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- Front Matter: Volume 9398
- Rendering and Modeling
- Measuring
- Perception of Texture, Gloss, and Color in Materials: Joint Session with Conferences 9394 and 9398
- Appearance
- Reproduction
- Erratum
Front Matter: Volume 9398
Front Matter: Volume 9398
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This PDF file contains the front matter associated with SPIE Proceedings Volume 9398, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.
Rendering and Modeling
Imaging artwork in a studio environment for computer graphics rendering
Show abstract
When viewing a reproduction of a painting in textbooks and online, important visual information, including surface
texture, can be lost. Providing an experience to viewers that can convey some of this lost information without
significantly increasing the necessary equipment and training possessed by a typical studio photographer would enrich
education, documentation, conservation, and presentation of artwork for the public. A modified photometric stereo
technique coupled with the rendering software mental ray packaged with Maya® is presented as a means of capturing
surface normal maps and diffuse color information used in the rendering of realistic attributes of paintings. mental ray’s
ability to realistically render two different paintings with different gloss properties was evaluated by comparing the
proposed capture technique and a previously published technique that employs cross-polarization, demonstrating that
traditional imaging is a viable technique for generating input data for computer graphics rendering software.
Predictive rendering of composite materials: a multi-scale approach
T. Muller,
Patrick Callet,
F. da Graça,
et al.
Show abstract
Predictive rendering of material appearance means going deep into the understanding of the physical interaction between light and matter and how these interactions are perceived by the human brain. In this paper we describe our approach to predict the appearance of composite materials by relying on the multi-scale nature of the involved phenomena. Using recent works on physical modeling of complex materials, we show how to predict the aspect of a composite material based on its composition and its morphology. Specifically, we focus on the materials whose morphological structures are defined at several embedded scales. We rely on the assumption that when the inclusions in a composite material are smaller than the considered wavelength, the optical constants of the corresponding effective media can be computed by a homogenization process (or analytically for special cases) to be used into the Fresnel formulas.
Estimating reflectance property from multi-focus images by light field camera and its application
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In this paper, we propose a method to estimate the reflectance property from multi-focus images for light source reflected on the object. The blurred information of the light source on the surface is expected to be the practical method to estimate the reflectance property, even though various methods are proposed to estimate the reflectance property. However, the degree of the blurred information will be changed with the position of focus in the camera. Therefore, we introduce the light field camera which can change the position of the focus after the image are captured. In this research, we choose the image where the light source is focused on the object surface. Based on the blurred information of the focused light source, we estimated the reflectance property of the object. The estimated reflectance property is applied to inverse rendering for auto appearance valance.
Experiments with a low-cost system for computer graphics material model acquisition
Show abstract
We consider the design of an inexpensive system for acquiring material models for computer graphics rendering
applications in animation, games and conceptual design. To be useful in these applications a system must be able
to model a rich range of appearances in a computationally tractable form. The range of appearance of interest in
computer graphics includes materials that have spatially varying properties, directionality, small-scale geometric
structure, and subsurface scattering. To be computationally tractable, material models for graphics must be
compact, editable, and efficient to numerically evaluate for ray tracing importance sampling. To construct
appropriate models for a range of interesting materials, we take the approach of separating out directly and
indirectly scattered light using high spatial frequency patterns introduced by Nayar et al. in 2006. To acquire
the data at low cost, we use a set of Raspberry Pi computers and cameras clamped to miniature projectors.
We explore techniques to separate out surface and subsurface indirect lighting. This separation would allow
the fitting of simple, and so tractable, analytical models to features of the appearance model. The goal of the
system is to provide models for physically accurate renderings that are visually equivalent to viewing the original
physical materials.
BTF Potts compound texture model
Show abstract
This paper introduces a method for modeling mosaic-like textures using a multispectral parametric Bidirectional
Texture Function (BTF) compound Markov random field model (CMRF). The primary purpose of our synthetic
texture approach is to reproduce, compress, and enlarge a given measured texture image so that ideally both
natural and synthetic texture will be visually indiscernible, but the model can be easily applied for BFT material
editing. The CMRF model consist of several sub-models each having different characteristics along with an
underlying structure model which controls transitions between these sub models. The proposed model uses the
Potts random field for distributing local texture models in the form of analytically solvable wide-sense BTF
Markovian representation for single regions among the fields of a mosaic approximated by the Voronoi diagram.
