Hi Sevy, is it possible for you to post your model file that you're having problems with so I can see what is going on for your particular situation?

There are many possible things that can go wrong with Fillet - things like if there is self-intersecting surfaces in the area to be filleted, if you're trying to do a fillet of a larger radius than there is available room for it to fit. Also some situations like if you have edges that come close to being smooth to one another but actually something like 5 degrees off of tangent instead of actually smooth can make things more difficult for the filleter.

It's hard to know what particular kind of problem you might be running into without seeing the model file.

> Maybe something else allowing us to intervene on the
> previous Actions...

It is possible to remove the surfaces from a previous boolean operation - for that you delete those faces and then do some "untrim" operations on the areas that were cut to restore the original underlying surfaces there. Sometimes you then may need to retrim the surfaces.

There is a tutorial on that kind of object repair mechanism here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17


Fillet though is in general a sensitive operation - it involves a sequence of complex operations like producing offset surfaces, intersecting those surfaces to build fillet rails, building fillet surfaces, intersecting those fillet surfaces with each other where they collide, and building corner patch areas. Each of those operations is pretty complex. So Fillet does not tolerate messy geometry very well. If you get extra lines appearing, that can mean that the stage of intersecting fillet surfaces with each other did not work right - that's something that becomes more difficult to calculate if you've got the kind of situation where 2 things are coming close to being smooth to each other but are 5 to 10 degrees off of tangent instead of actually smooth - those kinds of grazing tangent surface intersections are more difficult to calculate.

If you have a model that has messy geometry like that, it may need to be rebuilt in order for it to be filleted more easily.

There is also another mode of the filleter that you can use if you have 2 individual surface selected instead of edges - that will generate what is called a surface/surface fillet that goes through a somewhat different process than the edge based filleter. Sometimes it is able to build some fillet surfaces in situations where the edge based one gets confused. To use this method you separate the model out into individual surfaces and build some fillet surfaces between 2 selected pieces at a time. This can require some more manual work though because it does not try to build corner patches like you would get where multiple edges come to a common point.

It's difficult to give you any very specific advice though without seeing the model that you're having problems with.

- Michael