Figure 1: Cable joints allow the fast and robust simulation of complicated arrangements of cables... more Figure 1: Cable joints allow the fast and robust simulation of complicated arrangements of cables by defining a single constraint for each cable segment between two contacts.
This paper introduces a novel method for simulating large bodies of water as a height field. At t... more This paper introduces a novel method for simulating large bodies of water as a height field. At the start of each time step, we partition the waves into a bulk flow (which approximately satisfies the assumptions of the shallow water equations) and surface waves (which approximately satisfy the assumptions of Airy wave theory). We then solve the two wave regimes separately using appropriate state-of-the-art techniques, and re-combine the resulting wave velocities at the end of each step. This strategy leads to the first heightfield wave model capable of simulating complex interactions between both deep and shallow water effects, like the waves from a boat wake sloshing up onto a beach, or a dam break producing wave interference patterns and eddies. We also analyze the numerical dispersion created by our method and derive an exact correction factor for waves at a constant water depth, giving us a numerically perfect re-creation of theoretical water wave dispersion patterns.
We examine the relationship between primal, or force-based, and dual, or constraint-based formula... more We examine the relationship between primal, or force-based, and dual, or constraint-based formulations of dynamics. Variational frameworks such as Projective Dynamics have proved popular for deformable simulation, however they have not been adopted for contact-rich scenarios such as rigid body simulation. We propose a new preconditioned frictional contact solver that is compatible with existing primal optimization methods, and competitive with complementarity-based approaches. Our relaxed primal model generates improved contact force distributions when compared to dual methods, and has the advantage of being differentiable, making it well-suited for trajectory optimization. We derive both primal and dual methods from a common variational point of view, and present a comprehensive numerical analysis of both methods with respect to conditioning. We demonstrate our method on scenarios including rigid body contact, deformable simulation, and robotic manipulation.
Eurographics Workshop on Parallel Graphics and Visualization, May 1, 2012
Figure 1: Visualization of a dynamic point cloud scene with 1 Million points. The raw point posit... more Figure 1: Visualization of a dynamic point cloud scene with 1 Million points. The raw point position data is streamed onto the GPU, where our algorithm performs an instant surface reconstruction that produces surface-aligned splats for illuminated rendering. The complete frame is computed in 94 ms at a resolution of of 1700 × 900 pixels.
This paper presents an analytic formulation for anti-aliased sampling of 2D polygons and 3D polyh... more This paper presents an analytic formulation for anti-aliased sampling of 2D polygons and 3D polyhedra. Our framework allows the exact evaluation of the convolution integral with a linear function defined on the polytopes. The filter is a spherically symmetric polynomial of any order, supporting approximations to refined variants such as the Mitchell-Netravali filter family. This enables high-quality rasterization of triangles and tetrahedra with linearly interpolated vertex values to regular and non-regular grids. A closed form solution of the convolution is presented and an efficient implementation on the GPU using DirectX and CUDA C is described.
This paper gives an overview of image-based representations commonly used for reducing the geomet... more This paper gives an overview of image-based representations commonly used for reducing the geometric complexity of a scene description in order to accelerate the rendering process. Several different types of representations and ways for using them have been presented, which are classified and discussed here. Furthermore, the overview includes techniques for accelerating the rendering of static scenes or scenes with animations and/or dynamic lighting effects. The advantages and drawbacks of the different approaches are illuminated, and unsolved problems and roads for further research are shown.
In this paper we present dart throwing algorithms to generate maximal Poisson disk point sets dir... more In this paper we present dart throwing algorithms to generate maximal Poisson disk point sets directly on 3D surfaces. We optimize dart throwing by efficiently excluding areas of the domain that are already covered by existing darts. In the case of triangle meshes, our algorithm shows dramatic speed improvement over comparable sampling methods. The simplicity of our basic algorithm naturally extends to the sampling of other surface types, including spheres, NURBS, subdivision surfaces, and implicits. We further extend the method to handle variable density points, and the placement of arbitrary ellipsoids without overlap. Finally, we demonstrate how to adapt our algorithm to work with geodesic instead of Euclidean distance. Applications for our method include fur modeling, the placement of mosaic tiles and polygon remeshing. 2. Previous Work Planar Methods. Cook [Coo86] was the first to suggest the use of Poisson disk sampling patterns in computer graphics. Noting the exorbitant cost of making such patterns by dart throwing, Cook advocated stratified samples as an alternative. Later, Lloyd [Llo87] described a simple relaxation procedure that could distribute points evenly, and Mitchell et al. [Mit91] removed the minimum distance requirement to produce the best candidate algorithm. Because of the difficulty of creating very large, well distributed point sets, tile-based approaches were developed that reuse smaller point sets within a larger context. Cohen et al. [CSHD03] showed how Wang tiles can be used to tile the plane seamlessly with well spaced points. Kopf et
The shape matching method is a popular approach to simulate deformable objects in interactive app... more The shape matching method is a popular approach to simulate deformable objects in interactive applications due to its stability and simplicity. An important feature is that there is no need for a mesh since the method works on arbitrary local groups within a set of particles. A major drawback of shape matching is the fact that it is geometrically motivated and not derived from physical principles which makes calibration difficult. The fact that the method does not conserve volume can yield visual artifacts, e.g. when a tire is compressed but does not bulge.In this paper we present a new meshless simulation method that is related to shape matching but derived from continuous constitutive models. Volume conservation and stiffness can be specified with physical parameters. Further, if the elements of a tetrahedral mesh are used as groups, our method perfectly reproduces FEM based simulations.
