The Phi Quadrilateral
The Phi Quadrilateral. Phi Quadrilateral a b x y c d Figure 1: A Phi Quadrilateral that I coded in SVG. I believe that these are used for perspective. The first quadrilateral will have its base line-segment at the bottom of the canvas, in the foreground. A second quadrilateral - scaled to 0.618033988... the size of the first, will have its base equal in magnitude to the top line segment of the original quadrilateral. This second quadrilateral has its base at the top line segment of the first quadrilateral. ...