Improved Collision Detection and Response Techniques for Cloth Animation

In the animation of deformable objects, collision detection and response are crucial for the performance. Contrary to volumetric bodies, the accuracy requirements for the collision treatment of textiles are particularly strict because any overlapping is visible. Therefore, we apply methods specifically designed for deformable surfaces that speed up the collision detection. In this paper the efficiency of bounding volume hierarchies is improved by adapted techniques for building and traversing these hierarchies. An extended set of heuristics is described that allows to prune the hierarchy. Oriented inflation of bounding volumes enables us to detect proximities with a minimum of extra cost. Eventually, the distance of the mesh faces is computed accurately, and constraints respond to the collisions

A Finite Element Method for Interactive Physically Based Shape Modelling with Quadratic Tetrahedra

We present an alternative approach to standard geometric shape editing using physically-based simulation. With our technique, the user can deform complex objects in real-time. The enabling technology of this approach is a fast and accurate finite element implementation of an elasto-plastic material model, specifically designed for interactive shape manipulation. Using quadratic shape functions, we avoid the inherent drawback of volume locking exhibited by methods based on linear finite elements. The physical simulation uses a tetrahedral mesh, which is constructed from a coarser approximation of the detailed surface. Having computed a deformed state of the tetrahedral mesh, the deformation is transferred back to the high detail surface. This can be accomplished in an accurate and efficient way using the quadratic shape functions. In order to guarantee stability and real-time frame rates during the simulation, we cast the elasto-plastic problem into a linear formulation. For this purpose, we present a corotational formulation for quadratic finite elements. We demonstrate the versatility of our approach in interactive manipulation sessions and show that our animation system can be coupled with further physics-based animations like, e.g. fluids and cloth, in a bi-directional way

Pathogenic Fungi Regulate Immunity by Inducing Neutrophilic Myeloid-Derived Suppressor Cells

Peer reviewedPublisher PD

The C5a/C5a receptor 1 axis controls tissue neovascularization through CXCL4 release from platelets

Platelets contribute to the regulation of tissue neovascularization, although the specific factors underlying this function are unknown. Here, we identified the complement anaphylatoxin C5a-mediated activation of C5a receptor 1 (C5aR1) on platelets as a negative regulatory mechanism of vessel formation. We showed that platelets expressing C5aR1 exert an inhibitory effect on endothelial cell functions such as migration and 2D and 3D tube formation. Growth factor- and hypoxia-driven vascularization was markedly increased in C5ar1(−/−) mice. Platelet-specific deletion of C5aR1 resulted in a proangiogenic phenotype with increased collateralization, capillarization and improved pericyte coverage. Mechanistically, we found that C5a induced preferential release of CXC chemokine ligand 4 (CXCL4, PF4) from platelets as an important antiangiogenic paracrine effector molecule. Interfering with the C5aR1-CXCL4 axis reversed the antiangiogenic effect of platelets both in vitro and in vivo. In conclusion, we identified a mechanism for the control of tissue neovascularization through C5a/C5aR1 axis activation in platelets and subsequent induction of the antiangiogenic factor CXCL4

Continuous Motion Morphing

We present an extension to a previous morphing method for human motion. It works on motion capture data that is segmented into movement elements. Our new timewarping algorithm accepts time-dependent continuous functions as input for the morphing coefficients without introducing foot sliding. It is designed for creating new natural looking motions from given prototype motions. We employ a zero-moment-point criterion to analyze the physical correctness of the morphed motions

Johannes Mezger, Winfried Ilg, Martin Giese

We present an extension to a previous morphing method for human motion. It works on motion capture data that is segmented into movement elements. Our new timewarping algorithm accepts time-dependent continuous functions as input for the morphing coe#cients without introducing foot sliding. It is designed for creating new natural looking motions from given prototype motions. We employ a zero-moment-point criterion to analyze the physical correctness of the morphed motions

Progress in collision detection and response techniques for cloth animation

In the animation of deformable objects, collision detection and response are crucial for the performance. Furthermore, a physically correct cloth simulation requires robust collision avoidance, since any overlapping is visible and often results in expensive correction procedures. Much progress has been achieved in improving the numerical solution, and therefore most animations employ large time steps for fast simulations. This even more demands for accurate collision detection and response. In this work we show how collision detection for deformable meshes can be extended to detect proximities in advance. Several heuristics are introduced to save computation time, and constraints ensure an accurate collision response. 1 Previous work Many collision detection methods for various purposes have been developed in the past. Some of them are employed and adapted for the particular requirements of cloth modelling. Object-based methods represent the meshes hierarchically with bounding volumes [5, 6, 7]. In contrast, regular grids partition the scene into voxels [8]. In order to reduce the complexity of the self-collision test for deformable meshes, curvature heuristics are applied [6]. Particularly the distribution of the surface normals is suited to measure the surface curvature [4]. There are basically two different approaches to respond to collisions, namely the constraint based method [1] and the adjustment of position, velocity, and acceleration for the colliding particles [7]. Additionally, several techniques have been proposed to handle multiple collisions [4, 7]. 2 Dynamic �-DOP-Hierarchy Collision detection methods other than bounding volume hierarchies are mostly inapplicable to detect, on the on

Trajectory Synthesis by Hierarchical Spatio-temporal Correspondence: Comparison of Different Methods

We present several methods for the generation of complex human motion trajectories by linear combination of prototypical example trajectories with well-defined styles. These methods decompose longer trajectories automatically into movement primitives by robust matching with stored templates. To synthesize movement primitives with new style properties, segments from the prototype trajectories are linearly combined. These linear combinations are based on the computation of spatio-temporal correspondence between trajectory segments. The synthesized new movement primitives are automatically concatenated into longer action sequences, trying to minimize artifacts at the transition points. The proposed methods are evaluated by synthesizing movement sequences from martial arts ("karate katas") that include movements primitives with different styles. For assessing the physical correctness of the generated movements we employ a zero-moment-point criterion. This physical measure was very similar for real human movement trajectories and trajectories synthesized by linear combination. In addition, we evaluated the perceptual quality of the synthesized movement sequences in a psychophysical study, involving naive subjects and computer graphics experts. We found significant differences between the different methods. For complex movements methods based on space-time correspondence seem to outperform algorithms without time-warping. In addition, computer graphics experts seem to be more sensitive to artifacts in the trajectories than normal observers