On Jan 27, 2010, at 9:35 AM, Tom Browder wrote: > On Wed, Jan 27, 2010 at 07:57, Clifford Yapp <[email protected]> > wrote: > ... >> Tom, that refers to raytracing. Tessellation is a separate step, >> one that's >> on the list but isn't (yet) at the top of the priority heap. > ... >> I should note there isn't much in the way of dependencies here - >> any of these >> tasks can be worked more or less independent of the others. It's >> just a >> question of where resources get allocated, and right now step >> importing has >> priority (otherwise the only way to import NURBS is the 3dm-g >> path, which has >> its own issues - gotta have 'em in BRL-CAD before we can do much >> with 'em). > > Thanks for the input, Cliff. > > I'm really interested in the idea Sean mentioned some time ago that > the nurbs primitive will aid the conversion process from CSG to BREP. > Is or will there be a way to convert other CSG primitives to nurbs as > an intermediate step? > > -Tom
Tom, NURBS will definitely aid in the conversion process. For many users, the entire problem of polygons and tessellation can be avoided. When the original CAD data is coming in from a system like Pro/Engineer, their internal format is basically a NURBS parametric format. With the step-g or 3dm-g importer bringing in NURBS objects directly, polygons are no longer necessary other than for visualization (or export/conversion to still other polygonal formats). Cliff Yapp and Ben Poole worked on implementing the conversion support to turn all of our CSG primitives into NURBS. Cliff got pretty much got them all done last year minus a few details and quick hacks that will need to be sorted out later. The longer pole in the tent, though, is the boolean evaluation portion. Consider two boxes side-by-side unioned together. So right now, the boxes themselves can be converted from our traditional implicit form into a NURBS explicit form. Without boolean evaluation, though, the boxes can't be stitched together and you end up with the two side-by- side "interior" faces remaining. So, we're closer, but there's still another piece remaining. We have to be able to perform surface-surface intersection calculations, then stitch together a resulting surface after a given boolean operation on two objects. Cheers! Sean ------------------------------------------------------------------------------ SOLARIS 10 is the OS for Data Centers - provides features such as DTrace, Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW http://p.sf.net/sfu/solaris-dev2dev _______________________________________________ BRL-CAD Developer mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/brlcad-devel
