> I noticed with Crysis that really distant objects "sparkle" like there's a 
> coincident surface glitch. I suspect that what's really happening is 
> limited Z-buffer precision.

Exactly.  Even with 24bit precision, when that's spread over viewing 
distances between 10cm and 10km you still get problems with far away objects 
being drawn correctly.

> The glitch I'm tolding about happens on a custom level at distances of 
> only a few feet, so I suspect the level author set some flag wrong or 
> seomthing.

More likely he just put two surfaces on the same plane somehow (with 
different textures).  Of course if the points are in exactly the same place, 
it's just going to be down to floating point precision and rounding errors 
as to which one gets drawn in front for each pixel.  Usually if you really 
do want two surfaces at the same point (eg a poster on a wall) you apply a 
"z buffer bias" to ensure one always gets drawn on top of the other even 
though the geometry is in the same place and even when the z buffer 
precision is low (eg far away).

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