The control field of the BTF-CMRF is generated by the Potts random field model build on top of the adjacency
graph of a measured mosaic. The compound random field synthesis combines the modified fast Swendsen-
Wang Markov Chain Monte Carlo sampling of the hierarchical Potts MRF part with the fast and analytical
synthesis of single regional BTF MRFs. The local texture regions (not necessarily continuous) are represented
by an analytical BTF model which consists of single factors modeled by the adaptive 3D causal auto-regressive
(3DCAR) random field model which can be analytically estimated as well as synthesized. The visual quality
of the resulting complex synthetic textures generally surpasses the outputs of the previously published simpler
non-compound BTF-MRF models.
Statistical analysis of bidirectional reflectance distribution functions
Show abstract
Bidirectional Reflectance Distribution Functions (BRDFs) are commonly employed in Computer Graphics and
Computer Vision to model opaque materials. On the one hand, a BRDF is a complex 4D function of both light
and view directions, which should ensure reciprocity and energy conservation laws. On the other hand, when
computing radiance reaching the eye from a surface point, the view direction is held fixed. In this respect, we
are only interested in a 2D BRDF slice that acts as a filter on the local environment lighting. The goal of our
work is to understand the statistical properties of such a filter as a function of viewing elevation. To this end,
we have conducted a study of measured BRDFs where we have computed statistical moments for each viewing
angle. We show that some moments are correlated together across dimensions and orders, while some others are
close to zero and may safely be discarded. Our study opens the way to novel applications such as moment-based
manipulation of measured BRDFs, material estimation and image-based material editing. It also puts empirical
and physically-based material models in a new perspective, by revealing their effect as view-dependent filters.
Principal component analysis for surface reflection components and structure in the facial image and synthesis of the facial image in various ages
Show abstract
In this paper, principal component analysis is applied to pigmentation distributions, surface reflectance components and
facial landmarks in the whole facial images to obtain feature values. Furthermore, the relationship between the obtained
feature vectors and age is estimated by multiple regression analysis to modulate facial images in woman of ages 10 to 70.
In our previous work, we analyzed only pigmentation distributions and the reproduced images looked younger than the
reproduced age by the subjective evaluation. We considered that this happened because we did not modulate the facial
structures and detailed surfaces such as wrinkles. By analyzing landmarks represented facial structures and surface
reflectance components, we analyzed the variation of facial structures and fine asperity distributions as well as
pigmentation distributions in the whole face. As a result, our method modulate the appearance of a face by changing age
more appropriately.
Extrapolation of bidirectional texture functions using texture synthesis guided by photometric normals
Show abstract
Numerous applications in computer graphics and beyond benefit from accurate models for the visual appearance of real-world materials. Data-driven models like photographically acquired bidirectional texture functions (BTFs) suffer from limited sample sizes enforced by the common assumption of far-field illumination. Several materials like leather, structured wallpapers or wood contain structural elements on scales not captured by typical BTF measurements. We propose a method extending recent research by Steinhausen et al. to extrapolate BTFs for large-scale material samples from a measured and compressed BTF for a small fraction of the material sample, guided by a set of constraints. We propose combining color constraints with surface descriptors similar to normal maps as part of the constraints guiding the extrapolation process. This helps narrowing down the search space for suitable ABRDFs per texel to a large extent. To acquire surface descriptors for nearly at materials, we build upon the idea of photometrically estimating normals. Inspired by recent work by Pan and Skala, we obtain images of the sample in four different rotations with an off-the-shelf flatbed scanner and derive surface curvature information from these. Furthermore, we simplify the extrapolation process by using a pixel-based texture synthesis scheme, reaching computational efficiency similar to texture optimization.
