Direct interaction with cultural heritage (CH) artefacts is frequently unavailable to visitors, offering an opportunity for HCI designers to explore integrating material aspects into digitally-mediated encounters with CH artefacts. We argue that a thorough understanding of the material experiences of CH artefacts can open a novel design space, enabling engaging and meaningful interactions with digital representations. Capitalising on this potential, we present a user study where we systematically explore the material experiences of historic pop-up and movable books. Our analysis identifies five key material qualities to inspire augmentation: fold-ability, slide-ability, tear-ability, age-ability, and print-ability. Highlighting how these material qualities can inspire novel interactions with their digital representations, we present two extended-reality (XR) prototypes of a CH book. With our work, we present HCI designers with a novel approach on designing CH experiences, firmly rooted in materiality, challenging the prevalent paradigms of ‘technology driven’ or ‘as-realistic-as-possible’ sensory experiences often found in CH-HCI.@en

Direct interaction with cultural heritage (CH) artefacts is frequently unavailable to visitors, offering an opportunity for HCI designers to explore integrating material aspects into digitally-mediated encounters with CH artefacts. We argue that a thorough understanding of the material experiences of CH artefacts can open a novel design space, enabling engaging and meaningful interactions with digital representations. Capitalising on this potential, we present a user study where we systematically explore the material experiences of historic pop-up and movable books. Our analysis identifies five key material qualities to inspire augmentation: fold-ability, slide-ability, tear-ability, age-ability, and print-ability. Highlighting how these material qualities can inspire novel interactions with their digital representations, we present two extended-reality (XR) prototypes of a CH book. With our work, we present HCI designers with a novel approach on designing CH experiences, firmly rooted in materiality, challenging the prevalent paradigms of 'technology-driven' or 'as-realistic-as-possible' sensory experiences often found in CH-HCI.

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This interactive textbook provides an educational resource into computational design for (industrial) designers. The book focusses on the use of computational design of products/artifacts at a human scale, which might be contrasted by the architectural/build environment scale – a domain which also extensively utilizes computational design principles and tools. Throughout the book, we make use of (commercial) computer-aided-design software, namely Rhinoceros®, and specifically the (build-in) module Grasshopper®. The lessons and knowledge base offered in this book focus on topics that are specifically relevant for and/or attuned to product design (scale), which are categorized in relation to its goal (e.g. design for personalized fit/comfort/aesthetics), by its means (e.g. design for digital fabrication), or for its role in the design process (e.g. for design exploration or design simulation). The book is intended for students both at bachelor and master level. As we believe in a learning-by-doing approach, we aimed for a hands-on, easy-to-get-started set of introductory lessons, which is complemented with a knowledge base. The introductory lessons do not assume any specific prior skills or knowledge (in general or with Rhino Grasshopper) to get started. Yet, (some) experience with computer-aided design (CAD), programming, data processing, and/or mathematics will likely be helpful to really delve into the more complex topics, such as those covered in the knowledge base. The book is currently used as course material in two courses taught at Industrial Design Engineering: “Prototyping with/for Digital Fabrication” (BSc level, part of the Minor Advanced Prototyping), and “Computational design for Digital Fabrication” (MSc level, Elective). The content in this book is in part based on course materials from the above-mentioned courses, which have been been taught to and applied by students with diverse (technical) backgrounds (e.g. industrial design, mechanical engineering, computer science, and electrical engineering). Other parts of the book are inspired by student (graduation) projects and/or follow from research activities by the various contributing authors.@en

BACKGROUND: A valid distribution of key anthropometric parameters among participants is often a perquisite of ergonomics research. OBJECTIVE: In this paper, we investigated the accuracy of self-reported stature and body mass of the population in the Netherlands. METHODS: Data from 4 experiments was synthesized where in each experiment, participants self-reported their stature and body mass prior to being measured, of which they were not notified before. RESULTS: Statistical analysis of 249 records indicated that on average, participants overreported their stature by 1.31 cm and underreported their mass by 1.45 kg. This is especially true for people with a BMI ≥ 25. CONCLUSION: Two models were proposed to adjust the self-reported stature and body mass for ergonomic researchers in a survey or recruitment. Limitations in using the models are highlighted as well.

