Claus-

thanks, I appreciate your help! that said, I don't know where that leaves me. attempting to "fix" problematic geometry that isn't understood without your knowledge, expertise, and experience doesn't seem like an attractive solution............. yes, I can extend surfaces, avoid boundary intersections, and displace source curves BUT what happens the next time a discontinuous curve results in spite of the precautions?? at the end of the day, I need to get to a dependable brute force (think D-8 or D-9 Caterpillar) self sufficiency solution that takes longer and isn't clever, elegant, or inspired like the work done by people like you that do this full time for a living!! conceptual design, NOT production design or something to hang in a gallery!!

Art
artesmith@earthlink.net

Hi Art
I made a quick video showing how to create a surface from projected curves.

http://www.csi-concepts.com/Demo/videos/trimSurf.mp4

Some notes/observations:

--The projection of the single ellipse into multiple segments is because the ellipse projects to the exact edge of the surface. At that exact point,there is no curve definition so ACIS creates multiple curves. If these additional segments are troublesome, use the Surface Extend and select the face to extend all sides of the surface a small amount.

--Generally you will get a smoother surface by trimming to an existing surface then recreating a cover surface over a reference surface. For example in the industry I came from, you would generally over extend your surfaces, and trim back to the intersection. I'm not sure this applies to your example but perhaps it might help on another task.

--I didn't see a guide curve in the file,so I just created a cover surface in the video. It actually created a pretty smooth surface when I checked zebra stripes.

--In the video I show using the Surface Boolean Intersection command. I made some corrections in the code to make that work properly in 1187:)

Hope this helps!

Tim

Tim-

what constitutes a valid "guide curve"?? we may be beyond "gaps", but it doesn't feel very far...

Art
artesmith@earthlink.net