Markus Wacker

A consistent bending model for cloth simulation with corotational subdivision finite elements

Wrinkles and folds play an important role in the appearance of real textiles. The way in which they form depends mainly on the bending properties of the specific material type. Existing approaches fail to reliably reproduce characteristic behaviour like folding and buckling for different material types or resolutions. It is therefore crucial for the realistic simulation of cloth to model bending energy in a physically accurate and consistent way. In this paper we present a new method based on a corotational formulation of subdivision finite elements. Due to the non-local nature of the employed subdivision basis functions a C1-continuous displacement field can be defined. In this way, it is possible to use the governing equations of thin shell analysis leading to physically accurate bending behaviour. Using a corotated strain tensor allows the large displacement analysis of cloth while retaining a linear system of equations. Hence, known convergence properties and computational efficiency are preserved while convincing and detailed folding behaviour is obtained in the simualtion.

Interactive physically based fluid and erosion simulation

Realistically eroded terrain is a base of almost every outdoor visualization for simulators or computer games. In order to achieve convincing results physically based erosion algorithms are necessary. We present a new method that combines a non-expensive fluid simulation with an erosion algorithm. Both parts are running at interactive rates so the artist is able to influence the erosion process in real-time by changing simulation parameters or applying additional water to the scene. In this way, we support realism as well as design aspects during the terrain creation process. To simplify the three dimensional fluid simulation we use a newtonian physics approach that works on a two dimensional grid storing acceleration, velocity and mass. The method provides all features that are important for simulation of erosion e.g. moving, non-moving water (rivers, lakes) and evaporation. This allows us to support effects like dissolving, transportation and sedimentation of material in the erosion process.

Garment motion capture using color-coded patterns

We present a new image-based algorithm for surface reconstruction of moving garment from multiple calibrated video cameras. Using a color-coded cloth texture, we reliably match circular features between different camera views. As surface model we use an a priori known triangle mesh. By identifying the mesh vertices with texture elements we obtain a coherent parameterization of the surface over time without further processing. Missing data points resulting from self-shadowing are plausibly interpolated by minimizing a thin-plate functional. The deforming geometry can be used for different graphics applications, e.g. for realistic retexturing. We show results for real garments demonstrating the accuracy of the recovered flexible shape.

Compressed Manifold Modes for Mesh Processing

This paper introduces compressed eigenfunctions of the Laplace‐Beltrami operator on 3D manifold surfaces. They constitute a novel functional basis, called the compressed manifold basis, where each function has local support. We derive an algorithm, based on the alternating direction method of multipliers (ADMM), to compute this basis on a given triangulated mesh. We show that compressed manifold modes identify key shape features, yielding an intuitive understanding of the basis for a human observer, where a shape can be processed as a collection of parts. We evaluate compressed manifold modes for potential applications in shape matching and mesh abstraction. Our results show that this basis has distinct advantages over existing alternatives, indicating high potential for a wide range of use‐cases in mesh processing.

Tailor tools for interactive design of clothing in virtual environments

In this work, we present virtual tailor tools which allow the interactive design and modification of clothing in a 3D Virtual Environment. In particular, we propose algorithms and interaction techniques for sewing and cutting garments during a physical cloth simulation, including the automatic modification of the underlying planar cloth patterns.

A comparative study on user performance in the Virtual Dressmaker application

We report on a user study, investigating the efficiency of user interaction in a Virtual Reality application compared to 3D desktop applications.The Virtual Dressmaker is a Virtual Reality application for virtual cloth design, assembly, and simulation that supports advanced 6DoF interaction techniques. We conjecture that these interaction techniques are more natural for the users and lead to faster and more precise results than common desktop applications.In our user study we investigate interaction tools for positioning garment patterns in VR and compare the results to interaction with common 3D desktop applications. We measure completion time and precision of the positioned patterns and evaluate the subjective impressions of the users.The results show that Virtual Environments, and the presented interaction tools in particular, provide a valuable method for cloth design and assembly. Moreover, certain features of current 3D desktop design tools can be exploited for further improvements of VR interaction.

Monocular Pose Reconstruction for an Augmented Reality Clothing System

In this paper, we present an approach for realizing an augmented reality system for try-on of apparel. The core component of our system is a quick human pose estimation algorithm based on a single camera view only. Due to monocular input data, pose reconstruction may be ambiguous. We solve this problem by using a markered suit, though not relying on any specific marker layout. To recover 3D joint angles of the person using the system we use Relevance Vector Machine regression with image descriptors that include neighborhood configurations of visible colored markers and image gradient orientations. This novel combination of image descriptors results in a measurable improvement in reconstruction quality. We initialize and evaluate our algorithm with pose data acquired using a motion capture system. As the final step, we simulate a cloth draped around a virtual character adopting the estimated pose. Composing the original view and the rendered cloth creates the illusion of the user wearing virtual garments.

High detail marker based 3D reconstruction by enforcing multiview constraints

We present a 3D reconstruction method enabling high resolution marker-based capturing of deforming surfaces. In contrast to previous work, we allow all markers to look exactly the same and do not rely on temporal tracking. This implies considerable advantages: markers can be smaller and are easier to apply due to omitted identification; long-range motions normally confusing temporal tracking algorithms become feasible. However, the correct matching of markers between camera views is highly ambiguous in such a scenario. To solve this problem we propose an optimization framework that considers multiview conflicts and local smoothness of the captured surface. An iterative relaxation method based on graph matching is adopted to obtain a consistent, smooth reconstruction for all stereo pairs of a multi-camera system simultanously. Preliminary experiments show excellent and robust results.

Combining biomechanical and data-driven body surface models

Statistical body shape modelling can be used to realistically generate complex muscle deformation effects on the skin. However, purely data-driven models still ignore the biomechanical nature of surface deformations. Reliable anatomically and biomechanically consistent predictions are barely possible. Our research aims at combining the previously separate paradigms - data-driven and simulation-driven 3D surface modeling - to a hybrid body shape model. Our first goal consists of synthesizing the skin surface from simulated biomechanical data. As a first step in this direction we show preliminary results of our model of an elbow flexion motion with separate biceps and triceps muscle bulging that exhibits believable muscular deformation effects on the skin surface while enabling singular control over specific muscle regions. Our model is separately controllable in shape and pose and extensible to a wider range of human body shapes, joint motion and muscle regions.