RE: [Algorithms] Yet another stencil shadow question

[Chris B. (BUNGIE) <cbu...@mi...>]

Jon's suggestion requires duplicating vertices whenever their face
normals differ. In a typical dense mesh, this will blow your vertex data
size by a factor of six, and require the creation of degenerate quads
between every pair of adjacent non-coplanar triangles. Also, your vertex
cache reuse will go through the floor since every vertex is basically
unique.

It's not necessarily a bad technique, but you should be aware of the
caveats before you decide to go with it.

--
Chris Butcher
Rendering & Simulation Lead
Halo 2 | Bungie Studios
bu...@bu...


-----Original Message-----
From: Tomasz Rozen [mailto:Tom...@in...]=20
Sent: Thursday, December 19, 2002 2:08 AM
To: gda...@li...
Subject: Re: [Algorithms] Yet another stencil shadow question

Okay, thanks for all your answers.

In my previous post I forgot to mention that this algorithm included
inserting degenerated triangles along sharp edges (two per edge).
Basicaly I was expecting something Jon and Chris have described. I think
you
can also have problems with convex meshes.

I think I'll go with what Jon suggested, however I'm a little worried
about
video memory.

Thanks again,
Tomek



> -----Wiadomosc oryginalna-----
> Od: gda...@li...
> [mailto:gda...@li...]W imieniu Jon
> Watte
> Wyslano: Thursday, 19 December 2002 05:39
> Do: gda...@li...
> Temat: RE: [Algorithms] Yet another stencil shadow question
>
>
>
> You don't get a perfect fit with the mesh silhouette, so shadows are
> slimmer than they'd otherwise be. For really coarse geometry, it may
> potentially mean fairly gross shape differences.
>
> If you're not geometry throughput bound, and you very likely are not
> when you do stencil shadows, I'd rather use a separate version of the
> mesh with stitched sliver triangles between each edge, and face
> normals. Extrude all vertices that have (face) normals pointing away
> from the light (or even those pointing ever so slightly towards the
> light).
>
> Cheers,
>
> 				/ h+
>
>
> > -----Original Message-----
> > From: gda...@li...
> > [mailto:gda...@li...]On Behalf Of
> > Tomasz Rozen
> > Sent: Wednesday, December 18, 2002 1:16 PM
> > To: Gdalgorithms-List
> > Subject: [Algorithms] Yet another stencil shadow question
> >
> >
> > Once I've heard about an approach to rendering stencil shadows (but
> > unfortunately I don't remember where). The algorithm was simple:
extrude
> > every vertex if L . N < 0 (L - light vector, N - vertex normal).
> > Has anyone successfuly implemented this algorithm? Are there
> any caveats?
> >
> > Thanks,
> > Tomek
> >
> > --
> > mailto:tr...@st...
> > http://trozen.w.interia.pl
> >
> >
> >
> >
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