Trim/Extend to Corner

Yesterday I completed Trim/Extend to Corner to the point that it functionally does all I want it to do. If you've used Revit, it's TR.

I expected the geometry to be the difficult part. Before writing any of it, though, I went back to the Revit documentation to pin down what it actually does at a wall join. That turned out to be less obvious than I remembered.

There isn't one join tool. There are five separate things people call joining: the automatic join when a wall end lands on another wall, the Wall Joins tool, Trim/Extend, Split, and Join Geometry, which is something else altogether. Underneath all of them, Revit resolves a join per layer, by Function priority, with one special rule for the core.

That settled how Aplo does it. A wall is joined layer by layer: each layer is mitred onto its match in the other wall, so the corner closes all the way through, not just on the outside faces.

The bigger decision was to make it the same code for everything. An Aplo wall, a group of layers drawn with another extension, a loose line — to the tool, a line is just a wall with no thickness. So a line against a layered wall works the same way as two lines. Lines are the everyday case. Walls are why I built it.

Using it is two clicks, each on the side you want to keep. There's no dialogue asking which corner you meant: the side you click is the side that stays. The Tool Page shows every case it handles, before and after.

And when there's no corner — two parallel lines, or two lines in one line — it leaves the model alone and says why in the status bar, rather than doing something you didn't ask for.

The useful result isn't only a wall-join tool. It's one trimming operation that works from a loose line up to a layered wall. The next question was what to do when only one of the two should move.