We propose a hierarchical graph for learning physics and a novel way to handle obstacles. The fin... more We propose a hierarchical graph for learning physics and a novel way to handle obstacles. The finest level of the graph consist of the particles itself. Coarser levels consist of the cells of sparse grids with successively doubling cell sizes covering the volume occupied by the particles. The hierarchical structure allows for the information to propagate at great distance in a single message passing iteration. The novel obstacle handling allows the simulation to be obstacle aware without the need for ghost particles. We train the network to predict effective acceleration produced by multiple sub‐steps of 3D multi‐material material point method (MPM) simulation consisting of water, sand and snow with complex obstacles. Our network produces lower error, trains up to 7.0X faster and inferences up to 11.3X faster than [SGGP*20]. It is also, on average, about 3.7X faster compared to Taichi Elements simulation running on the same hardware in our tests.
Simulating large bodies of water in real time has been a research goal for a few decades. Existin... more Simulating large bodies of water in real time has been a research goal for a few decades. Existing procedural approaches like FFT-based simulations typically lack dynamic response like boundary-wave reflections or general body-fluid interactions like splashes or boat wakes. On the other side of the spectrum, existing dynamic Eulerian wave simulations suffer from high memory consumption required for adequate grid sizes in large scenes. Dynamic Lagrangian simulations like wave particles suffer from a potentially prohibitive particle count.
Abstract—We present a method designed to address some limitations of typical route map displays o... more Abstract—We present a method designed to address some limitations of typical route map displays of driving directions. The main goal of our system is to generate a printable version of a route map that shows the overview and detail views of the route within a single, consistent visual frame. Our proposed visualization provides a more intuitive spatial context than a simple list of turns. We present a novel multi-focus technique to achieve this goal, where the foci are defined by points-of-interest (POI) along the route. A detail lens that encapsulates the POI at a finer geospatial scale is created for each focus. The lenses are laid out on the map to avoid occlusion with the route and each other, and to optimally utilize the free space around the route. We define a set of layout metrics to evaluate the quality of a lens layout for a given route map visualization. We compare standard lens layout methods to our proposed method and demonstrate the effectiveness of our method in generat...
Closest point map Initial guess Final image Rasterization Variable stencil diffusion Figure 1: Di... more Closest point map Initial guess Final image Rasterization Variable stencil diffusion Figure 1: Diffusion curve rendering in our system. Analytical curves (left) are rasterized into a closest point map (distance map plus information about the closest curve point) and an initial guess image (middle). The initial guess is diffused by our variable stencil size solver, producing the final image (right).
Point clouds, as a form of Lagrangian representation, allow for powerful and flexible application... more Point clouds, as a form of Lagrangian representation, allow for powerful and flexible applications in a large number of computational disciplines. We propose a novel deep-learning method to learn stable and temporally coherent feature spaces for points clouds that change over time. We identify a set of inherent problems with these approaches: without knowledge of the time dimension, the inferred solutions can exhibit strong flickering, and easy solutions to suppress this flickering can result in undesirable local minima that manifest themselves as halo structures. We propose a novel temporal loss function that takes into account higher time derivatives of the point positions, and encourages mingling, i.e., to prevent the aforementioned halos. We combine these techniques in a super-resolution method with a truncation approach to flexibly adapt the size of the generated positions. We show that our method works for large, deforming point sets from different sources to demonstrate the f...
