Results 1  10
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13
Physical Reproduction of Materials with Specified Subsurface Scattering
"... Figure 1: Left: photographs of slabs fabricated using a multimaterial 3D printer. We use a goaldriven optimization approach to find a volumetric arrangement of base material layers that best approximates an input heterogeneous subsurface scattering function. Right: the layering can also be applied ..."
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Cited by 23 (5 self)
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Figure 1: Left: photographs of slabs fabricated using a multimaterial 3D printer. We use a goaldriven optimization approach to find a volumetric arrangement of base material layers that best approximates an input heterogeneous subsurface scattering function. Right: the layering can also be applied to fabricate full 3D shapes. We investigate a complete pipeline for measuring, modeling, and fabricating objects with specified subsurface scattering behaviors. The process starts with measuring the scattering properties of a given set of base materials, determining their radial reflection and transmission profiles. We describe a mathematical model that predicts the profiles of different stackings of base materials, at arbitrary thicknesses. In an inverse process, we can then specify a desired reflection profile and compute a layered composite material that best approximates it. Our algorithm efficiently searches the space of possible combinations of base materials, pruning unsatisfactory states imposed by physical constraints. We validate our process by producing both homogeneous and heterogeneous composites fabricated using a multimaterial 3D printer. We demonstrate reproductions that have scattering properties approximating complex materials.
A Layered, Heterogeneous Reflectance Model for Acquiring and Rendering Human Skin
"... We introduce a layered, heterogeneous spectral reflectance model for human skin. The model captures the interscattering of light among layers, each of which may have an independent set of spatiallyvarying absorption and scattering parameters. For greater physical accuracy and control, we introduc ..."
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Cited by 22 (2 self)
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We introduce a layered, heterogeneous spectral reflectance model for human skin. The model captures the interscattering of light among layers, each of which may have an independent set of spatiallyvarying absorption and scattering parameters. For greater physical accuracy and control, we introduce an infinitesimally thin absorbing layer between scattering layers. To obtain parameters for our model, we use a novel acquisition method that begins with multispectral photographs. By using an inverse rendering technique, along with known chromophore spectra, we optimize for the best set of parameters for each pixel of a patch. Our method finds close matches to a wide variety of inputs with low residual error. We apply our model to faithfully reproduce the complex variations in skin pigmentation. This is in contrast to most previous work, which assumes that skin is homogeneous or composed of homogeneous layers. We demonstrate the accuracy and flexibility of our model by creating complex skin visual effects such as veins, tattoos, rashes, and freckles, which would be difficult to author using only albedo textures at the skin’s outer surface. Also, by varying the parameters to our model, we simulate effects from external forces, such as visible changes in blood flow within the skin due to external pressure.
Realtime Rendering of Heterogeneous Translucent Objects with Arbitrary Shapes
"... Figure 1: Rendering results at 22 frames persecond of the Stanford Thai Statue (157 K triangles) with our system. We present a realtime algorithm for rendering translucent objects of arbitrary shapes. We approximate the scattering of light inside the objects using the diffusion equation, which we ..."
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Cited by 6 (2 self)
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Figure 1: Rendering results at 22 frames persecond of the Stanford Thai Statue (157 K triangles) with our system. We present a realtime algorithm for rendering translucent objects of arbitrary shapes. We approximate the scattering of light inside the objects using the diffusion equation, which we solve onthefly using the GPU. Our algorithm is general enough to handle arbitrary geometry, heterogeneous materials, deformable objects and modifications of lighting, all in realtime. In a preprocessing step, we discretize the object into a regular 4connected structure (QuadGraph). Due to its regular connectivity, this structure is easily packed into a texture and stored on the GPU. At runtime, we use the QuadGraph stored on the GPU to solve the diffusion equation, in realtime, taking into account the varying input conditions: Incoming light, object material and geometry. We handle deformable objects, provided the deformation does not change the topological structure of the objects. 1.
Heterogeneous subsurface scattering using the finite element method
 IEEE Transactions on Visualization and Computer Graphics
, 2009
"... Abstract—Materials with visually important heterogeneous subsurface scattering, including marble, skin, leaves, and minerals, are common in the real world. However, general, accurate and efficient rendering of these materials is an open problem. In this paper, we describe a finite element (FE) solut ..."
