Turning an alpha into IMM can be done quite a few ways but the easiest is the Make Alpha 3d button in the alpha palette which will give you geo you can turn into an IMM brush immediately, using the brush/create insert mesh/new (or append to an existing IMM). But like you said overlap may be a thing and if you want absolute precision and mirror and weld isn't working for you try experimenting with creating 3d geo out of your alphas, like I said there's a bunch of ways to do that including morph targets and morph difference meshes and whatnot but creating a VDM is probably the fastest high quality way of doing that, so check out youtube about VDM creation from alphas, the videos explaining this take about 6 times longer to actually just do it once you undertsand how it's done hah, it's very fast to turn an alpha into high quality geo to use as an IMM these days. So click to draw in when the red dots converge at the center, then hold shift and scale up, bingo it's in the center always. Turn the alpha into a IMM then you can use the move gizmo on it after drawing it out, if you send the gizmo to center of world space on your first subtool then click the send object to center of gizmo (mesh to axis) button on your alpha turned IMM, your IMM will appear at object center of the first subtool as long as the target subtool center is at the world space center and your gizmo is lined up on that you'll be good to go, then you can reset the orientation of the gizmo to adjust the IMM precisely (in symmetry mode) holding shift while dragging it's movement handles and it will always be based in absolute constraint to axis.Īnd maybe a little less advanced is to just hold shift after clicking the middle of your mesh you're drawing your alpha onto (in symmetry mode) that will constrain it directly to center.