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Personalized designs bring added value to the products and the users. Meanwhile, they also pose challenges to the product design process as each product differs. In this paper, with the focus on personalized fit, we present an overview as well as details of the personalized design process based on design practice. The general workflow of personalized product design is introduced first. Then different steps in the workflow such as human data/parameters acquisition, computational design, design for digital fabrication, and product evaluation are presented. Tools and methods that are often used in different steps in the process are also outlined where in human data acquisition, 3D scanning, and digital human models are addressed. For computational design, the use of computational thinking tools such as abstraction, decomposition, pattern recognition and algorithms are discussed. In design for digital fabrication, additive manufacturing methods (e.g. FDM), and their requirements on the design are highlighted. For product evaluation, both functional evaluation and usability evaluation are considered and the evaluation results can be the starting point of the next design iteration. Finally, several case studies are presented for a better understanding of the workflow, the importance of different steps in the workflow and the deviations in the approach regarding different contexts. In conclusion, we intend to provide designers a holistic view of the design process in designing personalized products as well as help practitioners trigger innovations regarding each step of the process.@en

Flavobacteria, which can be found in marine environments, are able to grow in highly organized colonies producing vivid iridescent colorations. While much is known about the biology of these organisms, their design potential as responsive media in user interfaces has not been explored. Our paper aims at bridging this gap by providing insights into the type, degree, and duration of change in Flavobacteria's expression, i.e., their living aesthetics. We present a tool to capture and characterize these changes concerning form, texture and iridescent color. To support the long-term study of their living aesthetics, we designed Flavorium. This bio-digital artifact provides the necessary habitat conditions for Flavobacteria to thrive for a month. Granting insights into the responsive behavior of this organism, this work presents a design space, vocabulary, and application concepts to inspire HCI and design scholars to investigate the complex temporal qualities of living media for future user interfaces.

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Acquiring an accurate 3D scan of the human hand is a challenging task, mainly due to the complicated geometry and the instability of the hand. In this paper, we present a low-cost photogrammetry-based scanner that is designed for scanning the human hand. The scanner has fifty modules, each has a Raspberry Pi with an 8-megapixels camera. They are uniformly positioned in two parallel frames and 96% of a hand surface can be viewed by at least 3 cameras. Using the timestamp method, we synchronize the shutters of the 50 cameras within the range of 80 ms to minimize the influence of the instability of the hand. Moreover, the scanner is easy to build with its modular design, and easy to operate with a laptop that is connected to the system by WiFi. Using a 3D printed prosthetic hand, we compared the 3D scanning accuracy of the proposed scanner with the Artec Spider® scanner. The mean absolute error between the two scans is 0.62 ± 0.28 mm. It is concluded that the proposed hand scanner can be used as a low-cost yet accurate tool in many applications, such as personalized product design.

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A high-fidelity digital representation of (part of) the human body is a key enabler for integrating humans in a digital twin. Among different parts of human body, building the model of the hand can be a challenging task due to the posture deviations among collected scans. In this article, we proposed a posture invariant statistical shape model (SSM) of the human hand based on 59 3D scans of human hands. First, the 3D scans were spatially aligned using a Möbius sphere-based algorithm. An articulated skeleton, which contains 20 bone segments and 16 joints, was embedded for each 3D scan. Then, all scans were aligned to the same posture using the skeleton and the linear blend skinning (LBS) algorithm. Three methods, i.e., principal component analysis (PCA), kernel-PCA (KPCA) with different kernel functions, and independent component analysis (ICA), were evaluated in the construction of the SSMs regarding the compactness, the generalization ability, and the specificity. The PCA-based SSM was selected, where 20 principal components were used as parameters for the model. Results of the leave-one-out validation indicate that the proposed model was able to fit a given 3D scan of the human hand at an accuracy of 1.21 ± 0.14 mm. Experiment results also indicated that the proposed SSM outperforms the SSM that was built on the scans without posture correction. It is concluded that the proposed posture correction approach can effectively improve the accuracy of the hand SSM and therefore enables its wide usage in human-integrated digital twin applications.

