I-COLLIDE: An Interactive and Exact Collision Detection System
for Large-Scale Environments
Jonathan D. Cohen Ming C. Lin Dinesh Mano cha MadhavK.Ponamgi
Department of Computer Science
University of North Carolina
Chap el Hill, NC 27599-3175
fcohenj,lin,mano cha,p [email protected]
ABSTRACT: or grasp ed. Such actions require accurate collision detec-
We present an exact and interactive collision detection tion. However, there maybehundreds, even thousands
system, I-COLLIDE, for large-scale environments. Such of ob jects in the virtual world, so a brute-force approach
environments are characterized by the numb er of ob jects that tests all p ossible pairs for collision s is not acceptable.
undergoing rigid motion and the complexity of the mo d- Eciency is critical in a virtual environment, otherwise
els. The algorithm do es not assume the ob jects' motions its interactive nature is lost [24]. A fast and interactive
can b e expressed as a closed form function of time. The collision detection algorithm is a fundamental comp onent
collision detection system is general and can b e easily in- of a complex virtual environment.
terfaced with a variety of application s. The algorithm
The ob jective of collision detection is to rep ort all geo-
uses a two-level approach based on pruning multiple-
metric contacts b etween ob jects. If we know the p ositions
ob ject pairs using b ounding b oxes and p erforming exact
and orientations of the ob jects in advance, we can solve
collision detection b etween selected pairs of p olyhedral
collision detection as a function of time. However, this
mo dels. We demonstrate the p erformance of the system
is not the case in virtual environments or other interac-
in walkthrough and simulation environments consisting
tive applications. In fact, in a walkthrough environment,
of a large numberofmoving ob jects. In particular, the
we usually do not haveany information regarding the
system takes less than 1=20 of a second to determine all
maximum velo city or acceleration, b ecause the user may
the collisio ns and contacts in an environment consisting
move with abrupt changes in direction and sp eed. Due to
of more than a 1000 moving p olytop es, each consisting of
these unconstrained variables, collision detection is cur-
more than 50 faces on an HP-9000/750.
rently considered to b e one of the ma jor b ottlenecks in
building interactive simulated environments [20].
1 INTRODUCTION
Main Contribution: We present a collision de-
Collision detection is a fundamental problem in computer
tection algorithm and system for interactive and exact
animation, physically -based mo deling, computer simu-
collision detection in complex environments. In contrast
lated environments and rob otics. In these applications ,
to the previous work, we show that accurate, interac-
an ob ject's motion is constrained by collisio ns with other
tive p erformance can b e attained in most environments if
ob jects and by other dynamic constraints. The prob-
we use coherence to sp eed up pairwise interference tests
lem has b een well studied in the literature. However, no
and to reduce the actual numb er of these tests we p er-
2
go o d general collision detection algorithms and systems
form. We are able to successfully trim the O n p os-
are known for interactive large-scale environments.
sible interactions of n simultaneousl y moving ob jects to
A large-scale virtual environment, likeawalkthrough,
O n + m where m is the numb er of ob jects very close
creates a computer-generated world, lled wi