I try to use BRepFilletAPI_MakeFillet to achieve smooth transitions between solids.
A simple example to imagine this would be two cylinders with the axis of one rotated 90° to the axis of the other and they are stuck into each other (see attached image).
So far, I've been fusing the solids to do this using BRepAlgoAPI_Fuse and then applying the fillet to the section edges of the fuse object.
There are two major drawbacks for me from this approach:
1. Since my actual use case involves multiple fuse operations that need to be done, I use BOPAlgo_CellsBuilder for this. BOPAlgo_CellsBuilder does not provide the section edges of the operation, so I have to iterate over all edges of the result shape, but I don't know exactly which of them are the section edges (and I haven't thought of a suitable criterion to derive them yet). Perhaps the edges of the individual bodies before the boolean operation could be subtracted from the resulting edges.
2. The boolean operation takes over 45 minutes and that is actually way too long for me.
My question now is if there is any other way to create the smooth transitions between the solids without a preceding boolean operation. I thought about making a compound and adding the edges that I want to be used for the fillets to that compound. So far, BRepFilletAPI_MakeFillet did not accept such a compound, but needed always a fused body. Any help would be appreciated.