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Various imaging techniques are used to visualise issues regarding a painting’s appearance before, during and after conservation treatments, i.e. visible light photography (VIS) raking light photography (RAK), ultraviolet fluorescence photography (UVF) and reflectance transformation imaging (RTI). However, these techniques cannot always visualise and/or quantify conservation issues. This paper presents a new approach: colour, gloss, topography imaging (CGT). CGT’s applicability as a non-invasive tool for evaluating and documenting conservation treatments in comparison to VIS, UVF, RAK and RTI is discussed. Applying this to case studies with different conservation dilemmas illustrates the technique’s potential and drawbacks. CGT can visualise issues such as gloss variations, resulting from (previous) cleaning tests, (partial) varnish removal, and possibly dirt and material degradation. Furthermore, CGT can elucidate topographical issues such as bulging, and losses, and also visualise high-frequency surface variations (e.g. canvas weave and crack pattern). This results in an improvement of documenting a painting’s condition, and the evaluation of treatments and their effects on the visual appearance may be quantified. In conclusion, this research shows that CGT is able to better visualise texture, gloss and colour information than existing techniques like technical photography, facilitating a more precise documentation and localisation of previous and current conservation treatments.

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Fast, accurate and low-cost 3D scans are the key in designing personalized products. In this paper, using close-range photogrammetry technique, we aim at finding the “just enough” number of cameras and their spatial configurations for a full 3D reconstruction of the human hand. Given an object, we establish a mathematical model to describe the 3D constructible ratio based on the field of the view and the depth of field of each camera, as well as the visibility of each part of the object in the view of each camera. Furthermore, we introduce spatial constrains to arrange cameras along two rings for: 1) solving the problem of the large number of parameters in the unconstrained optimization, and 2) the feasibility and flexibility in the construction. Based on the found number of cameras and the spatial configuration of each camera, a prototype scanner was built to verify the effectiveness of the proposed method. The mean absolute error between the 3D scan of a 3D printed hand and its original CAD model was found to be 0.38mm, which is smaller than that (0.52mm) of using the conventional setup. Besides, the distribution of errors is smaller as well, which implicates a better full 3D reconstruction of the scanned hand.@en

High fidelity reproductions of paintings provide new opportunities to museums in preserving and providing access to cultural heritage. This paper presents an integrated system which is able to capture and fabricate color, topography and gloss of a painting, of which gloss capturing forms the most important contribution. A 3D imaging system, utilizing stereo imaging combined with fringe projection, is extended to capture spatially-varying gloss, based on the effect of specular reflectance polarization. The gloss is measured by sampling the specular reflection around Brewster’s angle, where these reflections are effectively polarized, and can be separated from the unpolarized, diffuse reflectance. Off-center gloss measurements are calibrated relative to the center measurement. Off-specular gloss measurements, following from local variation of the surface
normal, are masked based on the height map and corrected. Shadowed regions, caused by the 3D relief, are treated similarly. The area of a single capture is approximately 180x90mm at a resolution of 25x25μm. Aligned color, height, and gloss tiles are stitched together off-line, registering overlapping color regions. The resulting color, height and gloss maps are inputs for the poly-jet 3D printer. Two paintings were reproduced to verify the effectiveness and efficiency of the proposed system. One painting was scanned four times, consecutively rotated by 90 degrees, to evaluate the influence of the scanning system geometric configuration on the gloss measurement. Experimental results show that the method is sufficiently fast for practical application, i.e. to scan a whole painting within eight hours, during closing hours of a museum. The results can well be
used for the purpose of physical reproduction and other applications needing first-order estimates of the appearance (e.g. conservation diagnostics and condition reports). Our method to extend appearance scanning with gloss measurements is a valuable addition in the quest for realistic reproductions, in terms of its practical applicability - number of images needed for reconstruction and speed - and its perceptual added value, when added to color and topography reproduction.@en

2D coil design limits the use of wireless power transfer (WPT) in many products with freeform outer shapes. In this paper, enabled by 3D printed electronics, we propose a systematic approach to design and fabricate 3D coils for WPT. Based on the circular spiral and rectangular spiral patterns, 3D receiver and transmitter coils can be generated on an arbitrarily selected region of a product and its offset, respectively. Mathematical models are proposed to estimate the self-inductance and the mutual-inductance of the 3D arbitrarily shaped coils for 3D WPT. This leads to a new design approach of a 3D WPT system. Several sets of 3D printed WPT systems were designed, simulated, and prototyped to demonstrate the effectiveness of the proposed design approach as well as the mathematical models. The calculation speed of the proposed mathematical models is 30 times faster than the simulation, and compared with the measurement results, the calculation results have mean absolute errors of 2.63% and 4.45% regarding the self- and the mutual-inductance, where the simulation results have mean absolute errors of 1.20% and 2.38%, respectively. Measurements also indicate that with a 5V input, the prototypes are able to deliver 1-watt power at an efficiency ranging between 20.9% and 25.3%. It was concluded that the proposed approach is feasible and promising for designing and manufacturing WPT using 3D printed electronics.

