From: Angus Dorbie (dorbie++at++sgi.com)
Date: 04/25/2001 03:49:58
Marcin Romaszewicz wrote:
>
> A billboard would work, but you would need to be very careful to draw it
> at the far plane. A better way would be to create your own draw callback
> in which you clear the depth buffer, disable it, draw a textured quad and
> then re-enable the depth buffer. You can avoid clearing the depth buffer
> if you disable the depth test and draw your quad at the far plane. I'm not
> sure which way is faster.
The no depth or color clear with far plane no test & depth write polygon
is faster. This is a relatively old trick for applications which need to
draw a backdrop, you save time by avoiding the clear call. Infact even
if the backdrop has some 3D polygons it can still work and write more
complex depth information to the framebuffer. I think pfEarthSky does
this when it can.
Cheers,Angus.
>
> -- Marcin
>
> On Tue, 24 Apr 2001, Stephane Jaeger wrote:
>
> > Hi ,
> > is there any quick mean/sample that clears the framebuffer to a bitmap
> > instead of a solid color. ( the bitmap being stored in a texture). Do
> > you think that the fastest way to do that would be to use a billboard
> > correctty set ?
> > Thanks,
> > Stephane
> >
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