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Now showing 1 - 10 of 10
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    Reactive Gaze during Locomotion in Natural Environments
    (The Eurographics Association and John Wiley & Sons Ltd., 2024) Melgaré, Julia K.; Rohmer, Damien; Musse, Soraia R.; Cani, Marie-Paule; Skouras, Melina; Wang, He
    Animating gaze behavior is crucial for creating believable virtual characters, providing insights into their perception and interaction with the environment. In this paper, we present an efficient yet natural-looking gaze animation model applicable to real-time walking characters exploring natural environments. We address the challenge of dynamic gaze adaptation by combining findings from neuroscience with a data-driven saliency model. Specifically, our model determines gaze focus by considering the character's locomotion, environment stimuli, and terrain conditions. Our model is compatible with both automatic navigation through pre-defined character trajectories and user-guided interactive locomotion, and can be configured according to the desired degree of visual exploration of the environment. Our perceptual evaluation shows that our solution significantly improves the state-of-the-art saliency-based gaze animation with respect to the character's apparent awareness of the environment, the naturalness of the motion, and the elements to which it pays attention.
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    Unerosion: Simulating Terrain Evolution Back in Time
    (The Eurographics Association and John Wiley & Sons Ltd., 2024) Yang, Zhanyu; Cordonnier, Guillaume; Cani, Marie-Paule; Perrenoud, Christian; Benes, Bedrich; Skouras, Melina; Wang, He
    While the past of terrain cannot be known precisely because an effect can result from many different causes, exploring these possible pasts opens the way to numerous applications ranging from movies and games to paleogeography. We introduce unerosion, an attempt to recover plausible past topographies from an input terrain represented as a height field. Our solution relies on novel algorithms for the backward simulation of different processes: fluvial erosion, sedimentation, and thermal erosion. This is achieved by re-formulating the equations of erosion and sedimentation so that they can be simulated back in time. These algorithms can be combined to account for a succession of climate changes backward in time, while the possible ambiguities provide editing options to the user. Results show that our solution can approximately reverse different types of erosion while enabling users to explore a variety of alternative pasts. Using a chronology of climatic periods to inform us about the main erosion phenomena, we also went back in time using real measured terrain data. We checked the consistency with geological findings, namely the height of river beds hundreds of thousands of years ago.
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    PropColor: Interactive Color Propagation for 2D Animations
    (The Eurographics Association, 2024) Gowtham, Hari Hara; Parakkat, Amal Dev; Cani, Marie-Paule; Linsen, Lars; Thies, Justus
    Coloring is a fundamental yet time-consuming task in the 2D animation production pipeline. Traditional methods typically rely on frame-by-frame user interaction, leading to high user time and production costs. In this paper, we introduce PropColor, an interactive yet simple tool to propagate colors between adjacent frames of a hand-drawn animation. Starting with an initial frame colored by the user, our method propagates colors to neighboring frames based on the Delaunay triangulations computed from the sketch contours and the color hints. In addition to propagating colouring between frames, our method also associates a confidence score with each of them. This enables to identify the frames where user intervention is needed the most, either to validate the result or to provide additional color hints. Experiments show that our lightweight tool gives real-time feedback and significantly cuts down the animator's time.
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    Driller: An Intuitive Interface for Designing Tangled and Nested Shapes
    (The Eurographics Association, 2024) Butler, Tara; Guehl, Pascal; Parakkat, Amal Dev; Cani, Marie-Paule; Hu, Ruizhen; Charalambous, Panayiotis
    The ability to represent not only isolated shapes but also shapes that interact is essential in various fields, from design to biology or anatomy. In this paper, we propose an intuitive interface to control and edit complex shape arrangements. Using a set of pre-defined shapes that may intersect, our ''Driller'' interface allows users to trigger their local deformation so that they rest on each other, become tangled, or even nest within each other. Driller provides an intuitive way to specify the relative depth of different shapes beneath user-selected points of interest by setting their local depth ordering perpendicularly to the camera's viewpoint. Deformations are then automatically generated by locally propagating these ordering constraints. In addition to being part of the final arrangement, some of the shapes can be used as deformers, which can be later deleted to help sculpt the target shapes. We implemented this solution within a sketch-based modeling system designed for novice users.
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    Volcanic Skies: Coupling Explosive Eruptions with Atmospheric Simulation to Create Consistent Skyscapes
    (The Eurographics Association and John Wiley & Sons Ltd., 2024) Pretorius, Pieter C.; Gain, James; Lastic, Maud; Cordonnier, Guillaume; Chen, Jiong; Rohmer, Damien; Cani, Marie-Paule; Bermano, Amit H.; Kalogerakis, Evangelos
    Explosive volcanic eruptions rank among the most terrifying natural phenomena, and are thus frequently depicted in films, games, and other media, usually with a bespoke once-off solution. In this paper, we introduce the first general-purpose model for bi-directional interaction between the atmosphere and a volcano plume. In line with recent interactive volcano models, we approximate the plume dynamics with Lagrangian disks and spheres and the atmosphere with sparse layers of 2D Eulerian grids, enabling us to focus on the transfer of physical quantities such as temperature, ash, moisture, and wind velocity between these sub-models. We subsequently generate volumetric animations by noise-based procedural upsampling keyed to aspects of advection, convection, moisture, and ash content to generate a fully-realized volcanic skyscape. Our model captures most of the visually salient features emerging from volcano-sky interaction, such as windswept plumes, enmeshed cap, bell and skirt clouds, shockwave effects, ash rain, and sheathes of lightning visible in the dark.
