A Linear Variational System for Modelling From Curves

Andrews, James; Joshi, Prasad; Carr, Nathan

doi:10.1111/j.1467-8659.2011.01966.x

Cited by 19 publications

(22 citation statements)

References 26 publications

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“…In our implementation of biharmonic diffusion curves, we use a simple "sharp-profile" curve, "smooth-profile" curve paradigm for image designers to specify images. This is quite similar to the use of sharp-profile and smooth-profile curves in sketch-based surface modelling, such as in [Nealen et al 2007], [Joshi and Carr 2008] and [Andrews et al 2011]. Generally, a sharp-profile curve divides an image locally into independent left and right image regions, while a smoothprofile curve adjusts the colour variation of its (left and right) surrounding region.…”

Section: Specification Of Biharmonic Diffusion Curvesmentioning

confidence: 85%

Biharmonic diffusion curve images from boundary elements

et al. 2013

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Figure 1: Boundary element rendering of biharmonic diffusion curve images. From left to right: toys image; sharp-profile (solid) and smooth-profile (dotted) curves of the toys image, with thumbnail images below showing examples of the 4 building block segment fields; car image and pumpkin image. The above images are c CiSRA; the toys image is a CiSRA re-creation of a photograph taken by C. Concolato. AbstractThere is currently significant interest in freeform, curve-based authoring of graphic images. In particular, "diffusion curves" facilitate graphic image creation by allowing an image designer to specify naturalistic images by drawing curves and setting colour values along either side of those curves. Recently, extensions to diffusion curves based on the biharmonic equation have been proposed which provide smooth interpolation through specified colour values and allow image designers to specify colour gradient constraints at curves. We present a Boundary Element Method (BEM) for rendering diffusion curve images with smooth interpolation and gradient constraints, which generates a solved boundary element image representation. The diffusion curve image can be evaluated from the solved representation using a novel and efficient line-by-line approach. We also describe "curve-aware" upsampling, in which a full resolution diffusion curve image can be upsampled from a lower resolution image using formula evaluated corrections near curves. The BEM solved image representation is compact. It therefore offers advantages in scenarios where solved image representations are transmitted to devices for rendering and where PDE solving at the device is undesirable due to time or processing constraints.

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Section: Specification Of Biharmonic Diffusion Curvesmentioning

confidence: 85%

Biharmonic diffusion curve images from boundary elements

et al. 2013

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“…Some additional annotations [Gingold et al 2009;Olsen et al 2011] can be used to improve the shape's structure and topology. Similarly, other sketch-based methods have been proposed for producing 2.5D approximations instead of full 3D surfaces [Ono et al 2004;Chen et al 2005;Joshi and Carr 2008;Andrews et al 2011]. A common drawback of these approaches is that they require tedious specification of control curves with positional and directional constraints to produce the desired results.…”

Section: Related Workmentioning

confidence: 98%

“…The user can globally reduce smoothness by applying an arbitrary cross-section function to the inflation, however, it is currently not possible to control surface sharpness locally. To address this we plan to employ more advanced shape control approaches such as Cauchy constraints [Andrews et al 2011].…”

Section: Limitations and Future Workmentioning

confidence: 99%

Ink-and-ray

et al. 2014

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We present a new approach for generating global illumination renderings of hand-drawn characters using only a small set of simple annotations. Our system exploits the concept of bas-relief sculptures, making it possible to generate 3D proxies suitable for rendering without requiring side-views or extensive user input. We formulate an optimization process that automatically constructs approximate geometry sufficient to evoke the impression of a consistent 3D shape. The resulting renders provide the richer stylization capabilities of 3D global illumination while still retaining the 2D hand-drawn look-and-feel. We demonstrate our approach on a varied set of hand-drawn images and animations, showing that even in comparison to ground-truth renderings of full 3D objects, our bas-relief approximation is able to produce convincing global illumination effects, including self-shadowing, glossy reflections, and diffuse color bleeding. . 2014. Ink-and-ray: Bas-relief meshes for adding global illumination effects to hand-drawn characters.

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“…Vertices belonging to the open holes are then projected back to the global space. The remaining new interior vertices of the connections are then smoothed by solving a linear bi-Laplacian system [Andrews et al 2011] that is constrained by the positions and tangent vectors of the vertices that belong to the open holes.…”

Section: Strut Evaluationmentioning

confidence: 99%

Stress relief

et al. 2012

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a)b) c) d) Figure 1: A model of a dragon was first hollowed to reduce stress caused by its weight if held by the head (a). The stress decreased, but the neck had to be still thickened (b,c). The object was still too front heavy causing a twist deformation on the legs (c), that was eliminated by fixing the model to the pedestal by a strut (red) (d). These steps were done automatically by our system. AbstractThe use of 3D printing has rapidly expanded in the past couple of years. It is now possible to produce 3D-printed objects with exceptionally high fidelity and precision. However, although the quality of 3D printing has improved, both the time to print and the material costs have remained high. Moreover, there is no guarantee that a printed model is structurally sound. The printed product often does not survive cleaning, transportation, or handling, or it may even collapse under its own weight. We present a system that addresses this issue by providing automatic detection and correction of the problematic cases. The structural problems are detected by combining a lightweight structural analysis solver with 3D medial axis approximations. After areas with high structural stress are found, the model is corrected by combining three approaches: hollowing, thickening, and strut insertion. Both detection and correction steps are repeated until the problems have been eliminated. Our process is designed to create a model that is visually similar to the original model but possessing greater structural integrity.

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A Linear Variational System for Modelling From Curves

Cited by 19 publications

References 26 publications

Biharmonic diffusion curve images from boundary elements

Biharmonic diffusion curve images from boundary elements

Ink-and-ray

Stress relief

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