Jeppe Revall Frisvad

Jeppe Revall Frisvad
Technical University of Denmark | DTU · Department of Applied Mathematics and Computer Science

PhD, MSc(Eng)

About

67
Publications
9,605
Reads
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551
Citations
Introduction
Jeppe Revall Frisvad is an associate professor at the Technical University of Denmark (DTU). He received an M.Sc.(Eng.) degree in applied mathematics (2004) and a Ph.D. degree in computer graphics (2008) from DTU. His research interests are mainly material appearance modeling, realistic rendering, and light scattering. As a highlight, his work includes development of the first diffusion dipole for subsurface scattering based on ray sources.
Additional affiliations
March 2011 - present
Technical University of Denmark
Position
  • Professor (Associate)
May 2008 - February 2011
Technical University of Denmark
Position
  • Professor (Assistant)
January 2008 - April 2008
Microsoft
Position
  • Developer
Education
November 2004 - May 2008
Technical University of Denmark
Field of study
  • Computer Graphics
September 1999 - October 2004
Technical University of Denmark
Field of study
  • Applied Mathematics

Publications

Publications (67)
Article
Image denoising based on deep learning has become a powerful tool to accelerate Monte Carlo rendering. Deep learning techniques can produce smooth images using a low sample count. Unfortunately, existing deep learning methods are biased and do not converge to the correct solution as the number of samples increase. In this paper, we propose a progre...
Article
Full-text available
Spectral X-ray computed tomography (SCT) is an emerging method for non-destructive imaging of the inner structure of materials. Compared with the conventional X-ray CT, this technique provides spectral photon energy resolution in a finite number of energy channels, adding a new dimension to the reconstructed volumes and images. While this mitigates...
Article
Full-text available
To study the shape of objects using geometric morphometrics, landmarks are oftentimes collected digitally from a 3D scanned model. The expert may annotate landmarks using software that visualizes the 3D model on a flat screen, and interaction is achieved with a mouse and a keyboard. However, landmark annotation of a 3D model on a 2D display is a te...
Preprint
We tackle the problem of generating novel-view images from collections of 2D images showing refractive and reflective objects. Current solutions assume opaque or transparent light transport along straight paths following the emission-absorption model. Instead, we optimize for a field of 3D-varying Index of Refraction (IoR) and trace light through i...
Article
Full-text available
When 3D scanning objects, the objective is usually to obtain a continuous surface. However, most surface scanning methods, such as structured light scanning, yield a point cloud. Obtaining a continuous surface from a point cloud requires a subsequent surface reconstruction step, which is directly affected by any error from the computation of the po...
Article
Full-text available
The bidirectional reflectance distribution function (BRDF) and the bidirectional scattering - surface reflectance distribution function (BSSRDF), which relate radiance at the surface to irradiance and radiant flux, respectively, are regarded as the most fundamental scattering quantities used to determine the reflectance of objects. However, for mat...
Article
We propose a method for direct comparison of rendered images with a corresponding photograph in order to analyze the optical properties of physical objects and test the appropriateness of appearance models. To this end, we provide a practical method for aligning a known object and a point-like light source with the configuration observed in a photo...
Article
Most models for bidirectional surface scattering by arbitrary explicitly defined microgeometry are either based on geometric optics and include multiple scattering but no diffraction effects or based on wave optics and include diffraction but no multiple scattering effects. The few exceptions to this tendency are based on rigorous solution of Maxwe...
Article
The outset of realistic rendering is a desire to reproduce the appearance of the real world. Rendering techniques therefore operate at a scale corresponding to the size of objects that we observe with our naked eyes. At the same time, rendering techniques must be able to deal with objects of nearly arbitrary shapes and materials. These requirements...
Conference Paper
Interactive 3D modeling in VR is both aided by immersive 3D input and hampered by model disjunct, tool-based or selection-action user interfaces. We propose a direct, signifier-based approach to the popular interactive technique of creating 3D models through a sequence of extrusion operations. Motivated by handles and signifiers that communicate th...
Article
Full-text available
Digital light processing stereolithography is a promising technique for 3D printing. However, it offers little control over the surface appearance of the printed object. The printing process is typically layered, which leads to aliasing artefacts that affect surface appearance. An antialiasing option is to use greyscale pixel values in the layer im...
Article
Micro-structured surfaces are increasingly being used on parts and products to embed functional properties that could be optical, electrical, thermal, or likewise. In this work, directional optical properties were achieved on plastic with a microstructure composed of a close array of ridges, defined by a constant width and by the angle with respect...
Article