This paper is a report about a project practical course (“Projektpraktikum”) done at the Institut... more This paper is a report about a project practical course (“Projektpraktikum”) done at the Institute for Computer Graphics and Algorithms of the Vienna University of Technology. Advisor: Stefan Jeschke. The goal of this course was to implement a texture synthesis algorithm and analyze its performance and visual quality. Two papers form the theoretical foundation of this project: “Texture Optimization for Example-based Synthesis” by Kwatra et al [KEBK05] and “Patchmatch: A randomized Correspondence Algorithm for Structural Image Editing” by Barnes et al [BSFG09].
Shape Arrays allow propagating arrays of shapes that adapt the number of elements to the surround... more Shape Arrays allow propagating arrays of shapes that adapt the number of elements to the surrounding geometry with a single placement propagation. The choice between scaling or repeating shapes to fill the bounding box of a placement can be specified separately for the width and height dimensions. To implement shape arrays, we specify a minimum spacing between shapes and find the maximum number of shapes that can be placed along the width and height dimensions while respecting this minimum spacing. The spacing is then adjusted so that there is no space before the first and after the last shape in both dimensions.
Proceedings of the ACM SIGGRAPH / Eurographics Symposium on Computer Animation, 2017
Figure 1: Long range constraints propagate errors through large stacks or long chains instantaneo... more Figure 1: Long range constraints propagate errors through large stacks or long chains instantaneously and make it possible to simulate the depicted scenes with a small number of solver iterations.
Figure 1: Cable joints allow the fast and robust simulation of complicated arrangements of cables... more Figure 1: Cable joints allow the fast and robust simulation of complicated arrangements of cables by defining a single constraint for each cable segment between two contacts.
This paper introduces a novel method for simulating large bodies of water as a height field. At t... more This paper introduces a novel method for simulating large bodies of water as a height field. At the start of each time step, we partition the waves into a bulk flow (which approximately satisfies the assumptions of the shallow water equations) and surface waves (which approximately satisfy the assumptions of Airy wave theory). We then solve the two wave regimes separately using appropriate state-of-the-art techniques, and re-combine the resulting wave velocities at the end of each step. This strategy leads to the first heightfield wave model capable of simulating complex interactions between both deep and shallow water effects, like the waves from a boat wake sloshing up onto a beach, or a dam break producing wave interference patterns and eddies. We also analyze the numerical dispersion created by our method and derive an exact correction factor for waves at a constant water depth, giving us a numerically perfect re-creation of theoretical water wave dispersion patterns.
We examine the relationship between primal, or force-based, and dual, or constraint-based formula... more We examine the relationship between primal, or force-based, and dual, or constraint-based formulations of dynamics. Variational frameworks such as Projective Dynamics have proved popular for deformable simulation, however they have not been adopted for contact-rich scenarios such as rigid body simulation. We propose a new preconditioned frictional contact solver that is compatible with existing primal optimization methods, and competitive with complementarity-based approaches. Our relaxed primal model generates improved contact force distributions when compared to dual methods, and has the advantage of being differentiable, making it well-suited for trajectory optimization. We derive both primal and dual methods from a common variational point of view, and present a comprehensive numerical analysis of both methods with respect to conditioning. We demonstrate our method on scenarios including rigid body contact, deformable simulation, and robotic manipulation.
Eurographics Workshop on Parallel Graphics and Visualization, May 1, 2012
Figure 1: Visualization of a dynamic point cloud scene with 1 Million points. The raw point posit... more Figure 1: Visualization of a dynamic point cloud scene with 1 Million points. The raw point position data is streamed onto the GPU, where our algorithm performs an instant surface reconstruction that produces surface-aligned splats for illuminated rendering. The complete frame is computed in 94 ms at a resolution of of 1700 × 900 pixels.
This paper presents an analytic formulation for anti-aliased sampling of 2D polygons and 3D polyh... more This paper presents an analytic formulation for anti-aliased sampling of 2D polygons and 3D polyhedra. Our framework allows the exact evaluation of the convolution integral with a linear function defined on the polytopes. The filter is a spherically symmetric polynomial of any order, supporting approximations to refined variants such as the Mitchell-Netravali filter family. This enables high-quality rasterization of triangles and tetrahedra with linearly interpolated vertex values to regular and non-regular grids. A closed form solution of the convolution is presented and an efficient implementation on the GPU using DirectX and CUDA C is described.
This paper gives an overview of image-based representations commonly used for reducing the geomet... more This paper gives an overview of image-based representations commonly used for reducing the geometric complexity of a scene description in order to accelerate the rendering process. Several different types of representations and ways for using them have been presented, which are classified and discussed here. Furthermore, the overview includes techniques for accelerating the rendering of static scenes or scenes with animations and/or dynamic lighting effects. The advantages and drawbacks of the different approaches are illuminated, and unsolved problems and roads for further research are shown.
