.
A Framework for Multiperspective Rendering
Jingyi Yu, Leonard McMillan.
Eurographics Symposium on Rendering, Norrkoping, Sweden,
2004. [BibTeX]
A Projective Drawing System
Osama Tolba, Julie Dorsey, Leonard McMillan.
2001 ACM Symposium on Interactive 3D Graphics,
2001. [BibTeX]
Sketching with Projective 2D Strokes
Author(s): Osama Tolba, Julie Dorsey, Leonard McMillan.
Proceedings: UIST '99,
1999.
[BibTeX] 
Abstract:
Freehand sketching has long had appeal as an artistic medium
for conceptual design because of its immediacy in capturing
and communicating design intent and visual experience. We
present a sketching paradigm that supports the early stages
of design by preserving the fluidity of traditional freehand
drawings. In addition, it attempts to fill the gap between 2D
drawing programs, which have fixed views, and 3D modeling
programs that allow arbitrary views. We implement
our application as a two-dimensional drawing program that
utilizes a projective representation of points — i.e. points
that lie on the surface of a unit sphere centered at the viewpoint.
This representation facilitates the production of novel
re-projections generated from an initial perspective sketch
and gives the user the impression of being immersed in the
drawing or space. We describe a method for aligning a sketch
drawn outside the system using its vanishing points, allowing
the integration of computer sketching and freehand sketching
on paper in an iterative manner. The user interface provides
a virtual camera, projective grids to guide in the construction
of proportionate scenes, and the ability to underlay sketches
with other drawings or photographic panoramas.