This paper offers background and perspective on a little-known memoir by Ludvig Lorenz on light scattering by spheres, which was published in Danish in 1890. It is a companion to an English translation of the memoir appearing separately. Apart from introducing Lorenz and some of his contributions to optics and electrodynamics, the paper focuses on...
Preprint
The most prevalent routine for camera calibration is based on the detection of well-defined feature points on a purpose-made calibration artifact. These could be checkerboard saddle points, circles, rings or triangles, often printed on a planar structure. The feature points are first detected and then used in a nonlinear optimization to estimate th...
Chapter
We present a data-driven proof of concept method for image-based semantic segmentation of objects based on their materials. We target materials with complex radiometric appearances, such as reflective and refractive materials, as their detection is particularly challenging in many modern vision systems. Specifically, we select glass, chrome, plasti...
Chapter
The measurement of a bidirectional reflectance distribution function (BRDF) requires a purpose-built instrument. We ease this requirement by presenting a relative method for measuring a BRDF using a multipurpose robotic arm. Our focus is on the alignment of the system to perform accurate camera positioning and orientation. We use a six degrees of f...
Article
The functional properties of micro-structured surfaces have gained increasing interest thanks to many applications such as wetting, adhesion, thermal and/or electrical conductivity. In this study, directional optical properties, i.e. contrast between two regions of a surface, were achieved with an anisotropic microstructure composed of a close arra...
Article
In absorbing media, electromagnetic plane waves are most often inhomogeneous. Existing solutions for the scattering of an inhomogeneous plane wave by a spherical particle provide no explicit expressions for the scattering components. In addition, current analytical solutions require evaluation of the complex hypergeometric function F12 for every te...
Article
Full-text available
Spectral CT is an emerging imaging method that involves using recently developed energy discriminating photon counting detectors. This technique enables measurements at isolated high-energy ranges, in which the dominating undergoing interaction between the X-ray and the sample is the incoherent scattering. The scattered radiation causes a loss of c...
Conference Paper
This is a virtual reality (VR) painting application that enables the user to paint on 3D models with real measured materials, much like in the physical world. A scanned physical object can be imported into the VR application, and the user can paint on the surface of the object with a virtual hand-controlled paint brush. The user is presented with s...
Article
Transparent objects require acquisition modalities that are very different from the ones used for objects with more diffuse reflectance properties. Digitizing a scene where objects must be acquired with different modalities requires scene reassembly after reconstruction of the object surfaces. This reassembly of a scene that was picked apart for sc...
Conference Paper
Interactive ray tracing applications running on commodity hardware can suffer from objectionable temporal artifacts due to a low sample count. We introduce stable ray tracing, a technique that improves temporal stability without the over-blurring and ghosting artifacts typical of temporal post-processing filters. Our technique is based on sample re...
Conference Paper
This paper explores potential use cases for using augmented reality (AR) as a tool to operate industrial machines. As a baseline we use an additive manufacturing system, more commonly known as a 3D printer. We implement novel augmented interfaces and controls using readily available open source frameworks and low cost hardware. Our results show tha...
Article
Full-text available
Existing techniques for interactive rendering of deformable translucent objects can accurately compute diffuse but not directional subsurface scattering effects. It is currently a common practice to gain efficiency by storing maps of transmitted irradiance. This is, however, not efficient if we need to store elements of irradiance from specific dir...
Article
Springer International Publishing AG 2017. This paper explores potential use cases for using augmented reality (AR) as a tool to operate industrial machines. As a baseline we use an additive manufacturing system, more commonly known as a 3D printer. We implement novel augmented interfaces and controls using readily available open source frameworks...
Conference Paper
In this paper we present a color design pipeline for 3D printed or additively manufactured parts. We demonstrate how to characterize and calibrate a commercial printer and how to obtain its forward and backward color transformation models. We present results from our assistive color design tool, allowing for colorimetric accurate prints and visuali...
Article
Full-text available
Hair is typically modeled and rendered using either explicitly defined hair strand geometry or a volume texture of hair densities. Taken each on their own, these two hair representations have difficulties in the case of animal fur as it consists of very dense and thin undercoat hairs in combination with coarse guard hairs. Explicit hair strand geom...
Article
Diffuse reflectance measurements are useful for noninvasive inspection of optical properties such as reduced scattering and absorption coefficients. Spectroscopic analysis of these optical properties can be used for particle sizing. Systems based on optical fiber probes are commonly employed, but their low spatial resolution limits their validity r...
