Research On Simulation Of Fabric Deformation With Cutting And Colliding Feedback

Over the last few decades, fabrics simulation has become an important field of computer graphics, because of its unique characteristics. Due to the increasing applications, such as animation and film, video games, clothing design, virtual dressing room, visual simulation of fishing, and even propeller with anti-nets wrapping function design, there is a demand for the fabric simulation with colliding and tearing feedback. It can be effectively achieved by combining the physic engine, such as PhysX. However, the source code of PhysX is non-open,hence we cannot make any modification of the code or the algorithm embedded in it arbitrarily. Therefore, we both attempt to code for the basic algorithms of key technologies without using physic engine, and establish the fabric simulation with cutting and twining feedback based on PhysX as well. Therefore, we can achieve a primary theoretical understanding, and also satisfy the requirements of the simulation system. The key technologies mainly include model construction, collision detection algorithm, data structure updating and fabrics model remeshing. We develop this paper into the following parts.Firstly, we establish the model of the soft fabrics. After introducing the basic mass-spring model and its dynamic analysis, we combine sheet-level and yarn-level mass-spring model to construct the physic model of soft fabrics, in order to describe more details of the fabrics after being cut. Moreover, we use Verlet integration algorithm, instead of Euler algorithm to calculate the displacement and the deformation of the fabrics, thus we can achieve more effective and more robust results. Meanwhile, we introduced the ray method to project the 2D position of the mouse to pick the 3D position of the fabrics. At last, the experimental results verify the advantage of verlet algortithm over the Euler method and the feasibility of the ray method.Secondly, we design the cutting process. After analyzing the dynamics of fabric model,we set the force range of the spring. When an external force exceeds the maximum at a certain spring, the spring will break here and mesh topology will change. Then we design a reconstruction algorithm to update the data structure and topology of the fabrics.Again, we design a novel and efficient collision detection algorithm. On the basis of mass-spring model, we import 3D geometric model of rigid body, the scissors. Then we use hierarchical AABB bounding volume based on the structure of binary tree to surround the scissors, and then they turn to physical model. When they collide with the fabrics, we detect the collision between the hierarchical bounding volumes and the triangles of the fabric model.As for the twinkles and folds of the fabrics after the collision, we use the edge-edge method to detect the self-collision of the fabrics. In order to verify the feasibility of the algorithms, we make experiments of bounding volumes establishing and elements intersecting. And also, in order to indicate colliding effects more apparently, we combine PhysX to build a colliding experiment between rigid bodies and the soft fabric meshes.Finally, we establish the software based on the Physx to obtain the fabric simulation with colliding and tearing feedback. We package the 3D geometric model of the scissors model within capsules which are a kind of basic elements in PhysX, so that the geometric model turns into physic model. Therefore, we achieve the colliding and cutting simulation between the scissors and the fabric model.