Conference Paper

A Dual Light Stage.

DOI: 10.2312/EGWR/EGSR05/091-098 Conference: Proceedings of the Eurographics Symposium on Rendering Techniques, Konstanz, Germany, June 29 - July 1, 2005
Source: DBLP


We present a technique for capturing high-resolution 4D reflectance fields using the reciprocity property of light transport. In our technique we place the object inside a diffuse spherical shell and scan a laser across its surface. For each incident ray, the object scatters a pattern of light onto the inner surface of the sphere, and we photograph the resulting radiance from the sphere's interior using a camera with a fisheye lens. Because of reciprocity, the image of the inside of the sphere corresponds to the reflectance function of the surface point illuminated by the laser, that is, the color that point would appear to a camera along the laser ray when the object is lit from each direction on the surface of the sphere. The measured reflectance functions allow the object to be photorealistically rendered from the laser's viewpoint under arbitrary directional illumination conditions. Since each captured re- flectance function is a high-resolution image, our data reproduces sharp specular reflections and self-shadowing more accurately than previous approaches. We demonstrate our technique by scanning objects with a wide range of reflectance properties and show accurate renderings of the objects under novel illumination conditions.

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    • "Helmholtz reciprocity tells us that the BRDF is symmetric in its incoming and outgoing directions ( f (θ i , φ i , θ o , φ o ) = f (θ o , φ o , θ i , φ i )), and isotropy implies that there is no preferred azimuthal orientation or 'grain' to the surface (( f (θ i , φ i , θ o , φ o ) = f (θ o , θ i , |φ o − φ i |)). In computer vision, these properties have been exploited for surface reconstruction [11] [18], and since they effectively reduce the BRDF domain, they have also been used extensively for image-based rendering in computer graphics (e.g., [7] [14]). "
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    ABSTRACT: A set of images of a Lambertian surface under varying lighting directions defines its shape up to a three-parameter Generalized Bas-Relief (GBR) ambiguity. In this paper, we examine this ambiguity in the context of surfaces having an additive non-Lambertian reflectance component, and we show that the GBR ambiguity is resolved by any non-Lambertian reflectance function that is isotropic and spatially invariant. The key observation is that each point on a curved surface under directional illumination is a member of a family of points that are in isotropic or reciprocal configurations. We show that the GBR can be resolved in closed form by identifying members of these families in two or more images. Based on this idea, we present an algorithm for recovering full Euclidean geometry from a set of uncalibrated photometric stereo images, and we evaluate it empirically on a number of examples.
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    • "This rough specular surface will ensure that incident illumination from the projector is projected in a small solid angle in the direction of the focus point, but without reflecting too much illumination towards other points on the mirror (which would cause undesirable interreflection). A diffuse coating, such as used in the Dual Light Stage [10], would exhibit a larger degree of interreflection relative to the albedo of "
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    ABSTRACT: We present a novel acquisition device to capture high resolution 4D re- flectance fields of real scenes. The device consists of a concave hemispher- ical surface coated with a rough specular paint and a digital video projector with afish-eye lens positioned near the center of the hemisphere. The scene is placed near the projector, also near the center, and photographed from a fixed vantage point. The projector projects a high-resolution image of incident illu- mination which is reflected by the rough hemispherical surface to become the illumination on the scene. We demonstrate the utility of this device by cap- turing a high resolution hemispherical reflectance field of a specular object which would be difficult to capture using previous acquisition techniques.
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    • "Erlangen, Germany, November 16–18, 2005 A light stage [4] [10] samples the reflectance field of objects for a single view point, as illuminated by a set of point light sources with fixed spacing. In order to record highly specular or transparent objects the spacing between the light source has to be reduced , i.e. the resolution of the reflectance field has to be increased drastically [14] [8]. Relighting based on these data sets is limited to distant light sources, e.g. "
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    ABSTRACT: In this paper we address the problem of relight-ing with sparsely sampled reflectance fields. We present a technique that approximates the correct result of relighting from intermediate light source positions. The acquisition of reflectance fields is a time consuming process, and typically the sampling resolution in the light source positions is rather lim-ited. As a consequence, smoothly moving high-lights and shadows due to relighting with a mov-ing light source are hard to generate. Using light source interpolation, densely sampled reflectance fields can be simulated, enabling relighting with area light sources and smooth animation of high-lights and shadows. Using light source interpolation we can relight with arbitrarily sampled 4D incident light fields from complex or near-by light sources.
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