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The appearance of a painting cannot solely be described by the depiction that it presents to the viewer. When viewing the artifact in real life, we find that the painted surface is in effect a three-dimensional landscape of paint. Paintings, “moveable, largely two-dimensional images created for the primary purpose of providing a visual experience”,1 can be created using a vast variety of materials on a range of supports. They are commonly built up as a complex stratigraphy of layers, generally consisting of a support, ground layer(s), one or multiple layers of (semi-) transparent paints, and in many cases a protective varnish layer. The current appearance of a painting is determined by the way a painter used and applied the materials, but also effects of aging, conservation and restoration treatments, which all continue to influence the physical state of a painting. Historically, cultural heritage (CH) reproductions were hand-crafted, and created for instance to disseminate or replace artworks, or to train in the skill of their creation. Also modern reproductions — or facsimiles — are still large hand-crafted, and for instance serve to provide access to (fragile) artworks or even complete (CH) sites, or to recreate their original appearance. Alternatively, reconstructions might reside only in the virtual domain. The continued development of digital imaging and digital fabrication technology (i.e. 3D printing) provides new opportunities for appearance reproduction, also suitable for application in the CH domain. If we want to replicate material appearance, we need to understand how (the appearance of) material is perceived. A material is, however, not observed directly, but has to be lighted, and via the light that is scattered by the material humans can perceive it. Appearance is therefore the light-material-confounded proximal stimulus for the human visual system (HVS). Even though we see, recognize and interact with a vast number of materials every day, and can effortlessly distinguish between them, it turns out that the perceptual mechanisms that underlie this, are still quite poorly understood, including linking individual appearance attributes to measurable and fabrication parameters. One of the consequences of this is that an integrated approach to (total) appearance reproduction, including color, topography/ texture/shape, gloss and transparency/translucency, is still lacking. @en

A seventeenth-century canvas painting is usually comprised of varnish and (translucent) paint layers on a substrate. A viewer’s perception of a work of art can be affected by changes in and damages to these layers. Crack formation in the multi-layered stratigraphy of the painting is visible in the surface topology. Furthermore, the impact of mechanical abrasion, (photo)chemical processes and treatments can affect the topography of the surface and thereby its appearance. New technological advancements in non-invasive imaging allow for the documentation and visualisation of a painting’s 3D shape across larger segments or even the complete surface. In this manuscript we compare three 3D scanning techniques, which have been used to capture the surface topology of Girl with a Pearl Earring by Johannes Vermeer (c. 1665): a painting in the collection of the Mauritshuis, the Hague. These three techniques are: multi-scale optical coherence tomography, 3D scanning based on fringe-encoded stereo imaging (at two resolutions), and 3D digital microscopy. Additionally, scans were made of a reference target and compared to 3D data obtained with white-light confocal profilometry. The 3D data sets were aligned using a scale-invariant template matching algorithm, and compared on their ability to visualise topographical details of interest. Also the merits and limitations for the individual imaging techniques are discussed in-depth. We find that the 3D digital microscopy and the multi-scale optical coherence tomography offer the highest measurement accuracy and precision. However, the small field-of-view of these techniques, makes them relatively slow and thereby less viable solutions for capturing larger (areas of) paintings. For Girl with a Pearl Earring we find that the 3D data provides an unparalleled insight into the surface features of this painting, specifically related to ‘moating’ around impasto, the effects of paint consolidation in earlier restoration campaigns and aging, through visualisation of the crack pattern. Furthermore, the data sets provide a starting point for future documentation and monitoring of the surface topology changes over time. These scans were carried out as part of the research project ‘The Girl in the Spotlight’.

