Install

Edit > Preferences > Get Extensions > the small arrow at the top right > Install from Disk > select regosplit-x.y.z.zip. The panel appears in the 3D Viewport sidebar (press N) under RegoSplit. RegoSplit is also in the right-click menu of the 3D Viewport.

Quick start: the numbered list at the top of the panel

1. Set up the file. Press Project Setup for 3D Printing: 1 Blender unit becomes 1 mm, the display switches to millimeters and the viewport clipping is fixed so small parts stay visible. If the panel says your model is over a meter across, type the real height in Print size (mm) and press Set Print Size: every setting below depends on this being right. Several selected pieces are scaled together and stay assembled.
2. Check the mesh. Press Check Mesh. It names what it finds. Quick Fix welds, closes holes and removes junk without touching the shape; Rebuild Solid rebuilds a self-intersecting sculpt into one watertight surface, keeping your materials and leaving a hidden _backup copy.
3. Check overhangs. Turn on Overhang Preview and keep sculpting. Green is fine, yellow is borderline, red needs support, magenta floats in mid-air. Nothing is written to your materials.
4. Split the colors. Too many colors? Reduce Colors first. Then Separate: each color becomes a solid inlay with a matching recess. If a part wraps right around the model the panel turns red: press Split Ring in Two and it opens into segments that close around it.
5. Cut it down. Slice by Height for even slabs, or add cut planes and place them by hand.
6. Choose the joint. Dowel, Fused pin or Magnets. Pins come as cylinder, cone, square or triangle; magnets as 3 x 2 up to 10 x 3 mm, or the size you type. Then press Split. Changed your mind? Adjust and press it again, or Back to Draft to start over. A Split that is refused keeps your previous parts.
7. Print. Check Bed Fit > Arrange on Bed > Export All Parts. Next to the files you get RegoSplit_assembly_plan.txt: what to print, how many times, how many magnets to buy, and which cut joins which parts. In Dowel mode the dowel is one object to print several times; its name says how many (..._dowel_print_x4).

Getting the fit right, once

Open Fit: Coupon and Saved Profiles. Press Calibration Coupon, print the bar and the pin, and find the socket the pin slides into snugly: the clearance is engraved beside each hole. Press the button with that number, then press + to save it under a name such as "A1 PLA". From then on one click on the profile sets the clearance, in any file. Roughly 0.20 mm on a well-tuned machine, 0.35 to 0.50 mm on most.

Magnets

Every joint site gets one pocket on each face, so it takes two magnets; the assembly plan gives the total. Glue the magnets into one part first. Then put a loose magnet onto each glued one, let it snap, and glue it into the other part from there: that way every pair attracts instead of repelling. Measure your magnets, because cheap ones are often 0.1 mm off; Magnet Clearance is there for that.

If something looks wrong

• No pins appeared. The model is probably far larger or smaller than a real print. Check step 1.
• Separate by Color made nothing. The message says why. On a very dense mesh, rebuild with a bigger voxel (0.5 to 0.8 mm) and try again.
• Blender looks frozen. The confirmation dialog warned you it would. Let it finish: it is working, not crashed.
• The rebuild damaged a thin part. The panel says so and by how much. Ctrl+Z, set a smaller Voxel (mm), rebuild again.
• Export asks you to save the file first. An unsaved file has no folder for the default //regosplit_out/ to point at. Save the .blend, or pick an export folder in Step 7 options.

Video tutorials

Short tutorials, one per workflow, are recorded and will be linked on the product page as each one goes up. Everything they show is written above.