300dpi at 16 x 20 inches is 4800 x 6000 pixels in size.
That's a really large image! ArtRage doesn't have as good memory management as Photoshop. Additionally we need to store much more information per layer than Photoshop needs to - as well as colour, we have paint depth, wetness information, and reflectivity and shininess.
I'm looking at putting better memory management into ArtRage (but lets face it, that's whole bunches of no fun to be working on when I could be doing better tools!)
We're looking at options for interoperability with other applications as well, so plugin support might make it to a future release.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"