January 28 – Organizational meeting

February 4 – Similarity-Based Surface Editing (Steve Zelinka)

We present several powerful new techniques for similarity-based modelling
of surfaces using geodesic fans, a new framework for local comparison of
surfaces. Similarity-based surface modelling provides fast, intelligent
surface manipulation by simultaneously applying a modification to all
similar areas of the surface. Our system supports several different
similarity-guided operations, including surface painting, deformation and
smoothing. In addition, varying the similarity measure to encompass
geometry, textures, or other signals provides further control over
surface editing.

Geodesic fans are neighbourhoods which are uniformly sampled in the
geodesic polar coordinates of a point on a surface, thus resembling
a fan of geodesics emanating from the point. As they may be discretely
rotated about their center simply by reordering their spokes, and
provide a structurally equivalent definition of neighbourhoods everywhere
on a surface, geodesic fans offer fast approximate alignment and
comparison operations. They are thus well-suited to extending standard
techniques for modelling by example to surfaces.

February 11 – Animating Suspended Particle Explosions (Patrick Lacz)

The presentation will focus on the simplifications made to physical
models that the authors used to simplify and speed up the required
computation. We will also compare the results between this paper
and previous academic work in animating explosions.

from the SIGGRAPH 2003 paper by Feldman, O'Brien, and Arikan

This paper describes a method for animating suspended particle
explosions. Rather than modeling the numerically troublesome,
and largely invisible blast wave, the method uses
a relatively stable incompressible fluid model to account for
the motion of air and hot gases. The fluid�s divergence field
is adjusted directly to account for detonations and the generation
and expansion of gaseous combustion products. Particles
immersed in the fluid track the motion of particulate
fuel and soot as they are advected by the fluid. Combustion
is modeled using a simple but effective process governed by
the particle and fluid systems. The method has enough flexibility
to also approximate sprays of burning liquids. This
paper includes several demonstrative examples showing air
bursts, explosions near obstacles, confined explosions, and
burning sprays. Because the method is based on components
that allow large time integration steps, it only requires a few
seconds of computation per frame for the examples shown.

February 18 – Globally Smooth Parameterization (Jingyi Jin)

As the name suggests, the goal of this paper is to find a parametrization
method for arbitrary genus surface meshes which computes a globally
smooth parametrization with low distortion. In this presentation, I will
focus on describing the core algorithm, comparing the method with previous
techniques, and presenting the results and its assessments.

from the SIGGRAPH 2003 paper by Khodakovsky, Litke and Schr�der

Good parameterizations are of central importance in many digital geometry
processing tasks. Typically the behavior of such processing algorithms is
related to the smoothness of the parameterization and how much distortion
it contains, i.e., how rapidly the derivatives of the parameterization
change. Since a parameterization maps a bounded region of the plane to the
surface, a parameterization for a surface which is not homeomorphic to a
disc must be made up of multiple pieces. We present a novel
parameterization algorithm for arbitrary topology surface meshes which
computes a globally smooth parameterization with low distortion. We
optimize the patch layout subject to criteria such as shape quality and
parametric distortion, which are used to steer a mesh simplification
approach for base complex construction. Global smoothness is achieved
through simultaneous relaxation over all patches, with suitable transition
functions between patches incorporated into the relaxation procedure. We
demonstrate the quality of our parameterizations through numerical
evaluation of distortion measures; the rate distortion behavior of
semi-regular remeshes produced with these parameterizations; and a
comparison with globally smooth subdivision methods. The numerical
algorithms required to compute the parameterizations are robust and run on
the order of minutes even for large meshes.

February 25 – Generalizaing Barycentric Coordinates (Anil Hirani)

March 3 – Spherical Parameterization (Jeff Chang)

March 10 –

1. Flow on Surfaces (Don Schmidt)

1. Bounded-distortion Piecewise Mesh Parameterization (Nate Carr)

from the Vis 2003 paper by Sorkine, Cohen-Or, Goldenthal, Lischinski

Many computer graphics operations, such as texture mapping, 3D
painting, remeshing, mesh compression, and digital geometry processing,
require finding a low-distortion parameterization for irregular
connectivity triangulations of arbitrary genus 2-manifolds.
This paper presents a simple and fast method for computing
parameterizations
with strictly bounded distortion. The new method
operates by flattening the mesh onto a region of the 2D plane. To
comply with the distortion bound, the mesh is automatically cut
and partitioned on-the-fly. The method guarantees avoiding global
and local self-intersections, while attempting to minimize the total
length of the introduced seams.
To our knowledge, this is the first method to compute the mesh
partitioning and the parameterization simultaneously and entirely
automatically, while providing guaranteed distortion bounds. Our
results on a variety of objects demonstrate that the method is fast
enough to work with large complex irregular meshes in interactive

March 17 – Untangling Cloth (Jerry Talton)

March 24 – Spring Break

March 31 – Perlin's Kaleidoscope (Tony Kaap)

April 7 – SIGGRAPH TBD (Jared Hoberock/Mike Flavin)

April 14 – MSFT content (Jesse Hall) + SIGGRAPH TBD (Akash Kushal)

April 21 – SIGGRAPH TBD (Wen Su)

April 28 – SIGGRAPH TBD (Hui Fang/Scott Kircher)

May 5 – SIGGRAPH TBD (Lin Shi)