So that would mean if you created a million new sprites every tick, uid's would overflow after a bit longer than 4 years of continuously running at 60fps.
Construct2 also does object recycling so it doesn't cause javascipt's garbage collector to have to work as much.
I had another go at it here:
https://dl.dropboxusercontent.com/u/542 ... htTri.capx
It take any polygon with a clockwise vertex winding, without self intersections and converts it to triangles. One issue is there are seams between the triangles which should be correctable by scaling the triangles up sightly from their centers, but I've been having trouble getting perfect results.
The simplest way would be to just draw a polygon with the canvas, but as I mentioned before, it will have a performance hit with webgl on. With the paster object you'll need to triangulate the polygon, but since it draws quads it can be more efficient if merge adjacent triangles to make it mostly quads.
Both canvas and paster handle blending modes fine since they are just images. Also they only have bounding box collisions.