On Wednesday 09 February 2005 23:59, Daniel Phillips wrote: > Hi Timothy, > > I think I've got enough of a handle on the design to attempt a budget > for the dedicated multipliers. Assumptions: > > - Four clocks to set up each span > > - Interpolate 16 parameters (don't interpolate Z, yes I know it's > currently planned otherwise) > > - Assume fog and LOD need 16 bit precision (they might not) > > - Assume color is perspective-correct (some think it's ok to relax > this) > > - 8 bit precision is good enough for all blending
By that you mean interpolation in texture lookups I take it, and the stuff in the TextureFilter() and Blend() routines? > - Need to double check for any overlooked multiplies > > So: > > Interpolation correction: 4 > (16 interpolants / 4 clocks) > > Perspective reciprocal: 2 > (1 reciprocal x 2 pixels) > > Perspective correction: 30 > (15 parameters x 2 pixels) > > Not allocated: 4 > ---- > Total: 40 dedicated 18x18 multipliers > > This will deliver 2 pixels/clock most of the time, but will stall up to > 3 clocks on short spans. Worst case is to fill the screen with single > pixel vertical strips, which will cut the fill rate by 75%. Typical > throughput reduction should be much less, perhaps in the 5-10% range. > If there really are four multipliers left over, they could be applied > to cutting the span setup stall to a single clock. > > Comments/flames? I may be able to do the reciprocal without dedicated multipliers at all, but I'd already mentioned that in my other post. Lourens _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
