Resolving Surface Collisions through

Intersection Contour Minimization

Pascal Volino

Nadia Magnenat-Thalmann

MIRALab, University of Geneva

SIGGRAPH 2006

Abstract

Advanced methods are need for CD To recovery intersecting surfaces

Not rely on intersection regions More broader application Much simpler to implement

Outline

Introduction Related Work Description of the Method Results Conclusions

Introduction

Introduction

Early CD for cloth are restricted for cloth and volumes

Methods for ensuring adequate constrains are complex

Related Work

Related Work

Not only prevent but also repair the intersections

Common approach is to identify the “collision regions” by Volino et al.[1995] Retain a constant orientation with detection Impractical to implement

Related Work

Simpler approaches preventing surface intersections to occur or sprea

d Baraff et al [2003] use “flypapering” Bridson et al [2003] preserve wrinkle patterns Bridson et al [2002] the most comprehensive way

Related Work

A major contribution by Baraff et al [2003] Global Intersection Analysis method Track intersections by identifying closed contour Establish orientation correspondence Apply collision response method

Major restriction Necessity of closed

intersection contour

Related Work

A major contribution by Baraff et al [2003] Global Intersection Analysis method Track intersections by identifying closed contour Establish orientation correspondence Apply collision response method

Major restriction Necessity of closed

intersection contour

Goal

To overcome these limitations Intersection region Non-consist constrains Impractical to implement

Minimizing the length of the intersections contour Rather than spending time to identifying colliding

surface regions

Description of the Method

Minimizing Edge-Polygon Intersections

Integration with Collision response

The local and the Global Scheme

Description of the Method Resolution scheme

Define a collision scheme that induce a relative displacement

So as to reduce the

length of the

intersection contour disappearance

of the surface

intersection

Minimizing Edge-Polygon Intersections

Minimizing Edge-Polygon Intersections

The local and the Global Scheme

Sometimes not efficient if the contour is already quite

straight or the actions are the

largest on the region

Results

Some Test ExamplesPerformance and Limitations

Results

Integrated in a cloth simulation engine Based on particle systems for accurate

representation Broad-phase CD using AABB hierarchies Collisions are detected through edge-polygon

intersections

Some Test Examples

Untangling Cloth Surfaces Local scheme works poorly in this context Between 0.4 and 0.2 sec per iteration

Some Test Examples

Robustness Test Randomly ignoring 50% of all collisions detected Local scheme is fairly efficient in this context

Some Test Examples

The Ribbon Simulation 80000 polygons of

the ribbon, took

roughly 3 to 30 sec

per iteration Shear deformations

often break the

simulation

Some Test Examples

Garment Simulation Several layers of cloth Not always accurate

Performance and Limitations

The number of edge-polygon intersections remains very low Compared to the number of regular collisions

between mesh elements Resolve intersections progressively along the

simulation is more efficient

Performance and Limitations

In few configurations, the algorithm converges to a local minimum

Combined with intersection region identify

Conclusions

Conclusions

The method is general and not suffer from the limitations of existing method

Simple to implement The local scheme only relies on a simple

geometrical computation The global scheme efficiently solve very large

surface intersections easily be combined with most usual

approaches for CD

Question?