Is there any SVG extension which allows density of line? I have a plotter which can lift/lower a pen; it's driven from SVG files. It'd be sweet to allow the pen to lower while the line is being drawn (as we often do with handwriting).
Oh - it's an Axidraw, from Evil Mad Scientist Labs - great device, wonderful people.
It's pretty easy to store custom instructions in plain SVG files and interpret them in with your reader. For example I have a multi-purpose laser-cutter / plotter and I use opacity for laser power, stroke weight for movement speed, green channel for number of passes, blue channel for z-axis height and red channel for lowering the pen or turning of the laser etc.
Probably you would want to do that with G-code.
I've been doing that sort of thing in: