Project to surface / Intersection issues

Hi, this issue originally arose in a grasshopper definition where I was projecting thousands of circles on to a wavy surface, however, it appears to be an underlying issue with rhino’s intersection algorithm (or perhaps a mathematical problem with my particular surface). In the attached file, I have simplified the problem to a surface and a cylinder. When you run the “intersect” command, it generates only 3/4 of the circle on the surface. There are several points around this surface where this happens. Any ideas what is causing this?

Thank you!
131125 Project Bug.3dm (546.5 KB)

Hi Steven- This does look like a bug in the intersector to me- if you rotate the cylinder on its centerline a little =, to get the knots at the quadrants off the wavy surface, it works. You can also InsertKnot on the cylinder, in the V direction, Automatic (once) and it will work. Thanks for sending this example, I’ll get it on the pile.


Thanks Pascal! Do you think this will be fixed in the next release?