In this paper we present dart throwing algorithms to generate maximal Poisson disk point sets dir... more In this paper we present dart throwing algorithms to generate maximal Poisson disk point sets directly on 3D surfaces. We optimize dart throwing by efficiently excluding areas of the domain that are already covered by existing darts. In the case of triangle meshes, our algorithm shows dramatic speed improvement over comparable sampling methods. The simplicity of our basic algorithm naturally extends to the sampling of other surface types, including spheres, NURBS, subdivision surfaces, and implicits. We further extend the method to handle variable density points, and the placement of arbitrary ellipsoids without overlap. Finally, we demonstrate how to adapt our algorithm to work with geodesic instead of Euclidean distance. Applications for our method include fur modeling, the placement of mosaic tiles and polygon remeshing. 2. Previous Work Planar Methods. Cook [Coo86] was the first to suggest the use of Poisson disk sampling patterns in computer graphics. Noting the exorbitant cost of making such patterns by dart throwing, Cook advocated stratified samples as an alternative. Later, Lloyd [Llo87] described a simple relaxation procedure that could distribute points evenly, and Mitchell et al. [Mit91] removed the minimum distance requirement to produce the best candidate algorithm. Because of the difficulty of creating very large, well distributed point sets, tile-based approaches were developed that reuse smaller point sets within a larger context. Cohen et al. [CSHD03] showed how Wang tiles can be used to tile the plane seamlessly with well spaced points. Kopf et
The shape matching method is a popular approach to simulate deformable objects in interactive app... more The shape matching method is a popular approach to simulate deformable objects in interactive applications due to its stability and simplicity. An important feature is that there is no need for a mesh since the method works on arbitrary local groups within a set of particles. A major drawback of shape matching is the fact that it is geometrically motivated and not derived from physical principles which makes calibration difficult. The fact that the method does not conserve volume can yield visual artifacts, e.g. when a tire is compressed but does not bulge.In this paper we present a new meshless simulation method that is related to shape matching but derived from continuous constitutive models. Volume conservation and stiffness can be specified with physical parameters. Further, if the elements of a tetrahedral mesh are used as groups, our method perfectly reproduces FEM based simulations.
We propose a hierarchical graph for learning physics and a novel way to handle obstacles. The fin... more We propose a hierarchical graph for learning physics and a novel way to handle obstacles. The finest level of the graph consist of the particles itself. Coarser levels consist of the cells of sparse grids with successively doubling cell sizes covering the volume occupied by the particles. The hierarchical structure allows for the information to propagate at great distance in a single message passing iteration. The novel obstacle handling allows the simulation to be obstacle aware without the need for ghost particles. We train the network to predict effective acceleration produced by multiple sub‐steps of 3D multi‐material material point method (MPM) simulation consisting of water, sand and snow with complex obstacles. Our network produces lower error, trains up to 7.0X faster and inferences up to 11.3X faster than [SGGP*20]. It is also, on average, about 3.7X faster compared to Taichi Elements simulation running on the same hardware in our tests.
Simulating large bodies of water in real time has been a research goal for a few decades. Existin... more Simulating large bodies of water in real time has been a research goal for a few decades. Existing procedural approaches like FFT-based simulations typically lack dynamic response like boundary-wave reflections or general body-fluid interactions like splashes or boat wakes. On the other side of the spectrum, existing dynamic Eulerian wave simulations suffer from high memory consumption required for adequate grid sizes in large scenes. Dynamic Lagrangian simulations like wave particles suffer from a potentially prohibitive particle count.
Abstract—We present a method designed to address some limitations of typical route map displays o... more Abstract—We present a method designed to address some limitations of typical route map displays of driving directions. The main goal of our system is to generate a printable version of a route map that shows the overview and detail views of the route within a single, consistent visual frame. Our proposed visualization provides a more intuitive spatial context than a simple list of turns. We present a novel multi-focus technique to achieve this goal, where the foci are defined by points-of-interest (POI) along the route. A detail lens that encapsulates the POI at a finer geospatial scale is created for each focus. The lenses are laid out on the map to avoid occlusion with the route and each other, and to optimally utilize the free space around the route. We define a set of layout metrics to evaluate the quality of a lens layout for a given route map visualization. We compare standard lens layout methods to our proposed method and demonstrate the effectiveness of our method in generat...
