Browsing by Author "Mould, David"

Now showing 1 - 5 of 5
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    Distribution Update of Deformable Patches for Texture Synthesis on the Free Surface of Fluids
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Gagnon, jonathan; Guzmán, Julián E.; Vervondel, Valentin; Dagenais, François; Mould, David; Paquette, Eric; Lee, Jehee and Theobalt, Christian and Wetzstein, Gordon
    We propose an approach for temporally coherent patch-based texture synthesis on the free surface of fluids. Our approach is applied as a post-process, using the surface and velocity field from any fluid simulator. We apply the texture from the exemplar through multiple local mesh patches fitted to the surface and mapped to the exemplar. Our patches are constructed from the fluid free surface by taking a subsection of the free surface mesh. As such, they are initially very well adapted to the fluid's surface, and can later deform according to the free surface velocity field, allowing a greater ability to represent surface motion than rigid or 2D grid-based patches. From one frame to the next, the patch centers and surrounding patch vertices are advected according to the velocity field. We seek to maintain a Poisson disk distribution of patches, and following advection, the Poisson disk criterion determines where to add new patches and which patches should e flagged for removal. The removal considers the local number of patches: in regions containing too many patches, we accelerate the temporal removal. This reduces the number of patches while still meeting the Poisson disk criterion. Reducing areas with too many patches speeds up the computation and avoids patch-blending artifacts. The final step of our approach creates the overall texture in an atlas where each texel is computed from the patches using a contrast-preserving blending function. Our tests show that the approach works well on free surfaces undergoing significant deformation and topological changes. Furthermore, we show that our approach provides good results for many fluid simulation scenarios, and with many texture exemplars. We also confirm that the optical flow from the resulting texture matches the fluid velocity field. Overall, our approach compares favorably against recent work in this area.
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    Implicit Representation of Inscribed Volumes
    (ACM, 2018) Sahbaei, Parto; Mould, David; Wyvill, Brian; Aydın, Tunç and Sýkora, Daniel
    We present an implicit approach for constructing smooth isolated or interconnected 3-D inscribed volumes which can be employed for volumetric modeling of various kinds of spongy or porous structures, such as volcanic rocks, pumice stones, Cancellus bones, liquid or dry foam, radiolarians, cheese, and other similar materials. The inscribed volumes can be represented in their normal or positive forms to model natural pebbles or pearls, or in their inverted or negative forms to be used in porous structures, but regardless of their types, their smoothness and sizes are controlled by the user without losing the consistency of the shapes. We introduce two techniques for blending and creating interconnections between these inscribed volumes to achieve a great flexibility to adapt our approach to different types of porous structures, whether they are regular or irregular. We begin with a set of convex polytopes such as 3-D Voronoi diagram cells and compute inscribed volumes bounded by the cells. The cells can be irregular in shape, scale, and topology, and this irregularity transfers to the inscribed volumes, producing natural-looking spongy structures. Describing the inscribed volumes with implicit functions gives us a freedom to exploit volumetric surface combinations and deformations operations effortlessly.
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    Irregular Pebble Mosaics with Sub-Pebble Detail
    (The Eurographics Association, 2019) Javid, Ali Sattari; Doyle, Lars; Mould, David; Kaplan, Craig S. and Forbes, Angus and DiVerdi, Stephen
    Pebble mosaics convey images through an irregular tiling of rounded pebbles. Past work used relatively uniform tile sizes. We show how to create detailed representations of input photographs in a pebble mosaic style; we first create pebble shapes through a variant of k-means, then compute sub-pebble detail with textured, two-tone pebbles.We use a custom distance function to ensure that pebble sizes adapt to local detail and orient to local feature directions, for an overall effect of high fidelity to the input photograph despite the constraints of the pebble style.
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    Patch Erosion for Deformable Lapped Textures on 3D Fluids
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Gagnon, Jonathan; Guzmán, Julián E.; Mould, David; Paquette, Eric; Mitra, Niloy and Viola, Ivan
    We propose an approach to synthesise a texture on an animated fluid free surface using a distortion metric combined with a feature map. Our approach is applied as a post-process to a fluid simulation. We advect deformable patches to move the texture along the fluid flow. The patches are covering the whole surface every frame of the animation in an overlapping fashion. Using lapped textures combined with deformable patches, we successfully remove blending artifact and rigid artifact seen in previous methods. We remain faithful to the texture exemplar by removing distorted patch texels using a patch erosion process. The patch erosion is based on a feature map provided together with the exemplar as inputs to our approach. The erosion favors removing texels toward the boundary of the patch as well as texels corresponding to more distorted regions of the patch. Where texels are removed leaving a gap on the surface, we add new patches below existing ones. The result is an animated texture following the velocity field of the fluid. We compared our results with recent work and our results show that our approach removes ghosting and temporal fading artifacts.
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    Stipple Removal in Extreme-tone Regions
    (The Eurographics Association, 2019) Azami, Rosa; Doyle, Lars; Mould, David; Kaplan, Craig S. and Forbes, Angus and DiVerdi, Stephen
    Conventional tone-preserving stippling struggles with extreme-tone regions. Dark regions require immense quantities of stipples, while light regions become littered with stipples that are distracting and, because of their low density, cannot communicate any image features that may be present. We propose a method to address these problems, augmenting existing stippling methods. We will cover dark regions with solid polygons rather than stipples; in light areas, we both preprocess the image to prevent stipple placement in the very lightest areas and postprocess the stipple distribution to remove stipples that contribute little to the image structure. Our modified stipple images have better visual quality than the originals despite using fewer stipples.