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
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