I didn't know software rasterizer was used... hmm, but thinking about it, it makes sense as retrieving info from the GPU has not always been an easy thing, yet selection buffer exists since a very long time. Anyway, as you said, higher level knowledge of the scene is definitely an advantage. I'll try to reproduce the same configuration (selecting a square of given width around the click in view space, think I saw a pyramid-like intersection primitive for doing this in OSG) as I did before with selection buffer.
Thanks for that info, Raphael On Feb 12, 2008 2:52 AM, Paul Martz <[EMAIL PROTECTED]> wrote: > - 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 > 303 859 9466 > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > >
_______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
