This paper presents a method for accelerating the realistic
rendering in ray-tracing of forest of pine-trees
(we got a factor of 8 relatively to Rayshade in one of our examples).
As for many complex materials (hair, fur, fabric, cristals),
pine-tree needles have an effect in the tree illumination
even if their small size makes them geometrically neglectable.
The approaches for level of detail consisting in
replacing several small entities by a large single one
thus destroy important information.
One should not loose the contribution of each needle,
but at the same time one cannot afford dealing with each of
the billion of needles of the scene individually,
which would yield an untractable rendering time and a
strong aliasing.
Our approach consists in derivating reflectance functions, or
shaders, which analytically integrates the luminous contributions
(reflects, shadows, opacity) of a set of needles.
Depending of the distance, this `set' corresponds to one needle,
a cone of needles, or a whole branch.
Analytical integration is doable -with some approximations- because
a priori knowledge on the object is available (here, the shape
and distribution of the needles).
So this approach can be generalized to the various complex object
for which strong a priori knowledge exists.
L'article au format
Postscript (2.3Mo)
or
PDF (7 Mo).
The bibtex entry for this publication:
@InProceedings{MN:2000:MSE,
author = "Alexandre Meyer and Fabrice Neyret",
title = "Multiscale Shaders for the Efficient Realistic Rendering of Pine-Trees",
booktitle = "Graphics Interface",
year = "2000",
organization = "Canadian Information Processing Society",
publisher = "Canadian Human-Computer Communications Society",
month = may,
pages = "137--144",
note = "ISBN",
}
My other publications
Other publications of the team
Abstract 
Version française
More
details about this research.