- OpenGL selection buffer seems not recommended as a way of picking in OSG, explicit primitive intersections are used instead. Could someone please comment on this (why...)?
OpenGL's selection render mode is almost universally implemented via software rendering, and is therefore painfully slow for any moderate geometry load. It also tends to be O(n) -- your app just renders everything, even stuff no where near the pick point. You can sidestep these issues by reducing or simplifying the geometry being tested. Selection is the only (sort of direct) support OpenGL has for picking, so if you're using OpenGL and don't want to code a better method, then you're stuck with selection. Fortunately OSG has a superior alternative. One thing scene graphs are good at is spatial organization. As a result, pick testing in a scene graph is O(log(n)). Although it also runs in software, it performs simple ray/sphere intersection tests, which are much more efficient than software rasterization. Paul Martz Skew Matrix Software LLC http://www.skew-matrix.com <http://www.skew-matrix.com/> 303 859 9466
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