worked though.  It's
>>> been a long time...
>>>
>>
>> I'm using OSMesa with VTK for rendering on systems that do not have
>> graphics hardware. I need higher than default depth buffer with OSMesa
>> to prevent z-buffer fighting artifacts in some cases when rendering in
>> parallel. I found that --with-osmesa-bits=32 does the trick. however
>> when building osmesa with 32 bits, most line rendering fails. Here is a
>> representative image diff from our regression suite that shows an
>> example of the bug
>> http://open.cdash.org/testDetails.php?test=216532438&build=3087854
>> <https://urldefense.proofpoint.com/v1/url?u=http://open.cdash.org/testDetails.php?test%3D216532438%26build%3D3087854&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=lGQMzzTgII0I7jefp2FHq7WtZ%2BTLs8wadB%2BiIj9xpBY%3D%0A&m=RSWC%2F0O7rDfFjJWLpUVeoSImwj8RMeWUaKnhSM%2Fx2Nk%3D%0A&s=11a634d8629f9a7fc613440fd0337a158f6951974892d2427bae4b5f570ad641> 
>>
>> , there are 80 other failed tests, the ones I examined were all the 
>> same.
>>
>> Experimenting with --with-osmesa-bits options, I've found that using 32
>> causes the issue, while using 8 , 16 or not using it all doesn't. Do you
>> have any idea about this?
>
> I set DEFAULT_SOFTWARE_DEPTH_BITS=32 and tried a few demo programs and 
> they look OK so far.
>
> Could you possibly create an apitrace of one of the failing cases?
>
did you set DEFAULT_SOFTWARE_DEPTH_BITS=32 or --with-osmesa-bits=32? 
--with-osmesa-bits=16 also sets depth bits to 31, and that case doesn't 
have the problem. so seems that it's something other than the depth bits 
about the --with-osmesa-bits=32 build.

I'll see about the apitrace

Thanks
Burlen