In new revision I added support for miltiple sets of orthogonal vanishing points (bases). Why would you need that? Here's why:
there is a problem with this interface - say you want to draw 2 cubes in one scene, but one of them rotated 45 deg retative to other. You will need 2 assistant with exact same on-canvas position, rotation, bounds - just in one of them "camera" is rotated, so vanishing point are in different places. <- old rev
theyr controls will overlap and one of them will be unusable.