Bernard Leclerc (bleclerc++at++cae.ca)
Thu, 18 Jan 1996 14:23:03 -0500
First, I'd like to thank those of you who sent me comments concerning the
posting entitled "Real-Time Depth-of-Field Image Processing". So, thank you
Angus Henderson, Ken Lindsay, Javier Castellar and Remi Arnaud.
Since almost everybody suggested to approach the depth-of-field problem using
multipass rendering, we tried again this approach as described in the OpenGL
Programmer's Guide in the example dof.c
Here are the timing we've observed while using the accumulation buffer:
acbuf(AC_CLEAR, 0.0f) 0.5 ms
acbuf(AC_ACCUMULATE, 1.0f/n) 2.0 ms
acbuf(AC_RETURN, 1.0f) 3.5 ms
Note that these timing were obtained under the following frame buffer
configuration:
RBGsize(12);
zbsize(32);
mssize(8,24,1);
screen resolution: 640 x 480
Now is the time for the question:
How come it takes longer to RETURN the accumulation buffer to the
normal frame buffer than it takes to ACCUMULATE the normal frame buffer into
the accumulation buffer?
I'm kind of surprised by the result. I had expected a smaller (or equal) amount
of time necessary to return the acbuf than the time necessary to accumulate.
How come it's the other way around?
Could someone shed some light on acbuf operations? Please...
--
___/ | ___/ Bernard Leclerc e-mail: bleclerc++at++cae.ca
/ / | / Systems Engineer voice: +1 514 341 2000
/ / | __/ CAE Electronics Ltd. extension 2275
/ / | / 8585 Cote De Liesse fax: +1 514 340 5496
/ ____ | / P.O. Box 1800
_____/ _/ _| _____/ Saint-Laurent, Quebec, Canada, H4L-4X4
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