Welcome to the Realistic Graphics and Imaging group in the Department of Computing at Imperial College London. We conduct research in realistic computer graphics spanning acquisition, modeling and rendering of real world materials, objects and scenes, as well as imaging for graphics and vision including computational photography and illumination. We are affiliated to the Visual Information Processing section within DOC.

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Projects

  • Acquiring axially-symmetric transparent objects using single-view transmission imaging

    We propose a novel, practical solution for high quality reconstruction of axially-symmetric transparent objects such as glasses, tumblers, goblets, carafes, etc., using single-view transmission imaging of a few patterns emitted from a background LCD panel. Our approach employs inverse ray tracing to reconstruct both completely symmetric as well as more complex n-fold symmetric everyday transparent objects.

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  • Acquiring Spatially Varying Appearance of Printed Holographic Surfaces

    We present two novel and complimentary approaches to measure diffraction effects in commonly found planar spatially varying holographic surfaces. Such holographic surfaces are usually manufactured with one dimensional diffraction gratings that are varying in periodicity and orientation over an entire sample in order to produce a wide range of diffraction effects such as gradients and kinematic (rotational) effects. Our proposed methods estimate these two parameters and allow an accurate reproduction of these effects in real-time.

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  • Diffuse-Specular Separation using Binary Spherical Gradient Illumination

    We introduce a novel method for view-independent diffuse-specular separation of albedo and photometric normals without requiring polarization using binary spherical gradient illumination. The method does not impose restrictions on viewpoints and requires fewer photographs for multiview acquisition than polarized spherical
    gradient illumination.

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  • Efficient surface diffraction renderings with Chebyshev approximations

    We propose an efficient method for reproducing diffraction colours on natural surfaces with complex nanostructures that can be represented as height-fields. Our method employs Chebyshev approximations to accurately model view-dependent iridescences for such a surface into its spectral bidirectional reflectance distribution function (BRDF). As main contribution, our method significantly reduces the runtime memory footprint from precomputed lookup tables without compromising photorealism.

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  • Image-Based Relighting using Room Lighting Basis

    We present a novel and practical approach for image-based relighting that employs the lights available in a regular room to acquire the reflectance field of an object. We achieve plausible results for diffuse and glossy objects that are qualitatively similar to results produced with dense sampling of the reflectance field including using a light stage. We believe our approach can be applied for practical relighting applications with general studio lighting.

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  • Mobile Surface Reflectometry

    We propose two novel setups for acquiring spatially varying surface reflectance properties of planar samples using mobile devices. Our first setup employs free-form handheld acquisition with the back camera-flash pair on a typical mobile device and is suitable for rough specular samples. Ours second setup, suitable for highly specular samples, employs the LCD panel on a tablet as an extended illumination source.

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  • Multispectral Light Stage

    We have built a multispectral LED sphere (light stage) consisting of 168 RGB and color temperature controllable white LED lamps, respectively. The LED sphere has a 2.5 meter diameter steel structure, and employs off-the-shelf programmable LED lamps.

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  • Polarization imaging reflectometry in the wild

    We present a novel approach for on-site acquisition of surface reflectance for planar, spatially-varying samples in uncontrolled outdoor environments. We exploit the naturally occurring linear polarization of incident illumination and employ polarization imaging from two near orthogonal views close to the Brewster angle of incidence for reflectance estimation.

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  • Practical acquisition and rendering of diffraction effects in surface reflectance

    We propose two novel contributions for measurement based rendering of diffraction effects in surface reflectance of planar homogeneous diffractive materials. Firstly for commonly manufactured materials, we propose a practical data-driven rendering technique and a measurement approach to efficiently render complex diffraction effects in real-time. Our measurement step simply involves photographing a planar diffractive sample illuminated with an LED flash and a spectral filter. Secondly, for sharp specular samples, we propose a novel method for practical measurement of the underlying diffraction grating using out-of-focus “bokeh” photography of the specular highlight.

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  • Practical acquisition of translucent liquids using polarized transmission imaging

    We present a practical method to acquire optical properties of translucent liquids for realistic rendering using polarized transmission imaging of light through a liquid volume in a transparent container.

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