Hi fraser, is it possible for you to post the model that you are trying to fillet?

Fillet does not like to have things like little tiny edges or edges broken up into many segments when they could be a longer single edge.

You could try the Merge command (which you need to type in by pushing Tab and then type "Merge" and push Enter) which will glue fragmented edges that touch each other smoothly into longer edges.

Another possibility for getting a fillet in some difficult situations is to use the surface/surface filleter instead of the edge-based filleter.

To use the surface/surface filleter, you use Edit/Separate to break your object down into individual surfaces and select 2 surfaces and then run the Fillet command.

That does a somewhat different mechanism for calculating the fillet which analyzes the surfaces more directly to generate it rather than trying to follow along the edges. The edge-following one can be more convenient since it can do things like build corner patches where several edges come together, the surface/surface one does not do things like corner patches.

But the edge-based filleter has a more difficult job to do so it can get confused and fail somewhat more easily than the surface/surface filleter.

It's hard to give very specific advice about this by just looking at a screenshot instead of examining an actual model though.


Filleting in general has a lot of difficult calculations that it needs to do so it is pretty easy for it to fail if you've got problematic geometry like little slivery surfaces, tiny edges, lumpy or bumpy surfaces, surfaces that fold back on top of themselves or have self-intersections. Also surfaces that touch each other with only a slight crease between them (instead of touching smoothly or more distinctly sharply) can tend to be difficult.

If I could examine your model that would help me to see if you are running into any of those kinds of things.


- Michael