XX.7. Towards real-time Virtual Dressed Humans
XX.7.3. Interactive clothing system
We take advantage of the new advances brought by algorithms in our software 5355 by highly improving the garment generation and simulation speed.
Figure 23, Figure 24 and Figure 25 illustrate how garments are assembled around the body and seamed together.
Figure 23. Initial panel and seaming elastics.
Figure 24. Final garments, after adjustments
The main improvement from the results of our previous work is the computation time. The results above were obtained on a 150MHz R5000 SGI Indy, and take into account mechanical simulation computation as well as full collision detection and self-collision detection. As soon as the cloth begins to fit the body, collision detection becomes the major computation weight, which reached more than 70% in this exam-ple. Implementing incremental collision detection algorithms could reduce this.
Interactive cloth applications represent a wide subject at the crossroads; image synthesis, human animation, cloth design and Virtual Reality. We contribute by pro-viding through this work a fast and robust mechanical simulation system. No more complicated than a simple spring-mass particle system, it however simulates quite accurately an elastic material discretised into any irregular triangle mesh. Associated with Runge-Kutta integration and using numerical error evaluations as damping posi-tion and speed correcposi-tions, our model is robust, and yet powerful by keeping compu-tation timesteps high. A powerful constraint integration scheme also provides a pow-erful way of handling collisions, as well as a general support for extra interaction and manipulation tools.
Figure 25. Dressing a virtual actor: from initial panels to animation.
Suited for complicated garment simulations as well as for interactive clothing tools, applications may be extended in any direction of the crossroad. We demonstrate the model’s efficiency by some simple examples showing the speed, robustness, flexibility, and adaptability for tracking devices and Virtual Reality applications.
We want to take advantage of this potential to push further in the direction of inter-active clothing applications. First, a powerful set of virtual tools would allow us to design, assemble and manipulate garments in a very natural way, enabling us to visu-ally “feel” the fabric material in the 3D space. Then, using our VLNET system 38, we are preparing tools and techniques for a collaborative interactive system where distant partners together design and fit a common dress on a virtual being.
XX.8. Conclusion
We have described an efficient approach to model the human body for virtual hu-mans/clones based on default adaptive templates body parts. The main advantage of
the method is the use of body parts templates that are deformed to create new in-stances of the same body parts. As the shape deformations are used to automatically update the animation structure of the template to the new instance without additional manipulations, the modeling process is much simpler and efficient than the traditional approach. It provides a powerful framework to create virtual humans or clones ready to be embedded inside VR environments and animated. Some additional advantages of the proposed human body shape modeling approach are:
ü versatility: the modeling approaches can be applied and combined according to the given context, depending on the availability of the person to clone and the data we can get from them (photos, pictures scanned from a magazine), also de-pending on the time available for modeling the shape.
ü simplicity: it uses low cost, widely available equipment such as cameras to cap-ture the body parts shape.
Integrating the modeling approach together with efficient and scalable human body animation models, such as the one describe for hands simulation, inside a Networked Collaborative Virtual Environment such as VLNET, dedicated to management of virtual humans evolving and interacting inside a virtual environment, makes possible the development of real-time interactive performances such as CyberDance. The in-troduction of Deformation LODs (D-LODs) based on a scalable deformation model allows adaptation of the animation time consumption to the requested frame speed.
Further adaptation of research should be focused in two directions. The first one re-garding body modeling would extend the proposed approaches to any body part, in-cluding modeling the hair, and define a versatile framework to extract information from various inputs (pictures, anthropometric parameters, etc.). The second consists of developing strategies in order to dynamically switch between two D-LODs, and control the transition between the two D-LODs.
In order to reach a believable level of realism, simulating virtual bodies is not enough. Accessories such as clothes have also to be integrated in the virtual human modeling and simulation. Traditionally, clothes simulation requires physics based simulation. This usually means slow simulation models, unsuitable for real-time envi-ronments . We have shown that the clothes problem is not limited to the simulation of the clothes behavior. We also need to design clothes, manipulate them and dress vir-tual humans. Although we are not yet able to integrate clothes with virvir-tual humans in real time environments, our current research on clothes show that we are on the way to be able to interactively design clothes and dress virtual humans. We are also near to having virtual dressed humans evolving in real-time inside a virtual environment.
XX.9. Acknowledgements
This research is funded by SPP Swiss research program, The Swiss National Sci-ence Foundation and EU ESPRIT Project eRENA (Electronic Arenas for Culture, Performance, Art and Entertainment). The authors thank Christopher Joslin for proof reading this document.
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