Thank you for the plugins! I'll try them out when I get home from class.
Thank you @Ego Eram Reputo for the installation tutorial. I had issues where after I restarted paint.net the effect disappeared, and then the dll file became corrupted. I'll try redownloading it again following these steps.
And @MJW, I ... don't really understand what you're asking? Hah ... sorry, English isn't my first language, so I may not be answering what you're asking. I'd prefer if there was perspective specification as in my example since it's simply the easiest way to add perspective.
Normally when I use drawing programs (which has previously only been ms paint and occasionally sai or photoshop) I use shortcuts to make crisp perspective that's nice and precise. Using free transform allows me to create endless combination of perspective lines from a few grid brushes. Both sai and photoshop have transform modes where it's good 'ol ctrl+t is free transform, and shift is perspective transform; also, if I don't want to click and drag manually, I can add numeric values (ie, 10°, 50%, 3/8, ...) under width and height, X, and Y. Additionally sai also has perspective specification as in my example (I'm assuming you're talking about the perspective slider when you say "perspective specification").
In my example the quadrilateral represents the perspective transform rectangle. Besides clicking and dragging (which can sometimes leave wonky results) there are controls to specify how each point is moved where you enter numeric values For example, if I want to move point 1, I can type in 20% for it to move 20% closer to me, -20% to move 20% father from me, or just enter an amount in its X or Y coordinate. I find the slider to be easier to use. I would probably be fine without the slider once I learned how to ... see, the slider moves the selected image across the perspective plane by its center point, simultaneously changing the points 1XY 2XY 3XY and 4XY to keep the image in "scale". In the end I'd probably be fine without the slider. I'm just looking for something user friendly.
