To draw the shadow of the figure M on the inclined plane K (or a chimney on a roof). First find the vanishing point P of the inclined plane and draw horizontal PF to meet vertical raised from L, the luminary. Then F will be the vanishing point of the shadow. From L draw L1, L2, L3 to top of figure M, and from the base of M draw 1F, 2F, 3F to F, the vanishing point of the shadow. The intersections of these lines at 1, 2, 3 on K will determine the length and form of the shadow.
Fig. 280.
[ CLVII]
To Find the Shadow of a Projection or Balcony on a Wall
To find the shadow of the object K on the wall W, drop verticals OO till they meet the base line B·B· of the wall. Then from the point of sight S draw lines through OO, also drop verticals Dd·, Cc·, to meet these lines in d·c·; draw c·F and d·F to foot of luminary. From the points xx where these lines cut the base B raise perpendiculars xa·, xb·. From D, A, and B draw lines to the luminary L. These lines or rays intersecting the verticals raised from xx at a·b· will give the respective points of the shadow.
