Painting surface characteristics
Poulin and Alain
Proc. Sixth Eurographics Workshop on Rendering, June 1995
Surface illumination proceeds according to the strict rules
of the reflection model, the light characteristics and the geometry of
the scene. To get a given illumination effect on a surface in a fixed geometry,
a user must determine the surface characteristics that will produce this
effect. This process is part of what is called inverse illumination. In
most current modeling systems, the user must rely only on intuition to
perform this inverse illumination, which can lead to many modeling/rendering
cycles to achieve a satisfactory result.
In this paper, we are concerned with the case where lighting effects
are not merely a consequence of the geometry, but rather part of the design.
We therefore concentrate our efforts on controlling the surface characteristics
and present a tool which can reduce considerably the problem of inverse
illumination by using a "painting" paradigm. An interactive system is provided
where the user simply applies color points on a surface. The system then
attempts in near real time to find the "best values" for the surface characteristics
such that the points will retain their assigned color in the final rendering.
Depending on the number of constraints (color points) given by the user,
the solution is presented as a non-linear constrained optimization and
a constrained weighted least-square fitting. We apply our solution to a
simple illumination model using ambient, diffuse and specular components
to illustrate our approach.
author = "Pierre Poulin and Alain Fournier",
title = "Painting Surface Characteristics",
booktitle = "Eurographics Workshop on Rendering 1995",
year = "1995",
organization = "Eurographics",
month = jun,
pages = "160--169",