publications

2023

1. 

   Real-time light estimation and neural soft shadows for AR indoor scenarios

   Alexander Sommer, Ulrich Schwanecke, and Elmar Schömer

   Journal of WSCG, 2023

   Abs DOI Bib PDF

   We present a pipeline for realistic embedding of virtual objects into footage of indoor scenes with focus on real-time AR applications. Our pipeline consists of two main components: A light estimator and a neural soft shadow texture generator. Our light estimation is based on deep neural nets and determines the main light direction, light color, ambient color and an opacity parameter for the shadow texture. Our neural soft shadow method encodes object-based realistic soft shadows as light direction dependent textures in a small MLP. We show that our pipeline can be used to integrate objects into AR scenes in a new level of realism in real-time. Our models are small enough to run on current mobile devices. We achieve runtimes of 9ms for light estimation and 5ms for neural shadows on an iPhone 11 Pro.

   @article{Sommer23,
     title = {Real-time light estimation and neural soft shadows for {AR} indoor scenarios},
     author = {Sommer, Alexander and Schwanecke, Ulrich and Sch\"{o}mer, Elmar},
     year = {2023},
     journal = {Journal of WSCG},
     volume = {31},
     pages = {71--79},
     doi = {10.24132/jwscg.2023.8},
   }

2022

1. 

   Interactive high-resolution simulation of granular material

   Alexander Sommer, Ulrich Schwanecke, and Elmar Schömer

   Journal of WSCG, 2022

   Abs DOI Bib PDF

   We introduce a particle-based simulation method for granular material in interactive frame rates. We divide the simulation into two decoupled steps. In the first step, a relatively small number of particles is accurately simulated with a constraint-based method. Here, all collisions and the resulting friction between the particles are taken into account. In the second step, the small number of particles is significantly increased by an efficient sampling algorithm without creating additional artifacts. The method is particularly robust and allows relatively large time steps, which makes it well suited for real-time applications. With our method, up to 500k particles can be computed in interactive frame rates on consumer CPUs without relying on GPU support for massive parallel computing. This makes it well suited for applications where a lot of GPU power is already needed for render tasks.

   @article{Sommer22,
     title = {Interactive high-resolution simulation of granular material},
     author = {Sommer, Alexander and Schwanecke, Ulrich and Sch\"{o}mer, Elmar},
     year = {2022},
     journal = {Journal of WSCG},
     volume = {30},
     pages = {9--15},
     doi = {10.24132/jwscg.2022.2},
   }

2021

1. 

   LEAVEN - Lightweight surface and volume mesh sampling application for particle-based simulations

   Alexander Sommer and Ulrich Schwanecke

   Computer Science Research Notes, 2021

   Abs DOI Bib PDF Video Code

   We present an easy-to-use and lightweight surface and volume mesh sampling standalone application tailored for the needs of particle-based simulation. We describe the surface and volume sampling algorithms used in Leaven in a beginner-friendly fashion. Furthermore, we describe a novel method of generating random volume samples that satisfy blue noise criteria by modifying a surface sampling algorithm. We aim to lower one entry barrier for starting with particle-based simulations while still pose a benefit to advanced users. The goal is to provide a useful tool to the community and lowering the need for heavyweight third-party applications, especially for starters.

   @article{Sommer21,
     title = {{LEAVEN} - {L}ightweight surface and volume mesh sampling application for particle-based simulations},
     author = {Sommer, Alexander and Schwanecke, Ulrich},
     year = {2021},
     journal = {Computer Science Research Notes},
     volume = {31},
     number = {1},
     pages = {155--160},
     doi = {10.24132/csrn.2021.3101.17},
   }

2020

1. 

   Chebyshev’s method on projective fluids

   Alexander Sommer, Ulrich Schwanecke, and Elmar Schömer

   Journal of WSCG, 2020

   Abs DOI Bib PDF Video

   We demonstrate the acceleration potential of the Chebyshev semi-iterative approach for fluid simulations in Projective Dynamics. The Chebyshev approach has been successfully tested for deformable bodies, where the dynamical system behaves relatively linearly, even though Projective Dynamics, in general, is fundamentally nonlinear. The results for more complex constraints, like fluids, with a particular nonlinear dynamical system, remained unknown so far. We follow a method describing particle-based fluids in Projective Dynamics while replacing the Conjugate Gradient solver with Chebyshev’s method. Our results show that Chebyshev’s method can be successfully applied to fluids and potentially other complex constraints to accelerate simulations.

   @article{Sommer20,
     title = {Chebyshev's method on projective fluids },
     author = {Sommer, Alexander and Schwanecke, Ulrich and Sch\"{o}mer, Elmar},
     year = {2020},
     journal = {Journal of WSCG},
     volume = {28},
     number = {1--2},
     pages = {132--136},
     doi = {10.24132/jwscg.2020.28.16},
   }