Re: Scene Density Requirements
Rémi Arnaud (remi++at++remi.asd.sgi.com)
Fri, 10 Jan 1997 11:35:20 -0800 (PST)
Jude Anthony wrote:
>
> OK, I'm back again. This question goes to both Performer and Vega groups.
>
> Our TTPRR requires that we render, at 30Hz, a scene with:
> 150 tris, 101x101
> 1350 tris, 51x51
> 1500 tris, 10x10
>
> We're not getting 30Hz at 1024x768.
>
> When we bought the Onyx/RE2, we had 1 RM4. The salesman looked at our
> screen size, projected depth complexity, and iteration rate, and told us we'd
> need to upgrade to 2 RM4s to get the job done.
>
> Our average depth complexity for the scene is somewhere between 3.31 and
> 3.33. My manager tells me the threshold was around 3.1.
>
> The rated pixel fill rate for 2 RM4s is 110Mpix/sec. Our scene contains:
> 150 x 101 x 101 / 2 = 765,075
> + 1350 x 51 x 51 / 2 = 1,755,675
> + 1500 x 10 x 10 / 2 = 75,000
> --------------------------------
> 2,595,750 pixels.
> At 30Hz, that makes 2,595,750 * 30 = 77,872,500pix/sec.
>
> 77,872,500pix/sec is below the rated pixel fill rate. It's even below the
> 90Mpix/sec conservative fill rate on the salesman's sheets.
>
> The problem is to increase the iteration rate to 30Hz. My manager has me
> shifting polygons around, trying to decrease the depth complexity. I'm
> making the attempt, but my experience with renderers tells me this is not
> going to work; the depth complexity is calculated, and is only useful for
> culling and pixel fill estimates. Is this the case, or am I working with a
> different beast?
>
> The current thinking is that there is some Performer bottleneck. Any ideas
> on how to bring the iteration rate up?
>
> The scene is composed of strips of polygons. Perfly shows me that all the
> strips are meshed, all at more than 14 tris/strip. The strips are offset in
> such a way that no more than 6 are ever layered. Each strip is a different
> color than the one above it, so as to facilitate counting (6 colors total).
> There are no textures. The whole thing eventually runs as a vega app.
>
I'm confused. Is your polygon count is the part of the database that is displayed ?
a 10x10 triangle in the database can be full screen after projection, if you have
6 layers, that makes a depth complexity of 6, requiring 141 Mpixels/s.
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on Mon Aug 10 1998 - 17:54:18 PDT