From: Paik, Charles C (Charles.Paik++at++MW.Boeing.com)
Date: 01/26/2000 13:35:51
Hi,
I am rendering a scene with 2 different sets of material properties. I
would like to display the scene as if the scene was rendered separately and
additively superimposed. My thought was that the accumulation buffer would
be ideal for this application. I could render each scene independently and
use the accumulation buffer to mix the imagery. However, it seems that
there is a serious performance penalty with the accumulation buffer.
I used an onyx2 at 1280x1024 resolution as a test bed. It seems that it
takes approximately 3.5 ms for each glAccum operation. In my experiments, I
would
1) Render the scene with the first material property to the color buffer,
2) Copy the color buffer to the accumulation buffer,
3) Render the scene with the second material property to the color buffer,
4) Additively transfer the color buffer to the accumulation buffer, and
5) Copy the accumulation buffer back to the color buffer.
There are three transfers between the color and accumulation buffers (Steps
2, 4, & 5). Those three steps have caused an additional 10.5 ms of fill
time. 10.5 ms is a very heavy hit for my application.
My next thought was to render the second scene directly in the accumulation
buffer, and additively transfer the accumulation buffer back to the color
buffer. But I do not know how to do either of those steps. (Or even if it
is possible.)
Can anyone offer any suggestions? I am open to any hints, hacks, or
altogether different approaches. Thanks.
PS Does anyone know how to load tiff files in performer? Thanks again.
-- Charles C. Paik The Boeing Company P.O. Box 516 MC S106-4715 St. Louis, MO 630166-0516email: charles.c.paik++at++boeing.com phone: 314-233-6807 fax: 314-232-4181
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