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Cited by 6 (2 self)
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Abstract—Materials with visually important heterogeneous subsurface scattering, including marble, skin, leaves, and minerals, are common in the real world. However, general, accurate and efficient rendering of these materials is an open problem. In this paper, we describe a finite element (FE) solution of the heterogeneous diffusion equation (DE) that solves this problem. Our algorithm is the first to use the FE method to solve the difficult problem of heterogeneous subsurface rendering. To create our algorithm, we make two contributions. First, we correct previous work and derive an accurate and complete heterogeneous diffusion formulation. This formulation has two key elements: an accurate model of the reduced intensity (RI) source, the diffusive source boundary condition (DSBC), and its associated render query function. Second, we solve this formulation accurately and efficiently using the FE method. Using there results, we can render subsurface scattering with a simple four step algorithm. To demonstrate that our algorithm is simultaneously general, accurate and efficient, we test its performance on a series of difficult scenes. For a wide range of materials and geometry, it produces, in minutes, images that nearly match path traced references, that required hours. Index Terms—subsurface scattering, finite element method, diffusion equation, diffusive source boundary condition 1
AsConformalAsPossible Discrete Volumetric Mapping
"... In this paper, we tackle the problem of generalizing conformal maps to volumetric meshes. Current methods seek for harmonicity but unfortunately, no computational methods optimize conformality in the volumetric context. As it is proven that conformal maps do not exist for general volume transformati ..."
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Cited by 2 (0 self)
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In this paper, we tackle the problem of generalizing conformal maps to volumetric meshes. Current methods seek for harmonicity but unfortunately, no computational methods optimize conformality in the volumetric context. As it is proven that conformal maps do not exist for general volume transformations, we seek to optimize shape preservation with a generalization of the CauchyRiemann equations. Our algorithm is fast and easily adaptable to existing harmonic mapping methods. Compared to harmonic maps, results show improvements on both angular and volumetric energy measures at a cost below 1 % of total computations. The method extends well in any dimension and several research areas could benefit from our derivations of volumetric conformal optimization. (a) Harmonic (b) ACAP (c) Uniform scale Figure 1: An identical planar cut through a sphere with a small bump that is parameterized with (a) the Laplace operator, (b) the our operator, and (c) the uniform scale operator (ω=0.6125). 1.
A Practical Analytic Model for the Radiosity of Translucent Scenes
"... a) b) c) Figure 1: Interreflection and subsurface scattering are closely intertwined for scenes with translucent objects. The main contribution of this work is an analytic model of combining diffuse interreflection and subsurface scattering (see Figure 2). One bounce of specularities are added in ..."
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a) b) c) Figure 1: Interreflection and subsurface scattering are closely intertwined for scenes with translucent objects. The main contribution of this work is an analytic model of combining diffuse interreflection and subsurface scattering (see Figure 2). One bounce of specularities are added in a separate pass. a) Two translucent horses (63k polygons) illuminated by a point light source. The three zoomedin regions show that our method can capture both global illumination effects. b) The missing light transport component if only subsurface scattering is simulated. c) The same mesh rendered with a different lighting and viewing position. Our model supports interactive rendering of moving camera, scene relighting, and changing translucencies. Light propagation in scenes with translucent objects is hard to model efficiently for interactive applications. The interreflections between objects and their environments and the subsurface scattering through the materials intertwine to produce visual effects like color bleeding, light glows and soft shading. MonteCarlo based approaches have demonstrated impressive results but are computationally expensive, and faster approaches model either only interreflections or only subsurface scattering. In this paper, we present a simple analytic model that combines diffuse interreflections and isotropic subsurface scattering. Our approach extends the classical work in radiosity by including a subsurface scattering matrix that operates in conjunction with the traditional formfactor matrix. This subsurface scattering matrix can be constructed using analytic, measurementbased or simulationbased models and can capture both homogeneous and heterogeneous translucencies. Using a fast iterative solution to radiosity, we demonstrate scene relighting and dynamically varying object translucencies at near interactive rates.
Specular Reflection Single Scattering Shallow Scattering Deep Scattering Rendering Photograph
"... Figure 1: Layers of skin reflectance which are modeled by our technique and used to render faces for novel viewpoints and lighting. We present a practical method for modeling layered facial reflectance consisting of specular reflectance, single scattering, and shallow and deep subsurface scattering. ..."
