Advances in geometry and reflectance acquisition (course notes)

Weinmann, Michael; Klein, Reinhard

doi:10.1145/2818143.2818165

Cited by 51 publications

(40 citation statements)

References 228 publications

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“…There is a recent survey by Schwartz et al [4] describing the options for measuring surface reflectance for computer graphics, including many details for the prototypes developed at the University of Bonn. Other older surveys are by Filip and Haindl [5], Weyrich et al [6] and Mueller et al [7], updated recently by Weinmann and Klein [8]. Most of the surface reflectance devices described in research papers, including those for measuring SVBRDF, utilise the Helmholtz reciprocity to halve the measurement time and sparsity of data.…”

Section: Related Workmentioning

confidence: 99%

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Lightdrum—Portable Light Stage for Accurate BTF Measurement on Site

Havran

Hošek

Němcová

et al. 2017

Sensors

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We propose a miniaturised light stage for measuring the bidirectional reflectance distribution function (BRDF) and the bidirectional texture function (BTF) of surfaces on site in real world application scenarios. The main principle of our lightweight BTF acquisition gantry is a compact hemispherical skeleton with cameras along the meridian and with light emitting diode (LED) modules shining light onto a sample surface. The proposed device is portable and achieves a high speed of measurement while maintaining high degree of accuracy. While the positions of the LEDs are fixed on the hemisphere, the cameras allow us to cover the range of the zenith angle from 0∘ to 75∘ and by rotating the cameras along the axis of the hemisphere we can cover all possible camera directions. This allows us to take measurements with almost the same quality as existing stationary BTF gantries. Two degrees of freedom can be set arbitrarily for measurements and the other two degrees of freedom are fixed, which provides a tradeoff between accuracy of measurements and practical applicability. Assuming that a measured sample is locally flat and spatially accessible, we can set the correct perpendicular direction against the measured sample by means of an auto-collimator prior to measuring. Further, we have designed and used a marker sticker method to allow for the easy rectification and alignment of acquired images during data processing. We show the results of our approach by images rendered for 36 measured material samples.

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Section: Related Workmentioning

confidence: 99%

“…The colourimetric calibration was carried out using the set of four colour calibration certified standards from Edmund Optics (red, green, blue, and yellow patch, the product number #56-079). The colourimetric calibration was carried out as described by Weinmann et al [8] and Schwartz et al [4]. …”

Section: Data Acquisition and Calibrationmentioning

confidence: 99%

Lightdrum—Portable Light Stage for Accurate BTF Measurement on Site

Havran

Hošek

Němcová

et al. 2017

Sensors

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“…We focus this overview on related work that shares some of the goals of our method: in-situ appearance acquisition, appearance modeling under natural lighting with unknown shape, recovering meso-structure, and exploiting chromatic cues for scene modeling. For a detailed overview of appearance modeling we refer to [DRS08,WK15].…”

Section: Related Workmentioning

confidence: 99%

On‐Site Example‐Based Material Appearance Acquisition

Lin

Peers

Ghosh

2019

Computer Graphics Forum

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We present a novel example‐based material appearance modeling method suitable for rapid digital content creation. Our method only requires a single HDR photograph of a homogeneous isotropic dielectric exemplar object under known natural illumination. While conventional methods for appearance modeling require prior knowledge on the object shape, our method does not, nor does it recover the shape explicitly, greatly simplifying on‐site appearance acquisition to a lightweight photography process suited for non‐expert users. As our central contribution, we propose a shape‐agnostic BRDF estimation procedure based on binary RGB profile matching. We also model the appearance of materials exhibiting a regular or stationary texture‐like appearance, by synthesizing appropriate mesostructure from the same input HDR photograph and a mesostructure exemplar with (roughly) similar features. We believe our lightweight method for on‐site shape‐agnostic appearance acquisition presents a suitable alternative for a variety of applications that require plausible “rapid‐appearance‐modeling”.

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“…For the introduction to this topic, we refer to the recent surveys by Weinmann et al . [WK15], Schwartz et al . [SSW*14], Haindl and Filip [HF13] and Dana [Dan16].…”

Section: Related Workmentioning

confidence: 99%

Increasing the Spatial Resolution of BTF Measurement with Scheimpflug Imaging

Havran

Hošek

Němcová

et al. 2019

Computer Graphics Forum

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We present an improved way of acquiring spatially varying surface reflectance represented by a bidirectional texture function (BTF). Planar BTF samples are measured as images at several inclination angles which puts constraints on the minimum depth of field of cameras used in the measurement instrument. For standard perspective imaging, we show that the size of a sample measured and the achievable spatial resolution are strongly interdependent and limited by diffraction at the lens' aperture. We provide a formula for this relationship. We overcome the issue of the required depth of field by using Scheimpflug imaging further enhanced by an anamorphic attachment. The proposed optics doubles the spatial resolution of images compared to standard perspective imaging optics. We built an instrument prototype with the proposed optics that is portable and allows for measurement on site. We show rendered images using the visual appearance measured by the instrument prototype.

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Advances in geometry and reflectance acquisition (course notes)

Cited by 51 publications

References 228 publications

Lightdrum—Portable Light Stage for Accurate BTF Measurement on Site

Lightdrum—Portable Light Stage for Accurate BTF Measurement on Site

On‐Site Example‐Based Material Appearance Acquisition

Increasing the Spatial Resolution of BTF Measurement with Scheimpflug Imaging

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