secondary cloth simulation.pdf

computer graphics & visualization

Near-exhaustive Precomputation of Secondary Cloth Effects

represents by Pierre Suchacek

Doyub Kim Woojong Koh

Rahul Narain Kayvon Fatahalian

Adrien Treuille James F. O‘Brien

Carnegie Mellon University University of California, Berkley


<Your Topic Here> <Your Name Here>

Outline • Motivation

• Cloth Introduction

• Secondary Cloth

• Related Work

• The Secondary Motion Graph

• Definition

• Graph Exploration

• Compression

• Results


Pierre-Pascal Suchacek

source: http://www.gris.uni-tuebingen.de/



What is Cloth? • deformable

• kind of Mass-Spring System

• internal forces

• stiffness



x1

x2 x3

source: sglab.kaist.ac.kr



Only triangles?



source:

http://aras-p.info/



Now it looks better…



source:

http://aras-p.info/



Problem’s with Cloths • “Tunneling”

Continuous Collision Detection (CCD)

• The dynamics of cloths





Secondary Cloth • Problem: capture “everything”

differentiate: • Primary motion graph

represents character pose

• Secondary motion graph

represents configuration of clothing on the body

• Complexity:

secondary > primary





Related Work • Try to look more and more real measured materials

physics

run in low resolution simulation & add extra wrinkle

• Complex systems fluids

deformable objects

for speedups





Related Work • Aguiar et al. [2010]

• approximate cloth motion

• James and Fatahalian [2003]

• tabulate dynamics of deformable systems

this work:

• richer space of external cloth forces

• more complex cloth behaviors





The Secondary Motion Graph Definition:

• Primary graph: character pose pi

• Secondary graph: cloth pose ci

• Remember:

Secondary > Primary





The Secondary Motion Graph Graph Exploration:

• Graph Initialization

start at (random) initial character pose

start with inherent cloth pose

Problem:

dead-ends like c5 & c9





The Secondary Motion Graph • remove dead-ends via





The Secondary Motion Graph

red edges = actual simulated trajectories

blue edges = approximated real cloth dynamics





The Secondary Motion Graph • What if approximation is bad?

lead to implausibly & bad motions

continues repeatedly, eliminating the largest physics error





The Secondary Motion Graph

• re-insert cend (dead-end)

• simulate from cend and create subtree

repeat RemoveDeadend() and ExpandGraph()





The Secondary Motion Graph • Result:





Compression • The result leads to a hundred of GB storage

nobody can use this in a game!

have to compress

• Cloth data matrix D ∈ 𝑅3𝑣 × 𝑛

into b-dim. cloth basis B ∈ 𝑅𝑏 × 𝑛 and

trajectory coefficients C ∈ 𝑅𝑏 × 𝑛

D ≈ BC





Compression

for b = 200 cloth mesh is very similar to original model





Results • primary motion graph:

• 12 unique motion clips

• running, throwing, hopping, performing cartwheel etc.





Results • Two cloth setups:

• Robe (one-piece,

hooded rope)

• Casual (three layered)





Results • Still critical the hood of the robe

• E.g. walk -> jumping-jack -> walk





Results • red: hood up

• blue: hood down

Five sequences found





Results • Evolution of L errors of worst transition:

• Error decreases cause: • poor predictor of future error in phase • Exploration founds new part of space (fallen hood etc.)





Last words… • Cloth dynamics was shown

• Good results without hood problems was created

• 43 GB cloth motion compressed into 66 MB

• Run on laptop with over 70 fps

FAZIT: good cloth simulation results

but about 70 MB still to large as a secondary graph

Xbox 360 has only 512 MB of RAM





Thanks for your Attention!



source: wowrpc.waddellconsulting.com

secondary cloth simulation.pdf

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