Shadow Algorithms Data Miner

60 2. Hard Shadows

(see Figure 2.26, where shadow polygons are generated only at the silhouette of the

object). ese silhouettes mainly correspond to the polygon edges that have dier-

ent

ˆ

N ⋅

ˆ

L positive/negative values (the view-dependent boundary case) and also to

edges that have no other shared edges (the view-independent boundary case). Such

polygon edges are the only edges that require the generation of shadow polygons,

i.e., any internal polygon edges do not need shadow-polygon generation. Such

an approach can potentially reduce the number of shadow polygons quite signi-

cantly.

As a side note, two observations about silhouettes are interestin ...