Conference Paper
Full-text available
VirtualTable is a projection augmented reality installation where users are engaged in an interactive tower defense game. The installation runs continuously and is designed to attract people to a table, which the game is projected onto. Any number of players can join the game for an optional period of time. The goal is to prevent the virtual styliz...
Conference Paper
In this positional paper, we discuss the potential benefits of using appearance models in additive manufacturing, metal casting, wind turbine blade production, and 3D content acquisition. Current state of the art in acquisition and rendering of appearance cannot easily be used for quality assurance in these areas. The common denominator is the need...
Article
The quality of a dairy product is largely determined by its microstructure which also affects its optical properties. In this way, an assessment of the optical properties during production may be part of a feedback system for ensuring the quality of the production process. In this paper, we investigate the use of a camera based measurement technolo...
Article
Rendering translucent materials using Monte Carlo ray tracing is computationally expensive due to a large number of subsurface scattering events. Faster approaches are based on analytical models derived from diffusion theory. While such analytical models are efficient, they miss out on some translucency effects in the rendered result. We present an...
Article
We present a photon splatting technique which reduces noise and blur in the rendering of caustics. Blurring of illumination edges is an inherent problem in photon splatting, as each photon is unaware of its neighbours when being splatted. This means that the splat size is usually based on heuristics rather than knowledge of the local flux density....
Conference Paper
Pond of Illusion is a mixed reality installation where a virtual space (the pond) is injected between two real spaces. The users are in either of the real spaces, and they can see each other through windows in the virtual space as illustrated in Figure 1(left). The installation attracts people to a large display in either of the real spaces by allo...
Conference Paper
Light scattering in turbid media can be related to the microstructure of media. Thus, light scattering can potentially be used for process control of products where the structure is a key component. However process control requires robust and sensitive input data to function properly. In this study we investigate different decomposition methods for...
Article
Photon-density estimation techniques are a popular choice for simulating light transport in scenes with complicated geometry and materials. This class of algorithms can be used to accurately simulate inter-reflections, caustics, color bleeding, scattering in participating media, and subsurface scattering. Since its introduction, photon-density esti...
Article
I present two tools that save the computation of a dot product and a reciprocal square root in operations that are used frequently in the core of many rendering programs. The first tool is a formula for rotating a direction sampled around the z-axis to a direction sampled around an arbitrary unit vector. This is useful in Monte Carlo rendering tech...
Conference Paper
Full-text available
We present a technique for real-time rendering of teeth with no need for computational or artistic preprocessing. Teeth constitute a translucent material consisting of several layers; a highly scattering mate-rial (dentine) beneath a semitransparent layer (enamel) with a transpar-ent coating (saliva). In this study we examine how light interacts wi...
Article
Computer graphics systems today are able to produce highly realistic images. The realism has reached a level where an observer has difficulties telling whether an image is real or synthetic. The exception is when we try to compute a picture of a scene that really exists and compare the result to a photograph of the real scene. In this direct compar...
Article
Rayleigh scattering is used frequently in Monte Carlo simulation of multiple scattering. The Rayleigh phase function is quite simple, and one might expect that it should be simple to importance sample it efficiently. However, there seems to be no one good way of sampling it in the literature. This paper provides the details of several different tec...
Conference Paper
Full-text available
We present a novel photon mapping algorithm for animations. We extend our previous work on photon differentials [12] with time differentials. The result is a first order model of photon cones in space an time that effectively reduces the number of required photons per frame as well as efficiently reduces temporal aliasing without any need for in-be...
Article
Full-text available
The finite frame rate also used in computer animated films is cause of adverse temporal aliasing effects. Most noticeable of these is a stroboscopic effect that is seen as intermittent movement of fast moving illumination. This effect can be mitigated using non-zero shutter times, effectively, constituting a temporal smoothing of rapidly changing i...
Article
The refractive index of freezing brine is important in order to, for example, estimate oceanic scattering as sea ice develops. Previously, no simple continuous expression was available for estimating the refractive index of brine at subzero temperatures. I show that extrapolation of the empirical formula for the refractive index of seawater by Quan...
