Re: [Algorithms] volumetric spotlight

[Jeff R. <je...@8m...>]

That third option is kind of what I'm leaning toward - ray tests vs a cone
are mathematically simple, so that combined with a screen depth lookup
(already available) I'm hoping to be able to swing something cool today.

Jeff

On Wed, Mar 24, 2010 at 2:19 PM, Darren Grant <
dg...@ke...> wrote:

>  I don't have references but here are a few techniques in increasing
> complexity:
>
> For viewers at a distance it is hard to beat the simplicity of billboard
> sprites. Just lock a billboard to the spotlight cone axis and use alpha
> blending to make the texture glow. Fade it out when the viewer gets close
> enough to make the effect cheesy.
>
> Create an umbra mesh, a skirt that resembles the spot cone and fix it to
> the spotlight in space. Simple vertex coloring to fade the skirt at the far
> end can be very effective. Again render using alpha blending. Some simple
> pixel shader work using normal averaging and dot product can help to hide
> the edges of the mesh. If you have access to the depth buffer values, you
> can also fade out pixels that approach the near plane so they don't clip
> noticeably as the viewer passes through the cone.
>
> The most complex approach is to write a ray-casting shader that integrates
> over distance travelled by each eye ray through the umbra volume. It is hard
> to get the results to overlap and intersect correctly with the rest of the
> scene unless you have some sort of unified rendering architecture built
> around ray-casting. Very pretty if you get it working, but very difficult to
> deploy without limitations coming back to get you later.
>
>
> Cheers,
> Darren
>
>
>
>
>
> At 09:24 AM 3/24/2010, Jeff Russell wrote:
>
> Hey, anybody have any cool reference for how to render a volumetric
> spotlight effect? I realize that full correct shadowing with volumetric
> lighting might be kind of heavy duty, so I'm willing to try something a
> little dirtier or with no shadows.
>
> Regards,
>
> Jeff
>
>
> --
> Jeff Russell
> Engineer, 8monkey Labs
> www.8monkeylabs.com
>
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-- 
Jeff Russell
Engineer, 8monkey Labs
www.8monkeylabs.com