Previously, the “selected building” effect I was using was just to draw a simple wireframe box around it. But there were bugs which caused the box not to z-buffer correctly (that is, the box showed through the building). But I realised that with my procedural geometry, I’d already built all the tools I needed to draw glowing lines around the procedural shapes themselves; I’d written it for drawing region outlines that I was showing off months back.
Really, this probably also wants to have lines along the sharp corners, but that’s a little harder to work out; my procedural geometry is being worked out on a per-vertex basis, not a per-edge basis. Maybe I ought to switch to per-edge. That’d also let me cast shadows from these objects, which would be pretty cool.
But I’m not doing that until milestone 2! :)