The Solid Modeler's Blender Survival Guide

Quicktip 1: Extrude "In Place"



Note: I'm collecting Blender Tutorials and Links back at my home page.

I'm sort of plotting out how to do my next big Blender Tutorial, wherein I'll cover the delightfully painful topic of boolean operations, but in the meantime, I'm thinking throwing out a one-command trick every now and then would not only get certain concepts into the blog, but to lend a bit of inspiration by showing off things that are possible.

So starting with Blender's default cube, I've selected a face:



If you've read my main page of Blender Tutorials, you know that hitting the e key will cause a new square face to appear, linked to the cube as though the points had been squeezed out of the cube rather like, well, the plastic extruder on a MakerBot:



If you hit the esc key while the extruded face is still floating out there, the points will jump back to their original positions, but it's important to note: your new points have not disappeared!



You'll notice if you look carefully at these selected vertices that the gold lines which would normally fade back to black as they approached the vertices on the other side of the cube are all black. This is because the actual lines that connect these vertices to the ones on which they are now sitting directly on top are infinitely short, and thus invisible.

This could be an annoyance if you meant to cancel the extrude process-- this is certainly what you do if you want to cancel a move. But with extrude operations, the developers see that you might just want the extrude operation to leave the vertices right where they are, so that you can then do things other than simply moving the points out some distance towards or away from the face. Like hitting the s key and scaling these vertices down:



Now all five of the faces we have on this side of the cube are visible, but they're also co-planar so they may as well not exist for printing purposes. However, we have now subdivided the mesh, and only on this face. One benefit to this is that we can now extrude substructures that rise up from this face at right angles:



All of the shapes in the first picture were created by only using this "extrude in place" technique on different primitives. Little bits of topological slight-of-hand like this are both why Blender can be so frustrating, and why it is so powerful. Because it is mesh-aware, one is a lot less likely to have mesh operations fail for reasons that can't be found out by squinting at the mesh long enough, but on the other hand, you end up squinting at meshes a LOT.

Last note: the dodecahedron in the top image has had one of its faces rotated in place before extruding. This was carried out by hitting the r key after hitting the e key with that face selected. The extrude operation locks the reference frame locally, so the rotate operation rotated the faces in the plane of their normal. Once that was done, the instructions for creating that pentagonal protuberance were identical to the ones for the others. Back to the Solid Modeler's Blender Survival Guide