Re: Multiple calls to pfDraw()
Angus Dorbie (dorbie++at++sgi.com)
Thu, 04 Jun 1998 10:41:15 -0700
P J Narayanan wrote:
>
> Hi friends,
>
> I have a question for the experts out there. Sorry if this is an already
> thrashed issue on this group. I couldn't find any references to this
> issue in the FAQ.
>
> I am trying to write a driver for a stereo display device that takes the
> odd video lines as left-eye input and the even ones as right-eye input.
> I modified the perfly Draw callback to set the channel view to the left
> eye location first, call pfDraw(). This is immediately followed by a
> change of channel view to the right eye location/angle and a second
> call to pfDraw(). {OpenGL stencil bits are used with appropriate stencil
> function to make sure the first call writes only the odd lines and
> vice versa).
>
> This scheme, unfortunately, doesn't work well. Both pfDraw() calls seem
> to draw it to the right eye, strangely. I am sure I am missing something
> and would appreciate to be enlightened. Thank you.
>
> Is there any relevant sample code out there that makes multiple calls
> to pfDraw() within the Draw callback, as in multisample antialiasing?
> On a related note, are there examples of drivers for this style of
> stereo and/or the standard SGI style of stereo for the Performer?
Your stencil mode may be getting clobbered by the pfLayer state
when it makes the gl calls.
Use the displace method for decals. You can do this by setting
PFSTATE_DECAL
and turning the override for this state on.
Cheers,Angus.
--
"Only the mediocre are always at their best." -- Jean Giraudoux
For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/
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on Mon Aug 10 1998 - 17:57:30 PDT