Measuring
Metrological issues related to BRDF measurements around the specular direction in the particular case of glossy surfaces
Show abstract
Among the complete bidirectional reflectance distribution function (BRDF), visual gloss is principally related to physical reflection characteristics located around the specular reflection direction. This particular part of the BRDF is usually referred to as the specular peak. A good starting point for the physical description of gloss could be to measure the reflection properties around this specular peak. Unfortunately, such a characterization is not trivial, since for glossy surfaces the width of the specular peak can become very narrow (typically a full width at half maximum inferior to 0.5° is encountered). In result, new BRDF measurement devices with a very small solid angle of detection are being introduced. Yet, differences in the optical design of BRDF measurement instruments engender different measurement results for the same specimen, complicating direct comparison of the measurement results. This issue is addressed in this paper. By way of example, BRDF measurement results of two samples, one being matte and the other one glossy, obtained by use of two high level goniospectrophotometers with a different optical design, are described. Important discrepancies in the results of the glossy sample are discussed. Finally, luminance maps obtained from renderings with the acquired BRDF data are presented, exemplifying the large visual differences that might be obtained. This stresses the metrological aspects that must be known for using BRDF data. Indeed, the comprehension of parameters affecting the measurement results is an inevitable step towards progress in the metrology of surface gloss, and thus towards a better metrology of appearance in general.
Upgrade of goniospectrophtometer GEFE for near-field scattering and fluorescence radiance measurements
Berta Bernad,
Alejandro Ferrero,
Alicia Pons,
et al.
Show abstract
The goniospectrophotometer GEFE, designed and developed at IO–CSIC (Instituto de Optica, Agencia Estatal Consejo Superior de Investigaciones Cientificas), was conceived to measure the spectral Bidirectional Reflectance Distribution Function (BRDF) at any pair of irradiation and detection directions. Although the potential of this instrument has largely been proved, it still required to be upgraded to deal with some important scattering features for the assessment of the appearance. Since it was not provided with a detector with spatial resolution, it simply could not measure spectrophotometric quantities to characterize texture through the Bidirectional Texture Function (BTF) or translucency through the more complex Bidirectional Scattering–Surface Reflectance Distribution Function (BSSRDF). Another requirement in the GEFE upgrading was to provide it with the capability of measuring fluorescence at different geometries, since some of the new pigments used in industry are fluorescent, which can have a non–negligible impact in the color of the product. Then, spectral resolution at irradiation and detection had to be available in GEFE. This paper describes the upgrading of the goniospectrophotometer GEFE, and its new capabilities through the presentation of sparkle and goniofluorescence measurements. In addition, the potential of the instrument to evaluate translucency by the measurement of the BSSRDF is briefly discussed.
Multiplexed acquisition of bidirectional texture functions for materials
Show abstract
The bidirectional texture function (BTF) has proven a valuable model for the representation of complex spatially varying material reflectance. Its image-based nature, however, makes material BTFs extremely cumbersome to acquire: in order to adequately sample high-frequency details, many thousands of images of a given material as seen and lit from different directions have to be obtained. Additionally, long exposure times are required to account for the wide dynamic range exhibited by the reflectance of many real-world materials.
We propose to significantly reduce the required exposure times by using illumination patterns instead of single light sources ("multiplexed illumination"). A BTF can then be produced by solving an appropriate linear system, exploiting the linearity of the superposition of light. Where necessary, we deal with signal-dependent noise by using a simple linear model derived from an existing database of material BTFs as a prior. We demonstrate the feasibility of our method for a number of real-world materials in a camera dome scenario.
An abridged goniometer for material appearance measurements
Show abstract
Goniospectrophotometers and custom laboratory setups are used to perform BRDF measurements of materials.
Those measurements can be used to improve the realism of previews of to be printed 3D objects, and for the
accurate representation of real objects in synthetic images. Unfortunately, the expensive nature of those devices
and the time required to measure each sample limit its use.
This paper presents a cost-effective, fast, and scalable solution to capture material appearance. This technique
is based on splitting the material information to capture into two main attributes: color and gloss. A
spectrophotometer is used to capture the color of a material, and the raw data of a linear sensor used in a
DOI-Gloss-Haze meter is used to obtain BRDF measurements, thus capturing the gloss appearance. Those
measurements can later be used to approximate the parameters of analytical BRDF models.
The technique is evaluated by comparing its results with high accuracy measurements of a goniospectrophotometer,
and the approximations obtained with the high accuracy measurements. A good approximation was
obtained when comparing the new technique to a goniospectrophotometer, except for a small underestimation
of the peak of the specular lobe on high gloss materials and the limitation to capture the specular lobe width of
broad specular lobes of low gloss materials.
