Re: Is this possible ??
Rob Jenkins (robj++at++quid)
Tue, 1 Oct 1996 11:40:54 -0700
On Oct 1, 10:40am, Janet Estabridis wrote:
> Subject: Is this possible ??
> Anyone,
>
> System: RE2 XRIX 5.3
>
> I have a my scene which I am flying through. I am constantly doing range
> calculations on the z-buffer with multisampling off and shipping them off
> to other processors. I get some feedback from these processors and I would
> like to mark an x,y location in my scene, every frame, with a crosshair or
> colored dot that will not mess up my z-buffer scene range calculations.
> So, I have two questions:
>
> 1. Is there a way to have the crosshair not interfer (i.e., if it is in
> front to be seen, it will definitley be in the zbuffer if I use the common
> method) ??
>
> 2. What would anyone suggest as a "nice" way and "the fastest way" to draw
> the crosshair or colored dot in my draw callback routine even if it
> interfers?? Is OpenGL in the draw callback routine going to be the
> fastest?
>
> Thanks, I've only been at this stuff for a month and a half and I am
> finding everyone very helpful.
>
> Janet Estabridis
> Code 4722E0D
> NAWC China Lake, CA (619) 939-6984
>
>
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>-- End of excerpt from Janet Estabridis
Hi
See the FAQs for a description/example code of using a post draw call back.
It's probably more efficent for you to just change the zbuffer state 'around'
the drawing of the crosshairs than draw to the overlay planes. If you render
with IrisGL, something like this:
zfunction(ZF_ALWAYS);
zwritemask(0x0);
draw crosshairs
zfunction(ZF_LEQUAL);
zwritemask(0xffffffff);
in you call back will ensure the crosshairs are always over your scene, for
OpenGL sustitute:
zfunction( func ) --> glDepthFunc( func )
zwritemask( mask ) --> glDepthMask( boolean )
Cheers
Rob
PS you can get to the FAQs via the web page
--
________________________________________________________________
Rob Jenkins
Silicon Graphics
robj++at++csd.sgi.com
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