Expressive rendering
Motivation
There is no reason to restrict the use of computers to the
simulation of physically accurate lighting. Indeed it has been
recognized in recent years that computer processing
opens fascinating new avenues for rendering images that convey
particular views, emphasis, or style. These approaches are often
referred to as "non-photorealistic rendering", although we prefer the
term "expressive rendering" to this negative definition.
A part of computer graphics can be viewed as a visual communication
tool. Such a point of view implies several goals that we target with
expressive rendering. In particular the user of an
expressive rendering tool should be able to produce the images that
corresponds to his own goals.
This involves, in particular, significant work on the notion of relevance,
which is necessarily application-dependent. The relevance should guide
the level of abstraction of the rendered scene to let the user
emphasize the most important elements of the input 3d scene. It can
also be defined from a levels-of-detail point of view: not only can we
adapt the geometry to decrease the computation time, but we can also
adapt the rendering style to meet the user's goals.
Another research direction for expressive rendering concerns rendering
styles: in many cases it should be possible to define the
constitutive elements of styles, allowing the application of a given
rendering style to different scenes, or in the long term the capture of
style elements from collections of images.
Finally, since the application of expressive rendering techniques
generally amounts to a visual simplification, or abstraction, of the
scene, particular care must be taken to make the resulting images
consistent over time, for interactive or animated imagery. This leads
to various projects targeting the temporal coherence of animated scenes.
Research projects
Abstraction, level of details
Abstraction is one of the main issues of expressive rendering. Indeed we think that the impact of an image in terms of message transmission is related to a carefull abstraction of each part of the image, depending on the targeted goal.
ARTIS is working on several project in this research field:
- Line drawing simplification
- LOD toon shader
- Relevant lines extraction
User oriented algorithms
We think that the user (artist, architect, technical designer, ...) must be able to control the rendering. It means that we have to find a compromise between automation and what could be done by hand. Our idea is to try to give as much parameters as possible to the user or to let him describe what he wants by giving examples.
ARTIS is working on several project in this research field:
- Stroke patterns generation
- Procedural style of line drawings
- A style model for stroke-based rendering
Temporal coherence
As soon as we want to animate a 3D scene rendered with primitives that are not a pixel (lines, strokes, dots, ...), we have to deal with temporal coherence.
ARTIS is working on several project in this research field:
- Dynamic Canvas
- Temporal coherence for stroke-based rendering
- Temporal coherence for watercolor-like rendering
Collaborations and applications
One of our targeted field is archaelogy.
The ARC INRIA project ARCHEOS has been a first attempt to work with archaelogists and several publications have been made during this 2 years collaboration :
Laure Heigeas, Annie Luciani, Joëlle Thollot, Nicolas Castagné - Graphicon - 2003
The ARC INRIA MIRO continues the collaboration with archaeologists adressing the problem of producing legible renderings.
Members
François Sillion
Joëlle Thollot
Cyril Soler
Matthew Kaplan
Pascal Barla
David Vanderhaeghe
Hedlena Bezerra