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Now showing 1 - 4 of 4
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    crdbrd: Shape Fabrication by Sliding Planar Slices
    (The Eurographics Association and John Wiley and Sons Ltd., 2012) Hildebrand, Kristian; Bickel, Bernd; Alexa, Marc; P. Cignoni and T. Ertl
    We introduce an algorithm and representation for fabricating 3D shape abstractions using mutually intersecting planar cut-outs. The planes have prefabricated slits at their intersections and are assembled by sliding them together. Often such abstractions are used as a sculptural art form or in architecture and are colloquially called 'cardboard sculptures'. Based on an analysis of construction rules, we propose an extended binary space partitioning tree as an efficient representation of such cardboard models which allows us to quickly evaluate the feasibility of newly added planar elements. The complexity of insertion order quickly increases with the number of planar elements and manual analysis becomes intractable. We provide tools for generating cardboard sculptures with guaranteed constructibility. In combination with a simple optimization and sampling strategy for new elements, planar shape abstraction models can be designed by iteratively adding elements. As an output, we obtain a fabrication plan that can be printed or sent to a laser cutter. We demonstrate the complete process by designing and fabricating cardboard models of various well-known 3D shapes.
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    SHADOWPIX: Multiple Images from Self Shadowing
    (The Eurographics Association and John Wiley and Sons Ltd., 2012) Bermano, Amit; Baran, Ilya; Alexa, Marc; Matusik, Wojciech; P. Cignoni and T. Ertl
    SHADOWPIX are white surfaces that display several prescribed images formed by the self-shadowing of the surface when lit from certain directions. The effect is surprising and not commonly seen in the real world. We present algorithms for constructing SHADOWPIX that allow up to four images to be embedded in a single surface. SHADOWPIX can produce a variety of unusual effects depending on the embedded images: moving the light can animate or relight the object in the image, or three colored lights may be used to produce a single colored image. SHADOWPIX are easy to manufacture using a 3D printer and we present photographs, videos, and renderings demonstrating these effects.
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    Approximating Free-form Geometry with Height Fields for Manufacturing
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Herholz, Philipp; Matusik, Wojciech; Alexa, Marc; Olga Sorkine-Hornung and Michael Wimmer
    We consider the problem of manufacturing free-form geometry with classical manufacturing techniques, such as mold casting or 3-axis milling. We determine a set of constraints that are necessary for manufacturability and then decompose and, if necessary, deform the shape to satisfy the constraints per segment. We show that many objects can be generated from a small number of (mold-)pieces if slight deformations are acceptable. We provide examples of actual molds and the resulting manufactured objects.
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    Isosurface Extraction for Signed Distance Functions using Power Diagrams
    (The Eurographics Association and John Wiley & Sons Ltd., 2025) Kohlbrenner, Maximilian; Alexa, Marc; Bousseau, Adrien; Day, Angela
    Contouring an implicit function typically considers function values in the vicinity of the desired level set, only. In a recent string of works, Sellán at al. have demonstrated that signed distance values contain useful information also if they are further away from the surface. This can be exploited to increase the resolution and amount of detail in surface reconstruction from signed distance values. We argue that the right tool for this analysis is a regular triangulation of the distance samples, with the weights chosen based on the distance values. The resulting triangulation is better suited for reconstructing the surface than a standard Delaunay triangulation of the samples. Moreover, the dual power diagram encodes the envelope enclosing the surface, consisting of spherical caps. We discuss how this information can be exploited for reconstructing the surface. In particular, the approach based on regular triangulations lends itself well to refining the sample set. Refining the sample set based on the power diagram outperforms other reconstruction methods relative to the sample count.