Jean-Francois Panisset (panisset++at++discreet.qc.ca)
Fri, 31 Jan 1997 16:54:09 -0500
On an IR driven by R10K CPUs, we have measured sustained rates
of around 170MB/sec when doing 720x486 glDrawPixels() in
GL_RGB, GL_UNSIGNED_BYTE format. You are mostly bound by
the bandwidth between over host to pipe connection, so whether you
use GL_RGB, GL_RGBA, GL_UNSIGNED_BYTE or GL_UNSIGNED_SHORT data types,
the MB/sec bandwidth remains pretty much the same (with correponding
variations in mpixels/sec).
On a RealityEngine2, we see around 79MB/sec for GL_RGB, GL_UNSIGNED_BYTE
OpenGL pixels, about the same for pixmode(PM_SIZE,24) IrisGL pixels.
As others have said: pixels in OpenGL are treated the same as
polygon-generated fragments, so make sure expensive operations
are turned off (including texturing: for some silly reasons,
pixels can be textured, even though there is no way to
specify texture coordinates).
JF
Jean-Francois Panisset panisset++at++discreet.com
Software Engineer
Discreet Logic
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