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Figure 1: Layers of skin reflectance which are modeled by our technique and used to render faces for novel viewpoints and lighting. We present a practical method for modeling layered facial reflectance consisting of specular reflectance, single scattering, and shallow and deep subsurface scattering. We estimate parameters of appropriate reflectance models for each of these layers from just 20 photographs recorded in a few seconds from a single viewpoint. We extract spatiallyvarying specular reflectance and singlescattering parameters from polarizationdifference images under spherical and point source illumination. Next, we employ directindirect separation to decompose the remaining multiple scattering observed under crosspolarization into shallow and deep scattering components to model the light transport through multiple layers of skin. Finally, we match appropriate diffusion models to the extracted shallow and deep scattering components for different regions on the face. We validate our technique by comparing renderings of subjects to reference photographs recorded from novel viewpoints and under novel illumination conditions. 1
Photon Beam Diffusion: A Hybrid Monte Carlo Method for Subsurface Scattering
"... Figure 1: We solve the searchlight problem (a) using a Monte Carlo integration of dipoles distributed along either a normally incident (b) or oblique (c) beam. We can apply our hybrid approach to standard subsurface scattering (d) and also to more complex configurations using photon beams (e). We pr ..."
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Figure 1: We solve the searchlight problem (a) using a Monte Carlo integration of dipoles distributed along either a normally incident (b) or oblique (c) beam. We can apply our hybrid approach to standard subsurface scattering (d) and also to more complex configurations using photon beams (e). We present photon beam diffusion, an efficient numerical method for accurately rendering translucent materials. Our approach interprets incident light as a continuous beam of photons inside the material. Numerically integrating diffusion from such extended sources has long been assumed computationally prohibitive, leading to the ubiquitous singledepth dipole approximation and the recent analytic sumofGaussians approach employed by Quantized Diffusion. In this paper, we show that numerical integration of the extended beam is not only feasible, but provides increased speed, flexibility, numerical stability, and ease of implementation, while retaining the benefits of previous approaches. We leverage the improved diffusion model, but propose an efficient and numerically stable Monte Carlo integration scheme that gives equivalent results using only 3–5 samples instead of 20–60 Gaussians as in previous work. Our method can account for finite and multilayer materials, and additionally supports directional incident effects at surfaces. We also propose a novel diffuse exact singlescattering term which can be integrated in tandem with the multiscattering approximation. Our numerical approach furthermore allows us to easily correct inaccuracies of the diffusion model and even combine it with more general Monte Carlo rendering algorithms. We provide practical details necessary for efficient implementation, and demonstrate the versatility of our technique by incorporating it on top of several rendering algorithms in both research and production rendering systems.
JST, CREST
"... Figure 1: Examples of our method. The parameters for rendering clouds are estimated from the real photograph shown in the small inset at the top left corner of each image. The synthetic cumulonimbus clouds are rendered using the estimated parameters. Links: DL PDF 1 ..."
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Figure 1: Examples of our method. The parameters for rendering clouds are estimated from the real photograph shown in the small inset at the top left corner of each image. The synthetic cumulonimbus clouds are rendered using the estimated parameters. Links: DL PDF 1
Accurate Translucent Material Rendering under Spherical Gaussian Lights
"... In this paper we present a new algorithm for accurate rendering of translucent materials under Spherical Gaussian (SG) lights. Our algorithm builds upon the quantizeddiffusion BSSRDF model recently introduced in [dI11]. Our main contribution is an efficient algorithm for computing the integral of t ..."
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In this paper we present a new algorithm for accurate rendering of translucent materials under Spherical Gaussian (SG) lights. Our algorithm builds upon the quantizeddiffusion BSSRDF model recently introduced in [dI11]. Our main contribution is an efficient algorithm for computing the integral of the BSSRDF with an SG light. We incorporate both single and multiple scattering components. Our model improves upon previous work by accounting for the incident angle of each individual SG light. This leads to more accurate rendering results, notably elliptical profiles from oblique illumination. In contrast, most existing models only consider the total irradiance received from all lights, hence can only generate circular profiles. Experimental results show that our method is suitable for rendering of translucent materials under finitearea lights or environment lights that can be approximated by a small number of SGs.