Closest point map Initial guess Final image Rasterization Variable stencil diffusion Figure 1: Di... more Closest point map Initial guess Final image Rasterization Variable stencil diffusion Figure 1: Diffusion curve rendering in our system. Analytical curves (left) are rasterized into a closest point map (distance map plus information about the closest curve point) and an initial guess image (middle). The initial guess is diffused by our variable stencil size solver, producing the final image (right).
Point clouds, as a form of Lagrangian representation, allow for powerful and flexible application... more Point clouds, as a form of Lagrangian representation, allow for powerful and flexible applications in a large number of computational disciplines. We propose a novel deep-learning method to learn stable and temporally coherent feature spaces for points clouds that change over time. We identify a set of inherent problems with these approaches: without knowledge of the time dimension, the inferred solutions can exhibit strong flickering, and easy solutions to suppress this flickering can result in undesirable local minima that manifest themselves as halo structures. We propose a novel temporal loss function that takes into account higher time derivatives of the point positions, and encourages mingling, i.e., to prevent the aforementioned halos. We combine these techniques in a super-resolution method with a truncation approach to flexibly adapt the size of the generated positions. We show that our method works for large, deforming point sets from different sources to demonstrate the f...
This paper is a report about a project practical course (“Projektpraktikum”) done at the Institut... more This paper is a report about a project practical course (“Projektpraktikum”) done at the Institute for Computer Graphics and Algorithms of the Vienna University of Technology. Advisor: Stefan Jeschke. The goal of this course was to implement a texture synthesis algorithm and analyze its performance and visual quality. Two papers form the theoretical foundation of this project: “Texture Optimization for Example-based Synthesis” by Kwatra et al [KEBK05] and “Patchmatch: A randomized Correspondence Algorithm for Structural Image Editing” by Barnes et al [BSFG09].
Shape Arrays allow propagating arrays of shapes that adapt the number of elements to the surround... more Shape Arrays allow propagating arrays of shapes that adapt the number of elements to the surrounding geometry with a single placement propagation. The choice between scaling or repeating shapes to fill the bounding box of a placement can be specified separately for the width and height dimensions. To implement shape arrays, we specify a minimum spacing between shapes and find the maximum number of shapes that can be placed along the width and height dimensions while respecting this minimum spacing. The spacing is then adjusted so that there is no space before the first and after the last shape in both dimensions.
Proceedings of the ACM SIGGRAPH / Eurographics Symposium on Computer Animation, 2017
Figure 1: Long range constraints propagate errors through large stacks or long chains instantaneo... more Figure 1: Long range constraints propagate errors through large stacks or long chains instantaneously and make it possible to simulate the depicted scenes with a small number of solver iterations.
In this paper, we introduce a novel scene representation for the visualization of large-scale poi... more In this paper, we introduce a novel scene representation for the visualization of large-scale point clouds accompanied by a set of high-resolution photographs. Many real-world applications deal with very densely sampled point-cloud data, which are augmented with photographs that often reveal lighting variations and inaccuracies in registration. Consequently, the high-quality representation of the captured data, i.e., both point clouds and photographs together, is a challenging and time-consuming task. We propose a two-phase approach, in which the first (preprocessing) phase generates multiple overlapping surface patches and handles the problem of seamless texture generation locally for each patch. The second phase stitches these patches at render-time to produce a high-quality visualization of the data. As a result of the proposed localization of the global texturing problem, our algorithm is more than an order of magnitude faster than equivalent mesh-based texturing techniques. Furthermore, since our preprocessing phase requires only a minor fraction of the whole dataset at once, we provide maximum flexibility when dealing with growing datasets.
IEEE Transactions on Visualization and Computer Graphics, 2014
In this paper, we introduce a novel scene representation for the visualization of large-scale poi... more In this paper, we introduce a novel scene representation for the visualization of large-scale point clouds accompanied by a set of high-resolution photographs. Many real-world applications deal with very densely sampled point-cloud data, which are augmented with photographs that often reveal lighting variations and inaccuracies in registration. Consequently, the high-quality representation of the captured data, i.e., both point clouds and photographs together, is a challenging and time-consuming task. We propose a two-phase approach, in which the first (preprocessing) phase generates multiple overlapping surface patches and handles the problem of seamless texture generation locally for each patch. The second phase stitches these patches at rendertime to produce a high-quality visualization of the data. As a result of the proposed localization of the global texturing problem, our algorithm is more than an order of magnitude faster than equivalent mesh-based texturing techniques. Furthermore, since our preprocessing phase requires only a minor fraction of the whole dataset at once, we provide maximum flexibility when dealing with growing datasets.
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Papers by Stefan Jeschke