Re: Scene Density Requirements
Jude Anthony (jude++at++p3.enzian.com)
Fri, 10 Jan 1997 15:17:46 EST
> 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.
The polygons and the observer are placed in such a way that one database unit
(meter) is one on-screen pixel. (The TTPRR specifies pixels.) They are
layered more-or-less like this:
+-----------+
| +-----------+
| | +------------+
+ | | |
+ | |
+------------+
So that the strips are never more than 6 deep.
Later,
Jude Anthony
jude++at++p3.enzian.com
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on Mon Aug 10 1998 - 17:54:19 PDT