Rendering Issues - Computer Animation: Algorithms and Techniques - page 400

FIGURE A.12
Scene with drop shadows indicating relative depth and, therefore, relative height and size.
FIGURE A.13
Computing the drop shadow by perspective projection.
(see Figures A.14 and A.15 ) . The drop shadow has the correct silhouette for a light source directly
overhead but without the computational expense of the perspective projection method.
The drop shadow can be effective even if it is only an approximation of the real shadow that would
be produced by a light source in the environment. The height of the object can be effectively indicated
by merely controlling the relative size and softness of a drop shadow, which only suggests the shape of
the object that casts it. For simple drop shadows, circles can be used, as in Figure A.16 .