On Mon, 2007-02-19 at 14:35 +0000, Robert Osfield wrote: > Hi Radu, > > On 2/19/07, Radu Mihai <[EMAIL PROTECTED]> wrote: > > I just saw ShadowTexture implementation from svn, I'll look over it and > > maybe get the ShadowMap done following it as a template (looks like the > > place I was got stuck was using different traversal masks for the cull+draw > > traversal). > > I've done a basic port of osgdepthshadow to ShadowMap now too, so svn update > :-) >
Saw it :)
Had to wait for a couple of fixes while I was building, but now [ rev.
6238 ] it works very nicely.
> There is still a lot one could do to improve both ShadowTexture and
> ShadowMap, in few key areas:
>
> - ability to handle wide range of model types - such as some
> objects with textures,
> some without
>
I have done this before, by using a bool Uniform to control the
texturing. On the first implementation, I had a flag when adding to the
scenegraph.
As an improvement, I was thinking of testing the models for texturing
( at addition or update ) , I'm not sure if the steps below are
sufficient :
Visit the model, test each Drawable for StateSet->textureAttribute
and set the Uniform accordingly
Any suggestions for some code that does something similar wold be very
welcome.
> - what happens when multiple lights are used
>
This should be interesting, and very close to PSSM for 1 light.
> - make the same area view dependent so that as you move around a large
> scene
> the part of the scene that the texture covers moves.
>
When using spotlights this is much easier, as the spot's parameters can
be used.
> - use of texture projection that creates a trapezoidal mapping
> rather than a rectangular
> one, I forgot the official name of the technique... the idea is
> create a better balance
> of texels for objects near the eye vs at the far plane.
>
I think there are a couple of names for different implementations of
this [ from GpuGems 1 & ShaderX4 ]:
"Perspective Shadow Maps" [Stamminger02]
"Light Space Perspective Shadow Maps" [Wimmer04]
> There are also technique specific parameters that one could tweak.
>
Bias for the PolygonOffset and bias for SM look-up come to mind.
> ShadowTechnique is never going to be that powerful, ShadowMap will be
> better, but I expect ShadowVolume and ParallelSplitShadowMap to be the
> real high quality solutions. Each of these different techniques will
> have their own strong points/weaknesses.
>
> Since we now have two image based ShadowTechniques checked in I'm
> hoping that it won't take much more to add support for
> ParallelSplitShadowMap.
>
> Robert.
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--
Mihai Radu <[EMAIL PROTECTED]>
Critical Mass Labs
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