RE: [Algorithms] Dynamic lights with static shadows

[Jason M. (A. Technologies) <v-j...@mi...>]

    FWIW, one way that we've been handling this lately is with a 3D texture,
as proposed in a .plan by Carmack once upon a time.  It's nice because the
texture coordinate assignment is easily handled by a texture matrix which
transforms the camera space position to the light's coordinate space.  This
gives you a nice per-pixel distance attenuation term and works equally well
for extended light sources.  There is a demo here (which also does dot3 bump
mapping):

http://www.ati.com/na/pages/resource_centre/dev_rel/sdk/RadeonSDK/Html/Sampl
es/OpenGL/RadeonDotProduct3.html

    Beware of the crazy long URL getting truncated.  Also, beware of the
EXT_texture_env_dot3 usage which I don't think is in the public Radeon
driver yet.  That is, if you play with this app, hack around that for now to
view just the volume light map pass.

                         -Jason




> -----Original Message-----
> From: Jason Zisk [mailto:zi...@n-...]
> Sent: Thursday, November 09, 2000 10:36 AM
> To: gda...@li...
> Subject: Re: [Algorithms] Dynamic lights with static shadows
> 
> 
> > Quake3 is done with a separate pass, which really is a more 
> sensible way
> to
> > go.
> 
> How does the separate pass affect the lightmaps though?  I'd 
> assume you want
> the globe of light to eliminate any shadows under it, is 
> there a blending
> mode that would do this?  Somehow keep the texture 
> information and just
> eliminate the lightmap where there is a texel of light.
> 
> Also, how is the globe of light calculated?  I can't seem to 
> figure that one
> out.  Is it just a texture that looks like a circle of light that is
> projected onto the geometry around the light source?  I can't 
> seem to come
> up with a way that would work for a complex environment and 
> point lights.
> 
> Or do you step through each texel on the lightmap calculating 
> distance to
> the light source?  That would seem slow but easier to 
> program, just need to
> convert the UV on the lightmap texture to world space to 
> calculate intensity
> of the light at that point.
> 
> Thanks,
> 
> - Jason Zisk
> - nFusion Interactive LLC
> 
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