left - projecting a line to the sphere
right - intersection a planar surface with the speher
projecting a line to a sphere, or intersecting a planar surfaces with a sphere result in a bulky curve, even if it should be an exact circle.
it seams that a surfaces knows that it is spherical
it seams that a plane knows wether it is planar or not
and there is a Plane-Sphere-Intersection
… so why don t we get a proper result ?
kind regards - tom
i am not sure what the issue is, i assume that the intersection algorithm does not automatically convert the result into a degree 2 curve (circle) because that may not be what everybody wants.
when i project a line to a sphere i get a degree 3 nurbs curve. you can then use SimplifyCrv on the resulting curve and it will convert it to a circle.
Are you assuming that when Intersect is used in Rhino a sphere and a circle as input then the Plane-Sphere-Intersection method in Rhino common would be used in place of the more general method for intersection?
Or do you know that the Plane-Sphere-Intersection method is being used, and are asking why the result is not a circle type object?
I am quite sure that if the method Plane - Sphere - Intersection exists it also is available in the C++ / Rhino Core. So your first statement (yes) is what I assume - why is a general method (nurbs-Surface to nurbs Surface ? used instead of a specific, precise method.
Hi Tom - that is a good question - I don’t know the answer but I’ll guess that this type of special-casing, perhaps, takes too long, or was thought to at one time, but let’s ask @GregArden , he knows for sure.
-Pascal
