Hi, Im currently working on what is basically the same problem. We want to be able to have more than 8 lights in a scene and we want objects to be lit by the N most influential lights.
We have decided not to support fixed function pipeline. Instead of osg::LightSource/osg::Light we have a single custom Light node that is registered with our LightManager. Each object that is lit queries the lightmanager for the N most influential lights, similar to what your doing. Uniforms are set based on the lights (gl_LightSource is not used) and the shader loops over lights. //Shader pseudo code for each light L in lights if L is directional do directional_light else if L is point do point_light else do spotlight The last part is not fully implemented yet and im a bit worried about how it will perform. Currently the uniforms are set during the cull traversal by using a callback on the drawables, but im not sure that this is the best or even a good way of doing it. Is it better to do a a separate traversal by implementing a NodeVisitor? /Andreas Lindmark 2008/10/13 Daniel Rowe <[EMAIL PROTECTED]> > Hi everyone, > > This is my first post to osg-users, and I'd like to thank everyone who has > contributed to OpenSceneGraph. I have found it to be indispensable. > > Currently I am modifying a Delta3D-based engine to select the most > influential lights around an object, to allow our artists to place any > number of lights in a scene without being restrained by the usual cap of 8 > lights. > > The algorithm is as follows: Upon being added to the scene, LightSources > register themselves with the LightManager. Each lit object queries the > LightManager for the 4 most influential lights (based on proximity and light > intensity) during the Update traversal and assigns the appropriate shader to > the node, such as the 1 directional 1 spot 2 point light shader, the 2 > directional 0 spot 1 point light shader, etc. > > The final problem I have to solve is to figure out how to get the correct > lights into the correct order that the shaders will expect them in. I want > to be able to ignore the default light number of the 4 light sources I'm > using and be able to set them manually. However, this has proven difficult, > since many lights will need multiple different indices, and assigning this > in the update callback as I had originally planned would mean that every > change except the last one would be overwritten. > > My first option is to write shaders with a list of uniforms for each light, > and set the uniforms in the expected order. I have shied away from this > approach for now to avoid bloated shaders, since GLSL has built-in uniforms > for OpenGL lights. > > The second option, from what I've gathered, is to leverage > osgUtil::RenderStage. As I see it, I'm going to need to clone the lights > (managing them myself without adding them to the scene), re-number them > appropriately, and add them to their own RenderStage, which also contains > the lit object. > > I've dug extensively through past threads looking for information on > RenderStage and selective lighting, but unfortunately I'm still somewhat > clueless as to how the back end of the rendering works as a whole. How do > RenderBins fit into this equation? Will I have to find a way to rip the lit > object out of the default RenderStage and throw it into mine? Is this even a > good approach, or is there a more elegant method I could use? Am I missing > the point completely? > > Thanks in advance, everyone! > > - Daniel Rowe > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > >
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