Or to get really good at creating polygon coordinates in my head.

My new fan duct is an improvement over the old one, which was an improvement over a bare fan with a dab of packing tape. (I made something that directs the air where I want it in a nearly straight line, rather than just making a box with holes at the other end and relying on pressure to force some air out.)

But it’s still lousy because I can’t do a good job of specifying the internal duct lines. I can see them in my mind, I could even probably make them out of cardboard (not at this scale) but I can’t figure out how to specify them in Openscad. The basic shapes are fine — I just extrude some hollow rectangles in the direction I want them to go — but the details of how they intersect are lousy, and I can’t fix it without piles and piles of math.

Maybe I could import the finished shape into Meshlab and tell it “cut out these faces and replace it with a face here“, but Meshlab always scares the blazes out of me. I can seldom predict what it will do, and half the time I end up with something  so nonmanifold you have to laugh.

I know Freecad has an openscad mode, but I’m not sure it will let me do the kind of multimodal design that I want (and I haven’t been able to climb the learning curve to find out). Should I just dive in? Any other suggestions?