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This work presents a halftoning technique to manufacture 3D objects with the appearance of continuous grayscale imagery for Fused Deposition Modeling (FDM) printers. While droplet-based dithering is a common halftoning technique, this is not applicable to FDM printing, since FDM builds up objects by extruding material in semi-continuous paths. The line-based halftoning principle called 'hatching' is applied to the line patterns naturally occuring in FDM prints, which are built up in a layer-by-layer fashion. The proposed halftoning technique isn't limited by the challenges existing techniques face; existing FDM coloring techniques greatly influence the surface geometry and deteriorate with surface slopes deviating from vertical or greatly influence the basic parameters of the printing process and thereby the structural properties of the resulting product. Furthermore, the proposed technique has little effect on printing time. Experiments on a dual-nozzle FDM printer show promising results. Future work is required to calibrate the perceived tone.@en

The aging of paintings is inevitable and over the years degradation occurs due to exposure to a variety of environmental influences. One of these degradations is craquelure, fracture patterns in the paint. 3D imaging techniques offer opportunities to capture the surface of a painting and these patterns at high resolution. In this paper we present a 3D scanner that is able to capture surface topography and color of oil paintings at high resolution utilizing fringe-encoded stereo imaging scanning system. The scanner is capable of automated capture of an area of 1x1m2, capturing a painting at a spatial resolution of 7 micron and a depth accuracy of 34 microns. Scanning at this resolution creates potential research opportunities for documentation and monitoring oil paintings under its environmental influences. A scan was made of 'Girl with a Pearl Earring' (c.1665), painted by Johannes Vermeer, which exhibits fine craquelure patterns. The scanner is able to capture the painting of 39x44.5 cm within 2 hours with a tile overlap of 25%. The results showed that the craquelure has more often a ridge-shaped profile instead of the expected inward valleys. The documentation of these variations in crack profiles create interesting paths for future research.@en

Being able to link captured material characteristics and fabricable material appearance attributes is important for creating life-like reproductions. In this paper we propose a method for gloss calibration, and an approach for gloss gamut mapping, as part of an integrated approach for color, topography and gloss reproduction. For gloss calibration, gloss calibration targets were printed in the primary printing colors (CMYK and White), with uniform gloss in equal distant gloss levels. These targets were scanned using the proposed gloss scanner. To create the gloss gamut map, a monotonic curve was fitted to the mean gloss scan values at different gloss levels. Analysis of fitted curves indicated that the gloss mapping is independent of the diffuse colors. As a case study, the painting ‘Fruit Still Life’ by Cornelis de Heem was scanned, and the measured gloss was mapped to printable gloss levels using the relation described by the fitted curve. The printed result shows good correspondence to the painting’s appearance, with clearly distinguishable gloss features for the in-gamut glass values.@en

In the past decade, wireless power transfer enabled many new applications. However, most designs of transmitter and receiver coils are 2D, which limits the possibilities of integrating them to more applications. In this paper, based on the Qi standard, we proposed a design of 3D coils by focusing on the 3D geometry of the coil, modelling, simulation and manufacturing. Using the 3D spiral transmitter coil and the receiver coil as an example, we present the mathematical model for WPT first. The performance of the model is then verified by FEM simulation. Three sets of 3D coils with different design parameters were prototyped by 3D printed electronics and measured against the model and the simulation results. Compared to the measurements, the model has average errors of 1.6%, 8.4% 8.5% regarding self-inductance, mutual-inductance and the coupling factor, where the simulation has average errors of 0.5%, 9.9% and 6.6%, respectively. Measurements also indicate that with a 5V input, the prototype is able to deliver 1-watt power at an average 20.5% efficiency without electromagnetic shielding. It was concluded that the proposed 3D coils designs are feasible and promising for WPT.@en

High fidelity reproductions of paintings provide new opportunities to museums in preserving and providing access to cultural heritage. This paper presents an integrated system which is able to capture and fabricate color, relief and gloss of a painting's surface, emphasizing on gloss capturing. To measure the spatially varying gloss, the specular reflection of the center of the scanned area is sampled at the Brewster angle, utilizing the effect of reflectance polarization at this angle. The off-center gloss measurements are corrected using the perpendicular and parallel reflectance coefficients, relative to the center measurement. Shadows in the gloss map, which are caused by 3D relief of the surface, are masked based on the height map and then filled by interpolating surrounding gloss information. The captured color image, height map and gloss map are inputs for the 3D printer. A painting "Two wrestling figures in the style of Van Gogh" was reproduced to verify the effectiveness and efficiency of the proposed system. Experiment results indicate that the proposed system gives accurate enough gloss measurement of the painting's surface for the purpose of gloss fabrication.@en