the best reference I found on this topic is here: http://chimera.labs.oreilly.com/books/1234000001814/ch08.html#BumpMapping
2016-05-19 14:18 GMT+02:00 Christian Buchner <[email protected]>: > > In the mean time I've learnt a bit more about the limitations of DOT3 bump > mapping. This also explains why this isn't used much anymore. > > - It works in object space, as opposed to shader based models which work > in tangent space. > > - There is a requirement to fully uv-unwrap the model so each point on the > object maps to a unique texel (you can't even exploit symmetries in the > object) > > - One needs to encode the light vector as vertex colors (light position > relative to each vertex, which is very important for point lights). This > means updating the color array whenever the light source moves. > > - The UV maps have to be baked in object coordinates. You can't use bump > maps created for tangent space or the lighting will be incorrect. > > - lots of limitation in the fixed function pipeline (ambient and specular > lighting might be impossible in combination with DOT3) > > Christian > > > > 2016-05-19 12:52 GMT+02:00 Robert Osfield <[email protected]>: > >> Hi Christian, >> >> Thanks for the example. I've merged it with OpenSceneGraph-Data and >> used the git author set to your name/email, looking at github this >> means it links automatically with your git account. I hope this is >> OK. >> >> Thanks, >> Robert. >> >> >> On 10 March 2016 at 16:20, Christian Buchner >> <[email protected]> wrote: >> > >> > It appears there is almost no working example of an OSG object that >> uses the >> > fixed function pipeline DOT3 bump mapping technique. >> > >> > I am attaching an .osg file that features an animated light source that >> > highlights the effect. In osgviewer rotate the box 90 degrees to the >> side >> > for best effect. >> > >> > This is based on a really ancient forum posting from 2008, the OSG file >> was >> > manually cleaned up, removing unnecessary transparency and blending >> effects. >> > http://delta3d.org/forum/viewtopic.php?showtopic=12622 >> > >> > The stone wall texture and bump map was taken from this osg example >> > repository: >> > >> https://bitbucket.org/kornerr/osg-deferred-shading/src/2b2f5532f41c305b31c46467291281388657b392?at=default >> > >> > Any other pairs of diffuse and normal textures might work just as fine. >> Even >> > if this does not make it into the OpenSceneGraph-Data repository, this >> > posting will hopefully preserve the example for another 10 years ;-) >> > >> > Christian >> > >> > >> > _______________________________________________ >> > osg-submissions mailing list >> > [email protected] >> > >> http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org >> > >> _______________________________________________ >> osg-submissions mailing list >> [email protected] >> >> http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org >> > >
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