Computer Graphics Research and Advances

Advances in Computer Graphicsin the context of the ASCI project

Peter Schröder

Mathieu Desbrun Fehmi Cirak Igor GuskovAndrei Khodakovsky Adi Levin Zoe Wood

Nathan Litke Steven Schkolne Mark MeyerJianhui Zhang Kiril Vidimce

Multires Modeling Group, Caltech

Modeling: Subdivision Surfaces (I)

Why subdivision surfaces: powerful tool for smooth surface

representation

no patches, any topology, intuitive

smooth surface as limit of subdivisions

strong mathematical bases

shape functions, wavelet theory

Simple example:

Level 0 Level 1 Level 2 Level 5

Modeling: Subdivision Surfaces (II)

Current general effort: development of a subdivision library for 2-manifolds

provide solid and generic development platform

teaching tool, technology transfer to industry

fine and crucial studies for improved control

boundaries, corners, creases, curvature, ...

development of various modules

quadrature and stiffness for physics, hierarchical PDE solver, Rivara/PM mesh adaptation...

Modeling: Subdivision Surfaces (III)

Research for extended editing abilities fine level feature editing

adds flexibility

allows hierarchical editing

of additional features

surface trimming

cutting holes

in subdivision surfaces

Applying a standard hierarchical editing modification to the coarse surface carries along any features at finer scales as one

would expect.

Design study for a bicycle helmet (by Khrysaundt Koenig),featuring both holes and fine features.

Simulation (I)

Subdivision surfaces for physical modeling basis and shape functions are one and the same!

unified formalism for modeling and computation

efficient computational framework

mesh adaptation, multilevel preconditioning, ...

accurate on complex mechanical models

allows non linear analysis, contact, ...

Results of a thin shell simulation through time

Simulation (II)

Fast and robust solvers for CG and VR real-time computations needed for VR applications

unconditionnally robust, guaranteed fast computations

implicit integration using prediction/correction for efficiency

adaptive local resolution to cut down computation time

robust extended FD operators on irregular sampling

Piece of cloth manipulated in real-timeLiver manipulated in real-time, with

different levels of resolutions in false colors

Dealing with irregular sampling (I)

Multiresolution signal processing for meshes mesh hierarchy generated by successive

simplifications

arbitrary, irregular mesh as an input

Signal processing tools extended using this hierarchy

editing, smoothing, enhancement, ...

Extends wavelets to irregular sampling

A mannequin head can either smoothed out, or inversely, enhanced. Example of editing of a complex initial mesh

Dealing with irregular sampling (II)

Definition of robust differential discrete operators Finite-Difference methods valid only for regular

sampling

meshes unfortunately often highly irregular

in multiresolution, different sampling coexists

construction of discrete operators (FD-like) for:

meshes: mean curvature, gaussian curvature, ...

irregular sampling: laplacian, volume expansion, ...

To fill To fill

MY OTHER PIX (smoothing)

Semi-regular meshing (I)

Surface extraction from data various sources of data

CT/MRI industrial volume data, 3d scanner, ...

desired output: semi-regular mesh

classic algorithms give dense non-smooth meshes

general idea: multi-grid on volume & surface

iteratively solve as a varational problem

Residual distance midway through minimization

Penultimate residual distance after minimization

Final mesh after minimization

Semi-regular meshing (II)

Remeshing of arbitrary meshes initial meshes are often unfit for solvers

arbitrary connectivity, irregular density, ...

remeshing through robust parameterization

hierarchical analysis, smoothing of parametrization

resulting meshes adequate for FEM computations

Interaction in immersive environments

A radically different look at interaction the simpler the tools, the better

blah?

experiments on art creation

different crowd, no prior technological knowledge

freedom of expression

paradigm reusable in data manipulation

defining trajectories of shapes intuitively as initial conditions for instance.

STEVEN’S PIX

Building better immersive environments

Towards adequate and usable VR systems each virtual environment has

its pros and cons responsive workbench (rwb),

immersadesk, cave, ...

semi-immersive environment better for data exploration both rwb and immersadesk are

adequate

creation of a portable dual-display VR environment two orientable panels for optimal view volume portable,cheap: next generation of desk computers?

Mock-up of the portable dual-screen workbench