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[ VRST2004 ] [ TVCG2004 ] [ Sewing Garment Process ]

[ Wingo WONG PhD Thesis (Dec 2004) ]




A Randomized Marking Scheme for Continuous Collision Detection in Simulation of Deformable Surfaces

W.S.-K. Wong and G. Baciu,

VRCIA 2006, to appear

Wingo Sai-Keung WONG



[ Movie (mov) 9MB ]

Continuous collision detection techniques are applied extensively in the simulation of deformable surfaces, in particular for cloth simulation.  Accurate contact information can be computed by using these techniques.  Traditionally, for meshed surfaces, after collecting the triangle pairs that are potentially interacting, the feature pairs of these triangles are directly sent for the computation of collision information. Many feature pairs end up being processed repeatedly because a feature may be shared by more than one triangle.  In this paper, we propose a randomized marking scheme to mark triangles and embed a \emph{feature filtering layer} (FFL) in the pipeline of continuous collision detection.  The purpose of the FFL is to extract potentially interacting feature pairs according to the marking of the triangles. By applying the FFL each interacting feature pair is processed exactly one time for the computation of collision information.  On average, the number of potentially interacting feature pairs reduces significantly after filtering.  We have integrated the FFL in a cloth simulation system.  Interactive rates can be achieved for complex draping simulation.



ÓACM, (2006). This is the author’s version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in PUBLICATION, {} http://doi.acm.org/



GPU-based Intrinsic Collision Detection for Deformable Surfaces

W.S.-K. Wong and G. Baciu,

Computer Animation and Virtual World,

vol. 16, number 3-4, 153-161.

Wingo Sai-Keung WONG



[ Movie avi 19M ]

An Intrinsic Collision Detection Unit (ICDU) forms the bottom-most layer of a collision detection pipeline. The ICDU performs collision detection and computes collision information for primitive feature pairs of objects in a 3D dynamic environment. A significant amount of time can be spent by the ICDU during the collision detection process. In this paper, we extend the ICDU framework to take advantages of the computational power of programmable graphics processors (GPUs). Some components of the ICDU framework consist of time demanding and fine-grained tasks that can be implemented on GPUs. By employing the framework, collision information can be computed accurately, robustly and efficiently. Experimental results show that the proposed method greatly improves the performance of the ICDU. A collection buffer is proposed for the future enhancement of GPU-based collision detectors.



Intrinsic Continuous Collision Detection for Deformable Meshes

W.S.-K. Wong and G. Baciu,

Research Journal of Textile and Apparel, vol. 9, number 1, 60-73.

Wingo Sai-Keung WONG


We propose an architecture for the intrinsic collision detection unit to perform collision detection for deformable triangular meshes, accurately, robustly and efficiently. We adopt a cache scheme which greatly improves the feature (e.g. point, edge and triangle) collision detection and thus improves the overall collision detection process. Our method handles numerical errors appropriately. Therefore, it accurately reports all the first contact points and collision information. Moreover, the method tracks collision orientations inherently so that proper action can be taken in order to avoid inter-penetrations. This method suits to meshes in a highly contact virtual environment in which the number of contact points is large. We illustrate an example of the applications of the method in cloth simulation.




Dynamics Interaction between Deformable Surfaces and Nonsmooth Objects

W.S.-K. Wong and G. Baciu,

Transactions on Visualization and Computer Graphics, vol. 11, number 3, 329-340.

Wingo Sai-Keung WONG



In this paper, we introduce new techniques that enhance the computational performance for the interactions between sharp objects and deformable surfaces. This is based on a time-domain predictor-corrector model. For this purpose we define a new kind of $(\pi, \beta, \mbf{I})$-surface. The partitioning of a deformable surface into a finite set of  $(\pi, \beta, \mbf{I})$-surfaces allows us to prune a large number of non-colliding feature pairs. This leads to a significant performance improvement in the collision detection process. The intrinsic collision detection is performed in the time domain. Although it is more expensive compared to the static interference test, it avoids portions of the surfaces passing through each other in a single time step. In order to resolve all the possible collision events at a given time,  a penetration-free motion space is constructed for each colliding particle. By keeping the velocity of each particle inside the motion space, we guarantee that the current colliding feature pairs  will not penetrate each other in the subsequent motion. A static analysis approach is adopted to handle friction by considering the forces acting on the particles and their velocities. In our formulation, we further reduce the computational complexity by eliminating the need to compute repulsive forces.


Movies Download

QuickTime Movies

[Entire Sequence [long version]: 49.3MB] : close-up and zoom out views [low quality]

[Entire Sequence [short version]: 13.1MB] : [low quality, fast]



[ 1. Slope closeup: 4.5MB ] [ Slope: 8.6MB ]

[ 2. Nails closeup: 8.4MB ] [ Nails: 8.0MB ]

[ 3. Sliding closeup: 14.0MB ] [ Sliding: 13.2MB ]

[ 4. Bumpy closeup: 7.8MB ] [ Bumpy zoom out: 7.3MB ]

[ 5. Draping closeup: 4.2MB ] [ Draping: 4.5MB ]

[ 6. Windy closeup: 13.2MB ] [ Windy zoom out: 12.7MB ]


Complex Self-Interaction of Deformable Surface



QuickTime Movie

[ Multi-ribbon : 12.8 MB ]

Complex interaction  of a multi-ribbon.


Skirt Draping and Fluttering

QuickTime Movie

[ Skirt : 5.5 MB ]

 Skirt draping and fluttering.



Flag Simulation

Wingo Sai-Keung WONG


Abstract: A spring-mass system is used for modeling a flag. The motion of the flag is under the effect of gravitational force and a virtual wind. There is no collision detection nor response enabled.


VRST'02 Demo Movies

Wing Sai-Keung WONG


Abstract: There are two clips. In one clipe there are four movies. Each movie is played twice. The movies are:
(1) a U-shape surface with some fixed points falling over three half-sphere tables;
(2) two carpets falling over three spheres;
(3) a carpet falling over a female model with two hands flung out;
(4) a carpet falling over a standing female model.
In another clip, there are some snows flying under the effect of gravitational force and virtual wind. And also there is a carpet and its fringes are moving freely under the forces.


| Movie 1 | Movie 2 | Movie 3 | Movie 4 | Movie 5 | Movie 6 |


Motion Capture and Synthesis

Iu Ka Chun Bartholomew


Abstract: Motion capture is a technology in the 3D computer modeling to get the locus of a moving object into data that can be processed by 3D computer programs. One of the key drawbacks of motion capture is that it does not have the ability to handle post-processing of the captured data. Even though several commercial tools are already available to handle the post-processing, post-capture motion editing remains one of the most active research areas in the field of computer animation. One of the real challenges of motion editing is to create motion for the imaginary creatures. In this project, we first explore different techniques for editing motion and apply one of these techniques to implement a cross-platform motion editing system using OpenGL, C and C++.


City Modelling

Sun Jing


Abstract: Here we propose a novel method to generate a virtual traffic network based on patterns and templates. Using 2D images as input maps, various road maps with different patterns could be produced. This traffic network generating model adjusts itself intelligently in order to avoid restricted geographical areas or urban developments. The generative model follows closely directions of elevation and connects road ends in ways that allow various types of breakpoints.


Surface Intersection



Abstract: We propose a subdivision approach to compute the intersections between two surfaces of revolution. Each surface of revolution is subdivided into a series of co-axial bounded revolute quadrics and hence the intersection problem is reduced into computing the intersections between two revolute quadrics. This demo shows that in most cases our method is faster than the fastest currently known method which is an analytical based approach.


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