Since the parallella doesn't have a gpu it leaves it to software.
I looked into how hardware does it presently and it seems to be down to the technique described in Triangle Scan Conversion using 2D Homogeneous Coordinates so that's what I looked at. I got a basic 2d half-space triangle rasteriser going quickly but wanted a quicker solution for something more capable (and I couldn't find some of the references on the net) so did a hunt and came across the ATTILA project which has all the bits needed. I've only done a cursory scan for what i was interested in right now but I expect i'll becoming quite acquainted with it should i continue working on this for any time.
I extracted some of the low-level bits from it, set up some vertex handling and matrix code and ended up with a very basic solid-colour rasteriser for a 'hello cube' demo:
Definitely not going to break any speed records but it does run at full-frame rate on this pc even if it's only flat shaded. (it's java+javafx on a kaveri pc).
Getting this stuff working on the epiphany will be ... well interesting I guess.
Ahah, I just sussed out the parameter interpolation, an important bit I needed before looking at epiphany code.