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    Generating Flight Summaries Conforming to Cinematographic Principles
    (The Eurographics Association and John Wiley & Sons Ltd., 2024) Lino, Christophe; Cani, Marie-Paule; Skouras, Melina; Wang, He
    We propose an automatic method for generating flight summaries of prescribed duration, given any planed 3D trajectory of a flying object. The challenge is to select relevant time-ellipses, while keeping and adequately framing the most interesting parts of the trajectory, and enforcing cinematographic rules between the selected shots. Our solution optimizes the visual quality of the output video both in terms of camera view and film editing choices, thanks to a new optimization technique, designed to jointly optimize the selection of the interesting parts of a flight, and the camera animation parameters over time. To our best knowledge, this solution is the first one to address camera control, film editing, and trajectory summarizing at once. Ablation studies demonstrate the visual quality of the flights summaries we generate compared to alternative methods.
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    VRSurf: Surface Creation from Sparse, Unoriented 3D Strokes
    (The Eurographics Association and John Wiley & Sons Ltd., 2025) Sureshkumar, Anandhu; Parakkat, Amal Dev; Bonneau, Georges-Pierre; Hahmann, Stefanie; Cani, Marie-Paule; Bousseau, Adrien; Day, Angela
    Although intuitive, sketching a closed 3D shape directly in an immersive environment results in an unordered set of arbitrary strokes, which can be difficult to assemble into a closed surface. We tackle this challenge by introducing VRSurf, a surfacing method inspired by a balloon inflation metaphor: Seeded in the sparse scaffold formed by the strokes, a smooth, closed surface is inflated to progressively interpolate the input strokes, sampled into lists of points. These are treated in a divide-and-conquer manner, which allows for automatically triggering some additional balloon inflation followed by fusion if the current inflation stops due to a detected concavity. While the input strokes are intended to belong to the same smooth 3D shape, our method is robust to coarse VR input and does not require strokes to be aligned. We simply avoid intersecting strokes that might give an inconsistent surface position due to the roughness of the VR drawing. Moreover, no additional topological information is required, and all the user needs to do is specify the initial seeding location for the first balloon. The results show that VRsurf can efficiently generate smooth surfaces that interpolate sparse sets of unoriented strokes. Validation includes a side-by-side comparison with other reconstruction methods on the same input VR sketch. We also check that our solution matches the user's intent by applying it to strokes that were sketched on an existing 3D shape and comparing what we get to the original one.
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    ReConForM: Real-time Contact-aware Motion Retargeting for more Diverse Character Morphologies
    (The Eurographics Association and John Wiley & Sons Ltd., 2025) Cheynel, Théo; Rossi, Thomas; Bellot-Gurlet, Baptiste; Rohmer, Damien; Cani, Marie-Paule; Bousseau, Adrien; Day, Angela
    Preserving semantics, in particular in terms of contacts, is a key challenge when retargeting motion between characters of different morphologies. Our solution relies on a low-dimensional embedding of the character's mesh, based on rigged key vertices that are automatically transferred from the source to the target. Motion descriptors are extracted from the trajectories of these key vertices, providing an embedding that contains combined semantic information about both shape and pose. A novel, adaptive algorithm is then used to automatically select and weight the most relevant features over time, enabling us to efficiently optimize the target motion until it conforms to these constraints, so as to preserve the semantics of the source motion. Our solution allows extensions to several novel use-cases where morphology and mesh contacts were previously overlooked, such as multi-character retargeting and motion transfer on uneven terrains. As our results show, our method is able to achieve real-time retargeting onto a wide variety of characters. Extensive experiments and comparison with state-of-the-art methods using several relevant metrics demonstrate improved results, both in terms of motion smoothness and contact accuracy.
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    PerceptualLift: Using hatches to infer a 3D organic shape from a sketch
    (The Eurographics Association, 2025) Butler, Tara; Guehl, Pascal; Parakkat, Amal Dev; Cani, Marie-Paule; Catalano, Chiara Eva; Parakkat, Amal Dev
    In this work, we investigate whether artistic hatching, popular in pen-and-ink sketches, can be consistently perceived as a depth cue. We illustrate our results by presenting PerceptualLift, a modeling system that exploits hatching to create curved 3D shapes from a single sketch. We first describe a perceptual user study conducted across a diverse group of participants, which confirms the relevance of hatches as consistent clues for inferring curvature in the depth direction from a sketch. It enables us to extract geometrical rules that link 2D hatch characteristics, such as their direction, frequency, and magnitude, to the changes of depth in the depicted 3D shape. Built on these rules, we introduce PerceptualLift, a flexible tool to model 3D organic shapes by simply hatching over 2D hand-drawn contour sketches.
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    Expressive Rendering for 2D Animations of Liquids
    (The Eurographics Association, 2025) Regla, Rodrigo Stevenson; Rohmer, Damien; Barthe, Loïc; Cani, Marie-Paule; Berio, Daniel; Bruckert, Alexandre
    We describe a new rendering technique for expressive liquid surface 2D animation that can be used on top of existing particlebased simulations. We introduce a hybrid particle model that carries both water and air density distribution and can evolve through particle history. These material quantities combined with the kinematics information are then used to generate a scalar field, which can be parameterized to create an implicit iso-surface capturing stylized geometry commonly seen in paintings and cartoons. We propose, in particular, to represent behavior highlighting the dynamical aspect of the scene, such as elongated droplet behavior and curl-like shapes found in breaking waves.