Angus Dorbie (dorbie++at++multipass.asd.sgi.com)
Tue, 15 Jul 1997 19:28:11 -0700
There's just a view orientation difference. So there's no conversion,
there will be a pre viewing 90 degree rotate around x on the mviewing stack
so conceptually y & z mean different things.
As I've said this is for the z up coordinate system imposed by performer.
So
pf_x == gl_x
pf_y == -gl_z
pf_z == gl_y
gl_x == pf_x
gl_y == pf_z
gl_z == -pf_y
If you really insist on using gl coordinates you can add a pfSCS above
the scene graph with a 90 degree x rotate and pre & post multiply the
viewing matrix by +ve & -ve 90 degree x rotations. If you do this
then conceptually you end up with OpenGL style coordinates in all
Channel, DCS & SCS matrices.
This is what I did with Divisions Performer implementation of dPL you
may be familiar with, and why the implementation is able to easily
handle the Y = up coordinates of dPL.
There are simpler ways but performer coordinate stuff like the
isector partitioning & earth sky would suffer as a result (if you
decided you needed them).
BTW I think there is also me a row vs column difference for OpenGL, I'm
not sure about this. But it's easy to figure this part.
Cheers,Angus.
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