Projects
This is a selection of projects I was involved in. Please refer to the publications page for a full list of publications covering all my work in computer graphics and computer vision.- Relighting Objects from Image Collections
- Massively-Parallel Simulation of Biochemical Systems
- Multi-View Stereo for Community Photo Collections
- Multi-View Stereo Revisited
- Mesostructure from Specularity
- Volumetric Density Capture From a Single Image
- DISCO - Acquisition of Translucent Objects
- Validation of Color Managed 3D Appearance Acquisition
- Accurate Light Source Acquisition and Rendering
- Image-Based Reconstruction of Spatially Varying Materials
- Accuracy of 3D Range Scanners by Measurement of the Slanted Edge Modulation Transfer Function
- Interactive Rendering of Translucent Objects
Relighting Objects from Image CollectionsWe present an approach for recovering the reflectance of a static scene with known geometry from a collection of images taken under distant, unknown illumination. In contrast to previous work, we allow the illumination to vary between the images, which greatly increases the applicability of the approach. Using an all-frequency relighting framework based on wavelets, we are able to simultaneously estimate the per-image incident illumination and the per- surface point reflectance. The wavelet framework allows for incorporating various reflection models. We demonstrate the quality of our results for synthetic test cases as well as for several datasets captured under laboratory conditions. Combined with multi-view stereo reconstruction, we are even able to recover the geometry and reflectance of a scene solely using images collected from the Internet.Relighting Objects from Image Collections |
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Massively-Parallel Simulation of Biochemical SystemsUnderstanding biological evolution prompts for a detailed understanding of the realized phenotype. Biochemical and gene regulatory dynamics are a cornerstone for the physiology of the cell and must therefore be regarded as one of the major aspects of such a phenotype. Experimental insight into molecular parameters is, however, hard to come by. Model development therefore requires computational parameter estimation. At the same time, design of cellular dynamics is highly efficient when done in-silico. We therefore developed a computational approach to allow for massively parallel simulation of biological molecular networks that leverage the massively-parallel computing power of modern graphics cards and other many-core programming paradigms. Our system can automatically compile standard SBML files into CUDA code, using analytic derivatives, and computing standard measures of complex dynamics like the Lyapunov exponent.Massively-Parallel Simulation of Biochemical Systems |
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Multi-View Stereo for Community Photo CollectionsWe present a multi-view stereo algorithm that addresses the extreme changes in lighting, scale, clutter, and other effects in large online community photo collections. Our idea is to intelligently choose images to match, both at a per-view and per-pixel level. We show that such adaptive view selection enables robust performance even with dramatic appearance variability. The stereo matching technique takes as input sparse 3D points reconstructed from structure-from-motion methods and iteratively grows surfaces from these points. Optimizing for surface normals within a photoconsistency measure significantly improves the matching results. While the focus of our approach is to estimate high-quality depth maps, we also show examples of merging the resulting depth maps into compelling scene reconstructions. We demonstrate our algorithm on standard multi-view stereo datasets and on casually acquired photo collections of famous scenes gathered from the Internet..Multi-View Stereo for Community Photo Collections More Information is available at the project page and at our community photo collections (CPC) page. |
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Multi-View Stereo RevisitedWe present an extremely simple yet robust multi-view stereo algorithm and analyze its properties. The algorithm first computes individual depth maps using a window-based voting approach that returns only good matches. The depth maps are then merged into a single mesh using a straightforward volumetric approach. We show results for several datasets, showing accuracy comparable to the best of the current state of the art techniques and rivaling more complex algorithms.
Multi-View Stereo Revisited
The reconstructed geometry models have been submitted to the Multi-View Stereo Evaluation. See the latest results for a comparison to other current approaches. |
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Mesostructure from SpecularityWe describe a simple and robust method for surface mesostructure acquisition. Our method builds on the observation that specular reflection is a reliable visual cue for surface mesostructure perception. In contrast to most photometric stereo methods, which take specularities as outliers and discard them, we propose a progressive acquisition system that captures a dense specularity field as the only information for mesostructure reconstruction. Our method can efficiently recover surfaces with fine-scale geometric details from complex real-world objects with a wide variety of reflection properties, including translucent, low albedo, and highly specular objects. We show results for a variety of objects including skin, apricot, orange, jelly candy, black leather and dark chocolate.
