Rays of light travel in straight lines. From any spot, the middle ray, the “perpendicular to source,” would meet the earth and pass through its center. At the point directly under the source we establish the point DL, meaning “direction of light.” S will mean “source” at the top of the perpendicular, from the farthest limit of the shadow to DL, then up to the source and back to the shadow, forms a triangle. The third corner of the triangle will be called “AT”, meaning “angle of light.” DL may be the vanishing point of the shadow or the base from which it proceeds outward. |