Art-based Rendering with Continuous Levels of Detail
Author(s): Lee Markosian, Barbara J. Meier, Michael A. Kowalski, Loring S. Holden, J.D. Northrup, John F. Hughes.
Proceedings: 1st International Symposium on Non-Photorealistic Animation and Rendering (NPAR'00), pp. 59--66, Annecy, France, June 05 - 07,
2000.
[BibTeX] 
Abstract:
In previous work [6], we presented an algorithm for rendering virtual
scenes using art-based styles. We demonstrated the ability to
render fur, grass, and trees in a stylized manner that evoked the
complexity of these textures without representing all their components
explicitly. We achieved this with stroke-based procedural textures
that generated detail elements, or graftals, just as needed.
Our implementation had several drawbacks. First, each new graftal
texture required a procedural implementation that included writing
code. Also, graftals were regenerated in each frame in a way
that led to excessive introduction and elimination of graftals even
for small changes in camera parameters. Lastly, our system provided
no way to continuously vary the properties of graftals, including
color, size, or stroke width. Such an ability could be used
to achieve better frame-to-frame coherence, or more generally to
animate graftals.
In this paper, we present a new framework for graftal textures that
addresses these issues. Our new framework allows all major decisions
about graftal look and behavior to be specified in a text file
that can be edited by a designer. We have achieved greater frameto-
frame coherence by using graftals that remain in fixed positions
on the model surface. The look and behavior of graftals as they
appear or disappear can now be animated to create smooth transitions.
Finally, we introduce the concept of tufts which manage the
multiresolution behavior of graftals according to the specifications
of the scene designer.