I am attempting to draw a plane defined by three points.
What I've done is I started out with a vertical rectangle in perspective, and I've drawn three points at varying distances from the points on the vertical rectangle, along the lines connecting the corners to the vanishing point.
Now, however, I am trying to find where the fourth point on the plane, defined by these last three points, should go. According to the picture, the fourth point should be on the line labeled with the question mark--but for the life of me I can't figure out where. Is there a general technique in drawing to find the point?