Title: Liquid Surface Tracking with Error Compensation
Publication: SIGGRAPH 2013
WWW: http://visualcomputing.ist.ac.at/publications/2013/LSTwEC/

Authors:
Morten Bojsen-Hansen (IST Austria)
Chris Wojtan (IST Austria)

Abstract: Our work concerns the combination of an Eulerian liquid simulation with a high-resolution surface tracker (e.g. the level set method or a Lagrangian triangle mesh). The naive application of a high-resolution surface tracker to a low-resolution velocity field can produce many visually disturbing physical and topological artifacts that limit their use in practice. We address these problems by defining an error function which compares the current state of the surface tracker to the set of physically valid surface states. By reducing this error with a gradient descent technique, we introduce a novel physics-based surface fairing method. Similarly, by treating this error function as a potential energy, we derive a new surface correction force that mimics the vortex sheet equations. We demonstrate our results with both level set and mesh-based surface trackers.

When coding up fluid simulators, you often run into artifacts. Here is one of the 'happier' ones.

A fast forward or spotlight is a concept used at computer science conferences. In essence, it is a (very) short presentation used to advertise the full talk given later in the conference.

Speaker: Morten Bojsen-Hansen
Conference: SIGGRAPH 2016
WWW: http://visualcomputing.ist.ac.at/publications/2016/GNRBfFRS/

Title: Generalized Non-Reflecting Boundaries for Fluid Re-Simulation
Publication: SIGGRAPH 2016
WWW: http://visualcomputing.ist.ac.at/publications/2016/GNRBfFRS/

Authors:
Morten Bojsen-Hansen (IST Austria)
Chris Wojtan (IST Austria)

Abstract: When aiming to seamlessly integrate a fluid simulation into a larger scenario (like an open ocean), careful attention must be paid to boundary conditions. In particular, one must implement special "non-reflecting" boundary conditions, which dissipate out-going waves as they exit the simulation. Unfortunately, the state of the art in non-reflecting boundary conditions (perfectly-matched layers, or PMLs) only permits trivially simple inflow/outflow conditions, so there is no reliable way to integrate a fluid simulation into a more complicated environment like a stormy ocean or a turbulent river.

This paper introduces the first method for combining non-reflecting boundary conditions based on PMLs with inflow/outflow boundary conditions that vary arbitrarily throughout space and time. Our algorithm is a generalization of state-of-the-art mean-flow boundary conditions in the computational fluid dynamics literature, and it allows for seamless integration of a fluid simulation into much more complicated environments. Our method also opens the door for previously-unseen post-process effects like retroactively changing the location of solid obstacles, and locally increasing the visual detail of a pre-existing simulation.

A fast forward or spotlight is a concept used at computer science conferences. In essence, it is a (very) short presentation used to advertise the full talk given later in the conference.

Speaker: Morten Bojsen-Hansen
Conference: SIGGRAPH 2013
WWW: http://visualcomputing.ist.ac.at/publications/2013/LSTwEC/

A fast forward or spotlight is a concept used at computer science conferences. In essence, it is a (very) short presentation used to advertise the full talk given later in the conference.

Speaker: Morten Bojsen-Hansen
Conference: SIGGRAPH 2012
WWW: http://visualcomputing.ist.ac.at/publications/2012/TSwET/

Title: Tracking Surfaces with Evolving Topology
Publication: SIGGRAPH 2012
WWW: http://visualcomputing.ist.ac.at/publications/2012/TSwET/

Authors: Morten Bojsen-Hansen (IST Austria)
Hao Li (Columbia University)
Chris Wojtan (IST Austria)

Abstract: We present a method for recovering a temporally coherent, deforming triangle mesh with arbitrarily changing topology from an incoherent sequence of static closed surfaces. We solve this problem using the surface geometry alone, without any prior information like surface templates or velocity fields. Our system combines a proven strategy for triangle mesh improvement, a robust multi-resolution non-rigid registration routine, and a reliable technique for changing surface mesh topology. We also introduce a novel topological constraint enforcement algorithm to ensure that the output and input always have similar topology. We apply our technique to a series of diverse input data from video reconstructions, physics simulations, and artistic morphs. The structured output of our algorithm allows us to efficiently track information like colors and displacement maps, recover velocity information, and solve PDEs on the mesh as a post process.