Re: Multi-pass rendering

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Orad Hi-Tec Systems (orad_u++at++netvision.net.il)
Tue, 11 Mar 1997 18:14:33 +0200

Javier Castellar wrote:
>
> The only parallel texture paging will happen if you request texture paging
> right after a fill limited operation. Then in this case you will obtain free
> GEs time while the RMs are draining the internal buffers.
>
> 1) fill limited operation
> 2) texture paging
>
> -Javier

This is not a sufficient condition.
The GE may run parallel to the RMs, but, the texture memory
update inside the RMs will "fight" with texture memory access
by normal textured rasterization. In other words, the texture
memory is NOT dual-port. Parallelism at this stage depends on
the texture memory read access bandwidth. Thisd epends on
many things: the pixel area of textured polygons (vs. un-textured
polygons), the type of texture
filters used, the bits-per-texel in the textures.
 (trilinear mipmap, for example, requires 8 texels
for each rasterized pixel). Moreover, I guess it also depends
on the locality of subsequent texture memory read accesses --
a high-res texture rasterized into a small polygon (with
non-mipmap filter), will increase the bandwidth.

It sums up to: pretty unpredictable.

Moshe Nissim
Orad Hi-Tec Systems
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