Trouble Making Fillets (and working with surfaces in general)

Okay so problems like this have been driving me nuts over the course of the last six months as I’ve learned Rhino, but I’m finally at the point where I think I just need some damn help on how Rhino handles this kind of stuff. I’m mocking up a concept for a mixing bowl, and I’m attempting to add a spout feature. The way I’ve done this is by slicing away a section of the bowl and using surface lofts to create the two spout surfaces and closing the top with surface from edges. Everything looks correct but adding fillets to smooth out the shape is basically impossible. if the FilletEdge command produces anything at all it creates fillet surfaces embedded within the still intact main surfaces, and when I try to use the trim tool to clean it up…the trim tool just doesn’t react. I’m constructing this geometry with Rhino’s very own surface tools, where exactly is the problem here coming from?

This is my biggest problem with Rhino I think so far. Commands like Trim or Create Solid will just fail without even an error message, and you just click and nothing happens. I’m spending way more time than I should be just trying to figure out why tools don’t work without any damn feedback.

Check out this thread for some help making forms like this.

In short, if Trim or Split don’t work, it’s generally due to an incomplete intersection curve. Post a specific 3dm file or collection of surfaces and you’ll get more help here troubleshooting.

I’ll look into that for this specific problem, thanks. I’ve attached the 3DM file as well though, if anyone could glance at it, since I’m running into these fillet issues all the time, I guess I just don’t get how “incomplete curves” can be generated by Rhino’s own tools, I’m constructing these lofts with reference specifically to the edge I want to join to.

Bowl Concept.3dm (682.7 KB)

So the issues are several here. For starters, the lip surface is not tangent or continuous with the rest of the rim edge. The surface edges are also not tangent. This creates a kink or sharp spot where the fillet will try to trim against the existing geometry and then join to the result. The additional edge between the rim edge and the lip surface is also not helping as the fillet has to create two fillet surfaces here and trim and join them against one another as well.

Another issue that will cause the fillet to fail to trim and join are the singularities at the junctures of the lip and rim edge. Sweep2 or NetworkSrf might have been used here. These singularities are a zero dimension side of a four sided NURBS surface. In short, they can cause problems. I am fond of saying “less edges, less problems” when surface modeling, so if you can construct the forms made up of multiple surfaces with less surface edges where you want the fillets, you’ll avoid some common pitfalls.

All and all, you can use the surfaces made with FilletEdge (but not trimmed and joined successfully) as a starting point for the surfaces you want. This is complicated to explain so here are two video tutorials I made in the past that might help with some of the techniques I use.

How does Rhino determine what makes a polysurface as opposed to a regular surface? My contour that I’m revolving to form the bowl is a series of splines that have been Joined, but it still creates it as a polysurface with a split between two portions of the outermost surface, which makes editing a spout shape in tricky

I used the smooth tool to create a small curve at that seam tangent to both of them, which is as far as I know how to make the two curves contiguous, what else do I need to do?

You’ll need a single, ‘unexplodable’ curve (no kinks, no stacked CVs) in order to produce a single surface.

Thanks. I’m coming to Rhink from Solidworks, so the idea of “editing” surfaces directly is still pretty alien to me, I want to drive everything based off of the underlying geometry before I create the feature.