New generation of Fourier optics instruments for fast multispectral BRDF characterization
Show abstract
A new generation of Fourier optics multispectral instruments that allow rapid full diffused or collimated beam spectral
BRDF measurements is presented. Light detection is made simultaneously at all angular locations including the
illumination direction. Backscattering effect in the fields of cosmetics and parasitic reflection of mobile displays are
reported as examples.
Color calibration of an RGB digital camera for the microscopic observation of highly specular materials
Show abstract
Color calibration of imaging devices has been previously studied in a varied number of situations where the materials observed have diffuse or only slightly specular surfaces. Most of the calibration methods available in the literature consist in using standard diffuse color charts in order to determine the mathematical operations necessary to transform the colors measured by the imaging device into the reference colors obtained from the target chart. Unfortunately, there are many problems, such as sensor saturation, that arise when using these methods to calibrate devices intended for the observation of highly specular samples, especially in the 0°:0° illumination/observation geometry used in microscopic imaging systems. In this paper, we explore several color calibration methods adapted for the observation of highly specular materials, and propose one method in particular in which we use colored filters and a calibrated mirror in order to obtain a set of specular colored samples. By using 72 samples for learning, we tested the different methods on 50 other samples and obtained, with the best one, an average CIE-DeltaE94 color difference of 1.93 units, which is a fairly good performance for color measurements at the microscopic scale.
An image-based multi-directional reflectance measurement setup for flexible objects
Show abstract
This paper presents an image-based method to measure reflectance of a homogeneous flexible object material (usually used in packaging). A point light source and a commercially available RGB camera is used to illuminate and measure the radiance reflected from the object surface in multiple reflection directions. By curving the flexible object onto a cylinder of known radius we are able to record radiance at multiple reflection angles in a faster way. In order to estimate the reflectance and to characterise the material, a spectralon reference tile is used. The spectralon tile is assumed to be homogenous and has near lambertain surface properties. Using Lambert’s cosine law, irradiance at a given point on the object surface is calculated. This information is then used to calculate a BRDF using Phong reflection model to describe the sample surface reflection properties. The measurement setup is described and discussed in this paper along with its use to estimate a BRDF for a given material/substrate. Results obtained indicate that the proposed image-based technique works well to measure light reflected at different planar angles and record information to estimate the BRDF of the sample materials that can be modelled using Phong reflection model. The object material properties, sample curvature and camera resolution decides the number of incident and reflection angles at which the bi-directional reflectance, or the material BRDF, can be estimated using this method.
Perception of Texture, Gloss, and Color in Materials: Joint Session with Conferences 9394 and 9398
Extended visual appearance texture features
Show abstract
The research purpose is to improve surface characterization based on what is perceived by human eye and on the 2006 CIE report. This report defines four headings under which possible measures might be made: color, gloss, translucency and texture. It is therefore important to define parameters able to discriminate surfaces, in accordance with the perception of human eye. Our starting point in assessing a surface is the measurement of its reflectance (acquisition of ABRDF for visual rendering), i.e. evaluate a set of images from different angles of lighting rather than a single image. The research question is how calculate, from this enhanced information, some discriminating parameters. We propose to use an image processing approach of texture that reflects spatial variations of pixel for translating changes in color, material and relief. From a set of images from different angles of light, we compute associated Haralick features for constructing new (extended) features, called Bidimensional Haralick Functions (BHF), and exploit them for discriminating surfaces. We propose another framework in three parts such as color, material and relief.
Goniochromatic difference between effect coatings: Is the whole more than the sum of its parts?
Show abstract
Special effect coatings have been increasingly used in many industries (e.g. automotive, plastics industry) over
the past two decades. The measurement of perceived color differences on such coatings cannot be done by means
of traditional color-difference formulas (e.g. CMC(l:c), CIEDE2000, AUDI2000) as they lack to consider distinct
optical properties such as coarseness, glint and goniochromatism. However, there is a need to ensure quality
and colorimetric accuracy when designing and processing special effect coatings. In this paper, we present a
psychophysical experiment intended to serve as a basis for future work on a new generation of color-difference
formula(s) for multiple viewing geometries (viewing and illumination angle). We are especially interested in
assessing whether judging under a single geometry can lead to different results as judging under several (two)
geometries, i.e. whether the sum is more than its part.
