Graphics Reference
In-Depth Information
(
c
Figure 8.80
Rendered images under different simulated lighting conditions.
Arno Zinke, GfaR
mbH.) (See Color Plate XX.)
paper described earlier (see
Figure 8.50
)
. Separation into direct and indirect il-
lumination is essentially the same as the splitting of scattering into single and
multiple components in hair. The single scattering is, in essence, the effect of
direct lighting. However, the separation would have to be performed in terms of
the hair volume—the direct reflectance from hair fibers has higher frequency than
the checkerboard light pattern.
Another interesting connection is the link between hair color and hair geome-
try. As has been noted several times, the local arrangement of hair fibers substan-
tially affects the appearance of color. It seems reasonable that a good color model
could assist in the reconstruction of hair geometry. Because the optical features
of hair, particularly highlights, are closely related to the orientation and curvature
of the hair, exploiting the relationship between geometry and color could increase
the accuracy of measurements and the realism of the rendered results.
8.6.3 Further Directions
As previously mentioned, “hair” is commonly visualized as a volume, mainly
concentrating on large-scale structures. However the methods introduced in this
section concentrate on the small-scale structures, and this has successfully led to a
higher level of realism. From a practical standpoint, it can be said that these tech-
niques are still in an early stage. But current demand for realistic hair rendering is
likely to push this work into a more practical stage in the near future. Even now,
the potential of this work is clear. For example, very little was known about the
characteristics of the local structure of hair fibers until these recent publications.
The data that these methods provide can be used to revise existing methods for
hair modeling. Furthermore, the importance of the link between geometry and
color is interesting from a theoretical standpoint. The importance of local micro-
