Re: [Mesa3d-dev] Stencil-related rendering bug?

[Scott M. <mcm...@ca...>]

So far this only happens on my VAIO Laptop running Mandrake 6.0 with
a 2.2.11 kernel and a self compiled version of Mesa 3.2.  It doesn't
happen on my desktop (Mandrake 6.0, 2.2.13, forgot to check which
version of Mesa - oops).

Scott McMillan wrote:
> 
> I am trying to implement a multipass rendering technique similar
> to Mark Kilgard's real-time shadow library, that involves multiple
> rendering passes:
> 
> 1) render the scene with normal lights no stencil
>            glEnable(GL_LIGHT0);
>            glEnable(GL_LIGHTING);
> 
> 2) render the front faces of shadow volumes with the following
>            glDisable(GL_LIGHTING);
>            glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
>            glEnable(GL_STENCIL_TEST);
>            glDepthMask(GL_FALSE);
>            glStencilFunc(GL_ALWAYS, 0, 0);
>            glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
> 
> 3) render the back faces of the shadow volumes with the following:
>            glStencilOp(GL_KEEP, GL_KEEP, GL_DECR);
> 
> 4) render the original scene with a different color light:
>            glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
>            glDepthFunc(GL_EQUAL);
>            glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
>            glStencilFunc(GL_NOTEQUAL, 0, ~0);
> 
>            glDisable(GL_LIGHT0);
>            glEnable(GL_LIGHT1);
>            glEnable(GL_LIGHTING);
> 
> With Mesa, everything works except that I get a white
> translucent (like screen door transparency) haze where the
> shadow volumes are.  This occurs in areas where the stencil
> values were incremented and then decremented back to zero
> so there should have been no rendering into the color buffer
> after the first step.
> 
> This does not happen on SGI's or most NT drivers.
> 
> Anybody have any ideas?  Should I also report this as a bug?
> 
> scott

-- 
Scott McMillan                        mailto:mcm...@ca...
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