Hi!
After several weeks' work on the surface-surface intersections, it's improved
significantly and can handle lots of cases that cannot be handled well before.
It's more accurate and correct, ready for the evaluation. (Other intersections
such as curve-curve, curve-surface, point-point, point-curve, and point-surface
are also ready.) I'll still perform tests with some real geometries, such as
the ones in db/*.g. If you are interested, you can go to the log and the images
on my report page: http://brlcad.org/wiki/User:Phoenix/GSoc2013/Reports
The major problem I encounter now is the overlapping cases, that is, two
surfaces have some part overlapping, and we should report the boundary of the
overlap region. As the current approach first computes intersection points, and
then fit them into curves, so it can work well with transversal cases and
tangent cases, but not overlap cases. It's quite hard to get the overlap region
from these points. (For intersection points in the overlap region, the normals
on them of the two surfaces should have the same or opposite direction, which
can be used to determined whether they are inside an overlap region, and divide
them into clusters according to their adjacency, forming the overlap region.
But I think this is not very accurate, because these points are not necessarily
on the boundaries.) Today I have read paper:
http://www.sciencedirect.com/science/article/pii/S0010448596000991, and it
mentions that given two polynomial surfaces, if they overlap over a region, the
overlap region must be bounded by parts of the boundaries of the two surfaces.
Although it specifies polynomial surfaces, but according to the prove, this
seems to be satisfied for all continuous surfaces (C-infinite). If this
property can be adopted, we can have a much simplified and accurate approach,
because we can get the boundary of overlap directly.
So my question is, can we assume that the surfaces are C-infinite? For the
major primitives in BRL-CAD, this seems to be satisfied.
Thank you and look forward to ideas and replies.
Cheers!
Wu
------------------------------------------------------------------------------
See everything from the browser to the database with AppDynamics
Get end-to-end visibility with application monitoring from AppDynamics
Isolate bottlenecks and diagnose root cause in seconds.
Start your free trial of AppDynamics Pro today!
http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk
_______________________________________________
BRL-CAD Developer mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/brlcad-devel
