Remi Arnaud (remi++at++remi.asd.sgi.com)
Wed, 14 Aug 1996 11:04:40 -0700
> In the scenario below the decal2 will show through base1 & decal1 if you
> draw base1 & decal1 first. This is what I meant by "occlusion between
> decal surfaces", I didn't mean decals on the same base.
>
>
> Eye decal1 & Base1 decal2 & Base2
> | |
> | ||
> | ||
> <) || ||
> || |
> | |
> | |
>
> With one stencil bit this problem is unavoidable.
>
> This wouldn't be a problem if you have more that 1 stencil plane because
> by changing operations b and e where you render and test against a stencil
> value which increases with each base & layer set.
> To avoid confusion, I don't mean a stencil increment operation, just
> increment the write and test value for each decal & base set.
>
This case should work anyway:
If you render the base2 ploygon after the base & layer 1, the z test fail for
every pixel of the base2 polygon. As a result, the stencil is zeroed for all
pixels covered by the base2 polygon :
glStencilFunc(GL_ALWAYS, 1, 0x01);
glStencilOp(GL_ZERO, GL_ZERO, GL_REPLACE);
So the layer2 polygon will not affect any pixels, unless it is not contained
inside the base2.
-- Remi
--
o o Remi ARNAUD - Silicon Graphics, Performer, Advanced Systems Dev o o o o Mail Stop 590 - 2011 N. Shoreline Boulevard, Mountain View, CA94043 o o o o Email: remi++at++asd.sgi.com - Tel: (415) 933 6208 - Fax: (415) 965 2658 o o
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