Visual comparison testing of automotive paint simulation
Show abstract
An experiment was performed to determine whether typical industrial automotive color paint comparisons made using real physical samples could also be carried out using a digital simulation displayed on a calibrated color television monitor. A special light booth, designed to facilitate evaluation of the car paint color with reflectance angle, was employed in both the real and virtual color comparisons. Paint samples were measured using a multi-angle spectrophotometer and were simulated using a commercially available software package. Subjects performed the test quicker using the computer graphic simulation, and results indicate that there is only a small difference between the decisions made using the light booth and the computer monitor. This outcome demonstrates the potential of employing simulations to replace some of the time consuming work with real physical samples that still characterizes material appearance work in industry.
Appearance
Goniometric and colorimetric properties of paints and varnish
Show abstract
The spectral reflectance of different samples of three different hues, (red, green, blue) with four different protective
varnishes was measured in 8/d condition and with a goniometer equipped with a spectrometer. The samples are
representative of hue and varnishes typically used in works of arts, the characterization was performed to test how the
different gloss finishing induced by transparent varnishes affect the spatial distribution of the luminance coefficient in
typical lighting arrangements for exposition of works of art. Nowadays the most used transparent protective varnishes
are matt or glossy, natural or synthetic. The choice within them is usually made looking at mechanical, chemical (also in
term of removal) and protective properties. Varnishes optical properties investigation on saturation and gloss alteration
of the perceived artifacts are not usually investigated. Expected results of this research include: analysis of influences on
color appearance of protective varnish according to the condition of illumination and observation, suggestion of new
additional criteria for varnish selection and lighting set up exposition and reliability of 8/d measurements condition, that
is a typical measurement set-up of portable instruments. Our results showed that natural varnishes are more able to
change the gloss of the surfaces than synthetic ones, because the shape and intensity of the specular peak for glossy and
matt natural varnish are very different. Both synthetic and natural varnishes have different behaviors at 30° or 60° light
incidences: at 30° of incidence all samples have smaller variations, while at 60° of incidence the variations are larger,
and for some samples the achromatic point is reached.
Goniochromatic and sparkle properties of effect pigmented samples in multidimensional configuration
Andreas Höpe,
Kai-Olaf Hauer,
Sven Teichert,
et al.
Show abstract
The effects of goniochromatism and sparkle are gaining more and more interest for surface refinement applications
driven by demanding requirements from such different branches as automotive, cosmetics, printing and packaging
industry. The common background and intention in all of these implementations is improvement of the visual appearance
of the related commercial products. Goniochromatic materials show strong angular-dependent reflection characteristics
and hence a color impression depending on the effective spatial arrangement of illumination and observation relative to
the surface of the artifact. Sparkle is a texture related effect giving a surface which is irradiated directionally, like direct
sun light, a bright glittering effect, similar to twinkling stars at the night sky. The prototype for this new effect is the
Xirallic® pigment of MERCK KGaA, Germany. The same pigment shows in diffuse irradiation, like on a cloudy day, a
different visual effect called graininess (coarseness) which appears as a granular structure of the surface. Both effects
were studied on especially manufactured samples of a dilution series in pigment concentration and a tonality series with
carbon black. The experiments were carried out with the robot-based gonioreflectometer and integrating sphere facilities
at Physikalisch-Technische Bundesanstalt (PTB) in multidimensional configurations of directional and diffuse
irradiation. The research is part of the European Metrology Research Program (EMRP), which is a metrology-focused
program of coordinated Research & Development (R&D) funded by the European Commission and participating
countries within the European Association of National Metrology Institutes (EURAMET). More information and
updated news concerning the project can be found on the xD-Reflect website http://www.xdreflect.eu/.
Anisotropic materials appearance analysis using ellipsoidal mirror
Jiří Filip,
Radomír Vávra
Show abstract
Many real-world materials exhibit significant changes in appearance when rotated along a surface normal. The
presence of this behavior is often referred to as visual anisotropy. Anisotropic appearance of spatially homogeneous materials is commonly characterized by a four-dimensional BRDF. Unfortunately, due to simplicity most
past research has been devoted to three dimensional isotropic BRDFs. In this paper, we introduce an innovative,
fast, and inexpensive image-based approach to detect the extent of anisotropy, its main axes and width of corresponding anisotropic highlights. The method does not rely on any moving parts and uses only an off-the-shelf
ellipsoidal reflector with a compact camera. We analyze our findings with a material microgeometry scan, and
present how results correspond to the microstructure of individual threads in a particular fabric. We show that
knowledge of a material’s anisotropic behavior can be effectively used in order to design a material-dependent
sampling pattern so as the material’s BRDF could be measured much more precisely in the same amount of time
using a common gonioreflectometer.
