## HELP: Intersection of B-Spline Surfaces

### HELP: Intersection of B-Spline Surfaces

Dear all,

We are working on a Surface modeller project and we
deal with B-spline surfaces. The following problem
is to be solved and we do not have many good references
to concrete work done in this area.

Problem: Intersection of two B-spline surfaces
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given two B-spline surfaces (BSS), we want to find
the curve formed by the intersection of the two surfaces.
The representations of the resultant curve may be
piecewise linear curve or composite Bezier curve.

The issues we are struggling with are
i.   Algorithm for performing surface X surface intersection
ii.  Tolerance measure for distance
iii. Special cases where the boundary of one surface
touches other surface. The word "touches" has some
distance tolerance associated with it.

We are looking for some references to survey papers,
specific work done.

and I'll post a summary of replies.

Thank you.

Dinesh Shikhare

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National Centre for Software Technology (NCST)
Juhu, Bombay 400049,
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Hi,

My math is a bit (quite a bit?) rusty. I need to calculate the
intersections of two conics, in 2D, of the general form:

ax^2 + 2bxy + cy^2 + dx +ey +f = 0

If it makes it easier one of the conics can be in the form:

x^2/b^2 + y^2/a^2 = 1

I would just adjust the one conic so its position remains the same
relative to the other. I am primarily interested in ellipses if this
makes the problem easier.

Also, does anyone know of any reference material on intersecting
conics, B-splines, and nth degree Bezier curves with one another?

Any help would be greatly appreciated. Thanks
--
Andrew
Ditek International Inc.