Greetings everyone! Let me preface this by saying I'm not sure the Industrial Design term for this type of blend, pictured below on a game controller. The detail of interest is the blend or fillet near the sculpted area that completely fades out into the rest of the shape. I see this frequently on ergonomic designs.
These have always been a challenge for for me. The best method I have so far is to plan my surface patch structure accordingly. This means splitting the other surface edge where I imagine the fillet fading out, and creating two separate surface patches from there.
From here there is no type of fillet option I can find that will accomplish this blend satisfactorily since they seem to love to degenerate as the two surfaces fade to the same curvature.
I end up trimming back around the bend area and then using a boundary surface to accomplish the blend.
I'm generally happy with the result but it's laborious. I'm looking for a sanity check / second opinion from the gurus to see if there is a better way (maybe rethinking the patch structure?)
Attached a simplified example part (2018 format) as well as Parasolid in starting and finished state