gdalgorithms-list

[Algorithms] volumetric spotlight

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

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

Re: [Algorithms] volumetric spotlight

[Darren G. <dg...@ke...>]

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
><http://www.8monkeylabs.com>www.8monkeylabs.com
>------------------------------------------------------------------------------
>Download Intel&#174; Parallel Studio Eval
>Try the new software tools for yourself. Speed compiling, find bugs
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>See why Intel Parallel Studio got high marks during beta.
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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
>
> ------------------------------------------------------------------------------
> Download Intel&#174; Parallel Studio Eval
> Try the new software tools for yourself. Speed compiling, find bugs
> proactively, and fine-tune applications for parallel performance.
> See why Intel Parallel Studio got high marks during beta.
>  http://p.sf.net/sfu/intel-sw-dev
> _______________________________________________
> GDAlgorithms-list mailing list
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>  https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
> Archives:
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>
>
>
> ------------------------------------------------------------------------------
> Download Intel&#174; Parallel Studio Eval
> Try the new software tools for yourself. Speed compiling, find bugs
> proactively, and fine-tune applications for parallel performance.
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>



-- 
Jeff Russell
Engineer, 8monkey Labs
www.8monkeylabs.com

Re: [Algorithms] volumetric spotlight

[David N. <da...@re...>]

Hi Jeff,

 

Just shooting off an idea that may be useful,

 

I'd imagine you could render the front facing polygons and then the back
facing polygons with depth testing on.  That difference in depth of the
two distance the light travels through the cone at that point. You could
then use that information to calculate how much light scattering has
occurred.

 

-= Dave

 

From: Jeff Russell [mailto:je...@8m...] 
Sent: Wednesday, March 24, 2010 12:53 PM
To: Game Development Algorithms
Subject: Re: [Algorithms] volumetric spotlight

 

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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	Try the new software tools for yourself. Speed compiling, find
bugs
	proactively, and fine-tune applications for parallel
performance.
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------------------------------------------------------------------------
------
Download Intel&#174; Parallel Studio Eval
Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev
_______________________________________________
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t




-- 
Jeff Russell
Engineer, 8monkey Labs
www.8monkeylabs.com

Re: [Algorithms] volumetric spotlight

[Bob <ma...@di...>]

If you are using the texture-based method, an additive blend would be more effective than an alpha blend or mask.

--B
  From: Darren Grant 
  To: Game Development Algorithms ; Game Development Algorithms 
  Sent: Wednesday, March 24, 2010 2:19 PM
  Subject: Re: [Algorithms] volumetric spotlight


  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
    ------------------------------------------------------------------------------
    Download Intel® Parallel Studio Eval
    Try the new software tools for yourself. Speed compiling, find bugs
    proactively, and fine-tune applications for parallel performance.
    See why Intel Parallel Studio got high marks during beta.
    http://p.sf.net/sfu/intel-sw-dev
    _______________________________________________
    GDAlgorithms-list mailing list
    GDA...@li...
    https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
    Archives:
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------------------------------------------------------------------------------


  ------------------------------------------------------------------------------
  Download Intel® Parallel Studio Eval
  Try the new software tools for yourself. Speed compiling, find bugs
  proactively, and fine-tune applications for parallel performance.
  See why Intel Parallel Studio got high marks during beta.
  http://p.sf.net/sfu/intel-sw-dev

Re: [Algorithms] volumetric spotlight

[Sebastian S. <seb...@gm...>]

Try this one:
http://www.vis.uni-stuttgart.de/~dachsbcn/download/espmss10.pdf


On Wed, Mar 24, 2010 at 4:24 PM, Jeff Russell <je...@8m...>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
>
>
> ------------------------------------------------------------------------------
> Download Intel&#174; Parallel Studio Eval
> Try the new software tools for yourself. Speed compiling, find bugs
> proactively, and fine-tune applications for parallel performance.
> See why Intel Parallel Studio got high marks during beta.
> http://p.sf.net/sfu/intel-sw-dev
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
> Archives:
> http://sourceforge.net/mailarchive/forum.php?forum_name=gdalgorithms-list
>



-- 
Sebastian Sylvan

Re: [Algorithms] volumetric spotlight

[Bert P. <be...@bp...>]

Darren Grant schreef:

> 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.

I'd give that a try too.  There's some good shadowmap based stuff in
ShaderX7 as well for easier integration with scene geometry (p. 331).


Also check out I3D10's update to Crytek's Light propagation volumes.


hth,
bert

Re: [Algorithms] volumetric spotlight

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

OP here, thought I'd share my results. Thanks to Miles in particular for
being helpful.

http://i44.tinypic.com/2h4algx.jpg

Determined the distance through the fog cone by tracing the eye vector to
the far side of the cone, then clipping that distance against the depth
buffer. With the entry and exit points inside the volume, it turned out to
be fairly easy to evaluate the falloff integral implicitly. All told
compiles into about 50 shader instructions, one texture lookup, and no
overdraw. I might be able to squeeze the shader down a little more, but that
will come later.

Thanks guys,

Jeff

On Sun, Mar 28, 2010 at 9:18 AM, Bert Peers <be...@bp...> wrote:

> Darren Grant schreef:
>
> > 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.
>
> I'd give that a try too.  There's some good shadowmap based stuff in
> ShaderX7 as well for easier integration with scene geometry (p. 331).
>
>
> Also check out I3D10's update to Crytek's Light propagation volumes.
>
>
> hth,
> bert
>
>
> ------------------------------------------------------------------------------
> Download Intel&#174; Parallel Studio Eval
> Try the new software tools for yourself. Speed compiling, find bugs
> proactively, and fine-tune applications for parallel performance.
> See why Intel Parallel Studio got high marks during beta.
> http://p.sf.net/sfu/intel-sw-dev
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
> Archives:
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>



-- 
Jeff Russell
Engineer, 8monkey Labs
www.8monkeylabs.com