Mirko Sattler

Acquisition, Synthesis, and Rendering of Bidirectional Texture Functions

One of the main challenges in computer graphics is still the realistic rendering of complex materials such as fabric or skin. The difficulty arises from the complex meso structure and reflectance behavior defining the unique look‐and‐feel of a material. A wide class of such realistic materials can be described as 2D‐texture under varying light‐ and view direction, namely, the Bidirectional Texture Function (BTF). Since an easy and general method for modeling BTFs is not available, current research concentrates on image‐based methods, which rely on measured BTFs (acquired real‐world data) in combination with appropriate synthesis methods. Recent results have shown that this approach greatly improves the visual quality of rendered surfaces and therefore the quality of applications such as virtual prototyping. This state‐of‐the‐art report (STAR) will present the techniques for the main tasks involved in producing photo‐realistic renderings using measured BTFs in details.

Exploitation of human shadow perception for fast shadow rendering

In this paper we describe an experiment to obtain information about the perceptual potential of the human visual system regarding shadow perception. Shadows play an important part for communicating spatial structures of objects to the observer. They are also essential for the overal realism of the rendered image. Unfortunately, most algorithms in computer graphics which are capable of producing realistic shadows are computationally expensive. The main idea behind the experiment is to use a simplified version of the shadow caster to generate hard and soft shadows, which would rapidly increase performance and to evaluate up to which degree a simplification is possible, without producing noticeable errors. Therefore, an experiment is performed, in which the test persons should mark the point of the just noticeable difference. First results show, that a mesh simplified to only 1% of its original complexity is capable to cast soft shadows that satisfy 90% of the test persons.

Realtime Shading of Folded Surfaces

In this paper we present a new, simple, and efficient way to illuminate folded surfaces with extended light sources in realtime including shadows. In a preprocessing step we compute the parts of the surrounding environment that are visible from a set of points on the surface and represent this information in a binary visibility map.

Probabilistic motion sequence generation

Creating long animation sequences with nontrivial repetitions is a time consuming and often difficult task. This is true for 2D images and even more true for 3D sequences. Based upon the idea of video textures we propose a simple algorithm to create new user controlled animation sequences based only on a few key frames by the analysis of velocity and position coherence. The simplicity of the method is achieved by carrying out the calculations on the main principal components of the reference animation, hence reducing the dimensionality of the input data. This also leads to significant compression. Smooth animations are ensured, using one of the proposed blending schemes