Hey, good to see you here, welcome 🙂

If you're using mask, it's always best to use PNGs. Because mask only masks off an exact colour, the compression artefacts that JPG introduces into the image makes the masking miss a lot of pixels you would expect it to get.

The other thing is that there is no transparency option at all in the polargraph controller - a transparency channel, or "colour" has no special meaning to the controller, so it's brightness is the only thing that is looked at. It might be that the transparent colour is hidden in your image editor, but it is taken literally by the controller.

The best thing to do in this case is forget the transparent background, and make it some solid colour (you're probably already doing that), and mask that colour. You should see the render preview has hidden the background. When you choose "render pixel" and make sure "Lift pen over masked pixels" then it will lift the pen over the pixels that are masked. The annoying thing is that it will still "draw" the pixels (so it is slow), but the pen will not make a mark because it is lifted.

I'm not sure I know what you mean by the "no lines in the masked area" though - do you want the masked area to have lines through, or to be completely empty?

sn