Mesostructure from Specularity
More information is available on Tongbo Chen's project page at the MPI Informatik. |
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Volumetric Density Capture From a Single ImageWe propose a new approach to capture the volumetric density of scattering media instantaneously with a single image. The volume is probed with a set of laser lines and the scattered intensity is recorded by a conventional camera. We then determine the density along the laser lines taking the scattering properties of the media into account. A specialized interpolation technique reconstructs the full density field in the volume. We apply the technique to capture the volumetric density of participating media such as smoke.
Density Estimation for Dynamic Volumes
Volumetric Density Capture From a Single Image
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DISCO - Acquisition of Translucent ObjectsTranslucent objects are characterized by diffuse light scattering beneath the object's surface. Light enters and leaves an object at possibly distinct surface locations. This paper presents the first method to acquire this transport behavior for arbitrary inhomogeneous objects. Individual surface points are illuminated in our DISCO measurement facility and the object's impulse response is recorded with a high-dynamic range video camera. The acquired data is resampled into a hierarchical model of the object's light scattering properties. Missing values are consistently interpolated resulting in measurement-based, complete and accurate representations of real translucent objects which can be rendered with various algorithms.
DISCO - Acquisition of Translucent Objects
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Validation of Color Managed 3D Appearance AcquisitionImage-based appearance acquisition algorithms are able to generate realistic 3D models of real objects but have previously not taken care of calibrated color space. We integrate a color managed high-dynamic range imaging technique into a recent appearance acquisition algorithm and generate models in CIE XYZ color space. We compare the final models with spectrophotometric measurements and compute difference images between renderings and ground truth images. Displayed renderings and printouts are compared to the original objects under identical illumination conditions to evaluate and validate the complete appearance reproduction pipeline. Working in CIE XYZ color space allows for expressing the perceivable differences in a standardized measure.
Validation of Color Managed 3D Appearance Acquisition
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Accurate Light Source Acquisition and RenderingRealistic image synthesis requires both complex and realistic models of real-world light sources and efficient rendering algorithms to deal with them. In this paper, we describe a processing pipeline for dealing with complex light sources from acquisition to global illumination rendering. We carefully design optical filters to guarantee high precision measurements of real-world light sources. We discuss two practically feasible setups that allow us to measure light sources with different characteristics. Finally, we introduce an efficient importance-driven photon emission algorithm for our representation that can be used, for example, in conjunction with Photon Maps.
Accurate Light Source Acquisition and Rendering
Interactive Visualization of Complex Real-World Light Sources
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Image-Based Reconstruction of Spatially Varying MaterialsThe use of realistic models for all components of images synthesis is a fundamental prerequisite for photorealistic rendering. The generation of these models in a manual process often becomes infeasible as the demand for visual complexity increases steadily. We concentrate on the acquisition of realistic materials. In particular, we describe an acquisition method for shift-variant BRDFs, i.e., a specific BRDF for each surface point.
Image-Based Reconstruction of Spatial Appearance and Geometric Detail
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Accuracy of 3D Range Scanners by Measurement of the Slanted Edge Modulation Transfer FunctionWe estimate the accuracy of a 3D range scanner in terms of its spatial frequency response. We determine a scanner's modulation transfer function (MTF) in order to measure its frequency response. A slanted edge is scanned from which we derive a superresolution edge profile. Its Fourier transform is compared to the Fourier transform of an ideal edge in order to determine the MTF of the device. This allows us to determine how well small details can be acquired by the 3D scanner. We report the results of several measurements with two scanners under various conditions.
Accuracy of 3D Range Scanners by Measurement of the Slanted Edge Modulation Transfer Function
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Interactive Rendering of Translucent ObjectsWe present a rendering method for translucent objects, in which view point and illumination can be modified at interactive rates. In a preprocessing step the impulse response to incoming light impinging at each surface point is computed and stored in two different ways: The local effect on close-by surface points is modeled as a per-texel filter kernel that is applied to a texture map representing the incident illumination. The global response (i.e. light shining through the object) is stored as vertex-to-vertex throughput factors for the triangle mesh of the object. During rendering, the illumination map for the object is computed according to the current lighting situation and then filtered by the precomputed kernels. The illumination map is also used to derive the incident illumination on the vertices which is distributed via the vertex-to-vertex throughput factors to the other vertices. The final image is obtained by combining the local and global response. We demonstrate the performance of our method for several models.
Interactive Rendering of Translucent
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