Section: Scientific Foundations

3D Garment Simulation

Participants : Yujun Chen, Weiran Yuan, Tung Le Thanh, Thibault Luginbühl, André Gagalowicz.

Mechanical Modeling of Textile Materials

Usual geometric modeling is not sufficient to simulate cloth: an in-depth knowledge of fabrics behavior is required. Relations between stress and strain have to be dealt with, that are not defined by ordinary differential equations. Since analytical solutions are not available, numerical models are used; we have chosen mass-spring systems.

These models have to be fed with correct parameters. The Kawabata Evaluation System is the de-facto industry standard for fabrics measurements (limited to warp/weft textile materials): it operates typical deformations upon cloth samples and evaluates the resulting stress, which provides digital data. Our textile models are now able to simulate precisely Kawabata curves of real textile for tension, shear and bending.

Dynamic Garment Simulation

Once a numerical model of cloth is established, we have to produce complete garments. The technique we use directly comes from the textile industry. We use the same 2D patterns as those really manipulated by garment designers. This incorporates sewing information. We have to construct the garment automatically from this data. It appears to be a very complex problem, not solved in the literature (and even almost never tackled !). our goal is then to compute the evolution of this complete mass/spring system with respect to time; it relies on the integration of the fundamental equation of dynamics. Several families of algorithms exist, adequation to the underlying problem of which vary both in terms of stability and computation time. Checking the validity of our approach is also a very strong challenge that we began to undertake.

Handling contact phenomenon between pieces of cloth, and the characters that wear them is the other big challenge: large amounts of data have to be processed to accurately detect possible collisions, and a realistic model has to be used once an actual collision has been detected.

Regularization and colorization of 3D human body shapes coming from 3D scanners

In order to design a virtual try-on system, it is necessary to scan both geometrically and photometrically the 3D body of clients. All 3D scanners produce only partial results due to the non convexity of human bodies and to misses of the scanner on the projected patterns reconstruction. Resulting holes in the geometrical shape reconstruction are unacceptable for any simulation software. So, it is fundamental to regularize the surface. We also need to produce full color representations of the clients so that they can obtain a faithful picture of themselves wearing virtually the garment they chose to try. Such scanners still do not exist and we are interested by the design of such scanners through the collaboration with a scanner manufacturor.