Hi hl, hmmm well something like a scripted export to OBJ format with "triangles only" to a specific filename, then using Max's _ImportOBJ to read it back in again could work.

But I can probably cook up one for you that extracts 3 lines and makes a planar surface out of them.

What rule do you want for which diagonal to choose, should it be the shortest one?

I can take a look at doing that tomorrow.

- Michael