Changing the color of textiles with realistic visual rendering
Show abstract
Fast and easy preview of a fabric without having to produce samples would be very profitable for textile designers, but
remains a technological challenge. As a first step towards this objective, we study the possibility of making images of a
real sample, and changing virtually the colors of its yarns while preserving the shine and shadow texture. We consider
two types of fabrics: Jacquard weave fabrics made of polyester warp and weft yarns of different colors, and satin ribbons
made of polyester and metallic yarns. For the Jacquard fabric, we make a color picture with a scanner on a sample in
which the yarns have contrasted colors, threshold this image in order to distinguish the pixels corresponding to each
yarn, and accordingly modify their hue and chroma values. This method is simple to operate but do not enable to
simulate the angle-dependent shine. A second method, tested on the satin ribbon made of black polyester and achromatic
metallic yarns, is based on polarized imaging. We analyze the polarization state of the reflected light which is different
for dielectric and metallic materials illuminated by polarized light. We then add a fixed color value to the pixels
representing the polyester yarns and modify the hue and chroma of the pixels representing the metallic yarns. This was
performed for many incident angles of light, in order to render the twinkling effect displayed by these ribbons. We could
verify through a few samples that the simulated previews reproduce real pictures with visually acceptable accuracy.
Reproduction
3D printed glass: surface finish and bulk properties as a function of the printing process
Show abstract
It is impossible to print glass directly from a melt, layer by layer. Glass is not only very sensitive to temperature gradients between different layers but also to the cooling process. To achieve a glass state the melt, has to be cooled rapidly to avoid crystallization of the material and then annealed to remove cooling induced stress. In 3D-printing of glass the objects are shaped at room temperature and then fired. The material properties of the final objects are crucially dependent on the frit size of the glass powder used during shaping, the chemical formula of the binder and the firing procedure. For frit sizes below 250 μm, we seem to find a constant volume of pores of less than 5%. Decreasing frit size leads to an increase in the number of pores which then leads to an increase of opacity. The two different binders, 2- hydroxyethyl cellulose and carboxymethylcellulose sodium salt, generate very different porosities. The porosity of samples with 2-hydroxyethyl cellulose is similar to frit-only samples, whereas carboxymethylcellulose sodium salt creates a glass foam. The surface finish is determined by the material the glass comes into contact with during firing.
Color-managed 3D printing with highly translucent printing materials
Can Ates Arikan,
Alan Brunton,
Tejas Madan Tanksale,
et al.
Show abstract
Many 3D printing applications require the reproduction of an object's color in addition to its shape. One
3D printing technology, called multi-jetting (or poly-jetting), allows full color 3D reproductions by arranging
multiple colored materials (UV curing photo-polymers) on a droplet level in a single object. One property of
such printing materials is their high translucency posing new challenges for characterizing such 3D printers to
create ICC profiles.
In this paper, we will first describe the whole color-managed 3D printing workflow and will then focus
on measuring the colors of highly translucent printing materials. We will show that measurements made by
spectrophotometers used in the graphic arts industry are systematically biased towards lower reflection. We will
then propose a trichromatic camera-based approach for measuring such colors. Error rates obtained in comparison
with spectroradiometric measurements for the same viewing conditions are within the interinstrument-variability
of hand-held spectrophotometers used in graphic arts.
Towards gloss control in fine art reproduction
Show abstract
The studies regarding fine art reproduction mainly focus on the accuracy of colour and the recreation of surface texture
properties. Since reflection properties other than colour are neglected, important details of the artwork are lost. For
instance, gloss properties, often characteristic to painters and particular movements in the history of art, are not well
reproduced. The inadequate reproduction of the different gloss levels of a piece of fine art leads to a specular reflection
mismatch in printed copies with respect to the original works that affects the perceptual quality of the printout. We used
different print parameters of a 3D high resolution printing setup to control the gloss level on a printout locally. Our
method can be used to control gloss automatically and in crucial applications such as fine art reproduction.
