Create a perspective view looking through the centre of a rectangular frame.

Input parameters:

1. Fr → Framing rectangle of the view.
2. Ll → Lens length (in millimetres) for a canonical 36mm sensor.
   •  14 → 14mm Ultra-wide
   •  24 → 24mm Wide
   •  35 → 35mm Moderate Wide
   •  50 → 50mm Normal
   •  85 → 85mm Portrait
   • 100 → 100mm Macro
   • 135 → 135mm Telephoto
   • 200 → 200mm Long Telephoto
   • 500 → 500mm Near Isometric

Output parameters:

1. Vw → View looking at the frame.
2. An → The resulting view angle.