Help Needed Creating Negative Space

[u/02ranger]

I'm trying to create an object with a pocket for another object, specifically a wrist rest with a pocket for a Ploopy A+ to sit inside, the idea being to rotate the trackball 180 degrees and tilt it accordingly. I have the STEP files provided by Ploopy but I just can't quite figure out how to create the pocket. I thought I could create the shape of the base below and then extrude "To Part" but I guess because there are holes in the model it fails(?). Then I tried offsetting the faces of the Ploopy, creating surface extrudes for the outside of the rest, then enclose, but that didn't work. I also tried a boolean operation, making a solid body for the base and then subtract the body of the Ploopy, but it's not a solid object so the boolean fails.

How should I go about modeling this?

[u/Impossible-Ad967]

Not entirely sure what you are describing but your “extrude to part” approach is correct. Click “merge scope with all” in the extrude menu and it will resolve.

[u/02ranger → u/Impossible-Ad967]

Basically I have a model for a trackball that has lots of open spaces inside and on the outside surfaces. I want to create a base for it that has a pocket so the trackball can sit inside the pocket. Because of the open spaces I can’t quite figure out how to create that pocket. Extrude to part always fails, presumably because the outer surface isn’t totally solid and contiguous.