When I shade these surfaces, I can see an intersection; however, the curve from intersection command only creates a curve of the circle and a small section where the radius and straight surfaces meet. If I extrude a curve from the top of the radius surface, I get a different result, which I can mirror to get a complete curve. Why are the results inconsistent? How do I create these surfaces, so that the curve from intersection command gives a complete curve?

Hi Marcus - yep - this is a hard case, for one thing the surfaces gradually become coincident - in itself this makes it pretty difficult to find a clean intersection for the full distance, but there is something else going on here as well - for now, try this: Rebuild copies of the surfaces to a lot of points - say 24 each way, degree 5, then intersect the results - that gets you much more of the curve you are looking for. Delete the rebuilt surfaces, ExtandCrvOnSrf the curve on the 90 degree surface, or if you get multiple segments (I did in V6, not V7) use Match or BlendCrv to string them togetherā¦

A partial result is also possible if the bent surface is being split with its own isocurve. Fromt here, the blue intersect curve could be extended to the end of the straight pipe with āQuadā snap. Or, alternatively, a blend curve could be added between the blue curve and the green one. Example: