Hi all!
This year's GSoC is coming to an end in a few days. During the past three
months I focused on the NURBS Intersection project, and finally make NURBS
boolean evaluations available in BRL-CAD. I kept updating my development logs
daily, and uploaded several images to share my progress with everyone. The
link: http://brlcad.org/wiki/User:Phoenix/GSoc2013/Reports
I'd like also post a brief summary here:
A brief look: the brep command now can both provide the conversion of a COMB
with NURBS boolean evaluations and the old routine (CSG tree + brep primitives)
with "--no-evaluation" flag. This can be easily used to test on some sample
geometries, such as csgbrep.g, arb_intersect.g or some larger dbs like world.g,
bldg391.g.
In my development logs you can see some raytrace results of boolean evaluations
on some basic primitives (arb8 and ehy, tor and sph, etc.)
Before mid-term evaluations I wrote the ON_Intersect() routines for P/P, P/C,
P/S, C/C, C/S and S/S, and continued to fix some bugs after mid-term when
developing the evaluation functionality. The intersections proved to work even
with the extreme_ssi test. Some lower level intersections are used in the upper
ones (for example, C/C is used in C/S and S/S). For detailed descriptions, you
can go to include/brep.h. :) The most challenging work is certainly to deal
with the overlaps in SSI...
After that boolean evaluation was developed based on the NURBS intersections.
It includes splitting a trimming face, inside/outside tests and forming the
final b-rep structure. Connectivity graphs is disabled finally (although have
spent lots time to implement it) because its speedup is not critical
(inside/outside tests don't take too much time compared to other computations).
I really learned a lot from this project, and hope my work can make BRL-CAD a
more powerful CAD software with better NURBS processing functionality. Even
after GSoC finishes, I'll stay in BRL-CAD, and help improving the NURBS parts
(or some others if needed).
Comments are welcomed... Just click the link above and see the result images!
Cheers!
Wu
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