ps brush algorithm

on mousedown at (x,y):
	set brush position to (x,y)
	draw the brush
	set remaining distance to granularity distance

when mouse moves to (x,y):
	while distance from brush to (x,y) is greater than remaining distance:
		move brush towards (x,y) remaining distance
		draw the brush
		set remaining distance to granularity distance
	subtract the from remaining distance the distance from the brush to (x,y)
	move brush to (x,y)
	if the remaining distance is < 0
		draw the brush
		set remaining distance to granularity distance