Exploring the bronzing effect at the surface of ink layers
Show abstract
We investigate the optical phenomenon responsible for the colored shine that sometimes appears at the surface of ink
layers in the specular direction, often called bronzing or gloss differential. It seems to come from the wavelength-dependent
refractive index of the ink, which induces a wavelength-dependent reflectance of the ink-air interface. Our
experiments on cyan and magenta inkjet inks confirm this theory. Complex refractive indices can be obtained from
measurements of the spectral reflectance and transmittance of a transparency film coated with the ink. We propose a
correction of the classical Clapper-Yule model in order to include the colored gloss in the prediction of the spectral
reflectance of an inked paper. We also explored effects of scattering by the micrometric or nanometric roughness of the
ink surface. The micrometric roughness, easy to model with a geometrical optics model, can predict the spreading of the
colored gloss over a large cone. Electromagnetic models accounting for the effect of the nanometric roughness of the
surface also predict the attenuation of short wavelengths observed under collimated illumination.
Controlling colour-printed gloss by varnish-halftones
Show abstract
Printing appearance effects beyond colour - such as gloss - is an active research topic in the scope of multi-layer printing (2.5D or 3D printing). Such techniques may enable a perceptually more accurate reproduction of optical material properties and are required to avoid appearance related artefacts sometimes observed in regular colour printing - such as bronzing and differential gloss. In addition to technical challenges of printing such effects, a perceptual space that describes the related visual attributes is crucial; particularly to define perceptually meaningful tolerances and for appearance gamut mapping. In this paper, we focus on spatially-varying gloss created by varnish-halftones. This enables us to print specular gloss effects covering a large portion of the NCS gloss scale from full matte to high gloss. We then conduct a psychophysical experiment to find the relationship between measured specular gloss and a perceptually uniform gloss scale. Our results show that this relationship can be well described by a power function according to Stevens Power Law.
Reproducing oil paint gloss in print for the purpose of creating reproductions of Old Masters
Willemijn S. Elkhuizen,
Boris A. J. Lenseigne,
Teun Baar,
et al.
Show abstract
In the field of Fine Art reproduction, 3D scanning plus 3D printing, combined with dedicated software, now allows to
capture and reproduce the color and texture of oil paintings. However, for life-like reproduction of the material
appearance of such paintings, the typical gloss and translucency must also be included, which is currently not the case.
The aim of this paper is to elaborate on the challenges and results of capturing and reproducing oil paint gloss (next to
texture and color) using a scanning and printing system. A sample was hand-made using oil paint and acrylic varnish,
and its gloss was then reproduced. A gloss map of the painted sample was acquired using a high end DLSR camera and a
simple acquisition protocol. Next, Océ High Resolution 3D printing technology was used to create samples with spatially
varying gloss. For this, two different strategies were combined: (1) multilevel half-toning of the colors was used to
reproduce matte color layers, and (2) varnish was half-toned on top in increasing coverage to recreate increasing gloss
levels. This paper presents an overview of the state-of-the-art literature in gloss reproduction and perception, our process
of reproduction as well as the visual evaluation of the quality of the created reproduction.
3D printing awareness: the future of making things
Show abstract
The advent of 3D printing is giving us new production opportunities but is creating new economic and social assets. In
the paper we will analyze the new conditions we will live in.
The current industrial production scenario will be analyzed to see how it works and how 3D printing is being introduced
into it: where the traditional production comes from and how it actually works, from the historical, technological, social
and economic point of view, including transports of materials and products.
This asset is being “polluted” and possibly transformed by 3D printing: what is it, how it works, but most important, how
this technology is transforming our personal approach to industrial products.
This technological innovation will transform our lives, possibly even more than how movable type printing did: we will
see the opportunities offered to adopt this innovation not only for our everyday life, but also looking forward for
environmental issues, (e)commerce reorganization and social quality improvement.
In the final part we will also see what will be the keys to open a new kind of developing path, where technology will take
an important part, what relationship with it humans will have, and which will be the keys to succeed in this challenge,
identifying in knowledge, awareness and culture of innovation those keys.
Erratum
An image-based multi-directional reflectance measurement setup for flexible objects (Erratum)
Show abstract
Publisher’s Note: This paper, originally published on 13 March 2015, was replaced with a corrected/revised version on 6 August 2019. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.