Article
Glare is a consequence of light scattered within the human eye when looking at bright light sources. This effect can be exploited for tone mapping since adding glare to the depiction of high-dynamic range (HDR) imagery on a low-dynamic range (LDR) medium can dramatically increase perceived contrast. Even though most, if not all, subjects report per...
Conference Paper
Full-text available
At the moment the noise functions available in a graphics programmer's toolbox are either slow to compute or they involve grid-line artifacts making them of lower quality. In this paper we present a real-time noise computation with no grid-line artifacts or other regularity problems. In other words, we put a new tool in the box that computes fast h...
Article
This paper introduces a theoretical model for computing the scattering properties of participating media and translucent materials. The model takes as input a description of the components of a medium and computes all the parameters necessary to render it. These parameters are the extinction and scattering coefficients, the phase function, and the...
Article
This paper introduces a theoretical model for computing the scattering properties of participating media and translucent materials. The model takes as input a description of the components of a medium and computes all the parameters necessary to render it. These parameters are the extinction and scattering coefficients, the phase function, and the...
Conference Paper
Full-text available
A number of popular global illumination algorithms uses density estimation to approximate indirect illumination. The density es- timate is performed on finite points - particles - generated by a stochastic sampling of the scene. In the course of the sampling, particles, representing light, are stochastically emitted from the light sources and refle...
Conference Paper
Full-text available
Developments in the graphics discipline called realistic image syn- thesis are in many ways related to the historical development of the- ories of light. And theories of light will probably continue to inspire the ongoing search for realism in graphics. To nurture this inspira- tion, we present the first in-depth, source-based historical study that...
Article
Full-text available
The current technology such as semantic web and ontology allows everyone to build rapidly vast knowledge bases for a specific domain. A development of story animation knowledge bases is presented. The knowledge bases are used to produce movie animation ...
Article
This paper introduces a theoretical model for computing the scattering properties of participating media and translucent materials. The model takes as input a description of the components of a medium and computes all the parameters necessary to render it. These parameters are the extinction and scattering coefficients, the phase function, and the...
Conference Paper
Full-text available
A novel method for real-time simulation of indirect illumination is presented in this paper. The method, which we call direct radiance mapping (DRM), is based on basal radiance calculations and does not impose any restrictions on scene geometry or dynamics. This makes the method tractable for real-time rendering of arbitrary dynamic environments an...
Conference Paper
Full-text available
This paper concerns real-time rendering of thin semi-transparent objects. An object in this category could be a piece of cloth, eg. a curtain. Semi-transparent objects are visualized most correctly using volume rendering techniques. In general such techniques are, however, intractable for real-time applications. Surface rendering is more efficient,...
Article
Adapting games to the miniature screens and limited process- ing power of mobile phones is quite a challenge. To accom- modate these technical limitations, mobile games are often two- dimensional (2D), tile-based, and seen from above. Such games rarely present much creativity with respect to dynamic lighting. Textures are merely plastered onto the...
Article
To obtain unpredictable social interaction between autonomous agents in real-time en- vironments, we present a simple method for logic-based knowledge exchange. A method which is able to form new knowledge rather than do simple exchange of particular rules found in predetermined rule sets. The applicability of our concept is demonstrated through a...
Article
The notion of abduction has found its usage within a wide variety of AI elds. Computing abduc- tive solutions has, however, shown to be highly in- tractable in logic programming. To avoid this in- tractability we present a new approach to logic- based abduction; through the geometrical view of data employed in array-based logic we embrace ab- ducti...
Article
Full-text available
Digital prototyping has revolutionised the automotive industry by providing designers and engineers with digital models of their products that enable virtual product design, visualisation, and simulation [1]. However, digital prototyping does not exist in the food industry as the colloidal nature of most foods make them much more challenging to vis...

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Projects

Projects (4)
Project
Research activities in sensors and 3D geometric and radiometric modeling in relation to the cyber-physical 3D ecosystem. https://eco3d.compute.dtu.dk/
Project
EURAMET EMPIR joint research project (JRP) co-funded by EU Horizon 2020 and participating states. https://bxdiff.cmi.cz/
Project
This is an Innovative Training Network (ITN) funded by the EU Horizon 2020 research programme. https://www.appears-itn.eu/