On Fri, 10 Jan 2003 Jim.Gettys at hp.com wrote:

> As I understand it, OpenGL will tend to have "interesting" artifacts
> at the boundaries between triangles: these tend not to be noticed
> in 3D applications due to the rapid repaint, but are often highly
> objectionable in 2D apps.

I don't think so. OpenGL has well-defined rasterization semantics.
It ensures that there is neither overdraw (leading to visible
double-blending) nor gaps between adjacent primitives.

You might be referring to certain sub-pixel-sized triangles (multiple
triangles covering a single pixel). Here, it depends on the sub-pixel
rendering accuracy of the accelerator.  But this is irrelevant if we talk 
compositing which certainly uses primitives larger than a single pixel.

-- Bert