[Mesa-dev] [PATCH 2/3] intel: Fix height in stencil buffer region allocation

[Chad Versace]

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On 07/11/2011 12:08 PM, Eric Anholt wrote:
> On Sat,  9 Jul 2011 09:01:07 -0700, Chad Versace <chad at chad-versace.us> wrote:
>> If the height of the stencil buffer were odd, then we allocated a region
>> whose height was too small --- `height / 2` rather than
>> `height / 2 + height % 2`.
> 
> Generally this is written "(height + 1) / 2" or "ALIGN(height, 2) / 2".

Ok. I'll change the patch to use the (height+1)/2 idiom.
 
> So, did the math end up working out so that Y tiling the W buffer was
> easier?

The math for decoding a W tile through a Y fence was slightly more complex than decoding an unfenced W tile. As far as arithmetic complexity is concerned, it doesn't matter which one we choose.

More importantly, I was absolutely unable to get the stencil buffer to work as non-tiled. I encountered bizarre behavior. However, if you really think that we should allocate the stencil buffer as non-tiled, then we can discuss on Wednesday possible interpretations of that bizarre behavior and the needed fixes.

- -- 
Chad Versace
chad at chad-versace.us
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