Re: Z-buffer problem

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Allan Schaffer (aschaffe)
Thu, 6 Oct 1994 14:00:37 -0700

On Oct 6, 1:46pm, Ran Yakir wrote:
>
> When working with multisampling (as in an ONYX with RE2), the Z
> buffer is not used to keep Z values. Instead, a Z value is attached
> to each subsample (or, you might say, the Z buffer is multisampled).
> That explains why you could not read valid values out of the Z
> buffer.
>
> Maybe it is a good opportunity to ask SGI people for a documented way
> of getting multisampled Z buffer values.

This is correct; each subsample has its own screen-space Z value (for
the details on that, see the "RealityEngine graphics" paper in the
'93 SIGGRAPH proceedings).

Unfortunately there is no way to read back multisampled Z values.
In order to read back the Z buffer you'll have to forsake
multisampling.

Alla

-- 
Allan Schaffer
Silicon Graphics
aschaffe++at++sgi.com

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