35-Issue 2

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https://diglib.eg.org/handle/10.2312/15061

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Browsing 35-Issue 2 by Subject "Computer Graphics [I.3.7]"

Now showing 1 - 3 of 3
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    Animation Setup Transfer for 3D Characters
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Avril, Quentin; Ghafourzadeh, Donya; Ramachandran, Srinivasan; Fallahdoust, Sahel; Ribet, Sarah; Dionne, Olivier; Lasa, Martin de; Paquette, Eric; Joaquim Jorge and Ming Lin
    We present a general method for transferring skeletons and skinning weights between characters with distinct mesh topologies. Our pipeline takes as inputs a source character rig (consisting of a mesh, a transformation hierarchy of joints, and skinning weights) and a target character mesh. From these inputs, we compute joint locations and orientations that embed the source skeleton in the target mesh, as well as skinning weights to bind the target geometry to the new skeleton. Our method consists of two key steps. We first compute the geometric correspondence between source and target meshes using a semi-automatic method relying on a set of markers. The resulting geometric correspondence is then used to formulate attribute transfer as an energy minimization and filtering problem. We demonstrate our approach on a variety of source and target bipedal characters, varying in mesh topology and morphology. Several examples demonstrate that the target characters behave well when animated with either forward or inverse kinematics. Via these examples, we show that our method preserves subtle artistic variations; spatial relationships between geometry and joints, as well as skinning weight details, are accurately maintained. Our proposed pipeline opens up many exciting possibilities to quickly animate novel characters by reusing existing production assets.
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    Effect of Low-level Visual Details in Perception of Deformation
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Han, Donghui; Keyser, John; Joaquim Jorge and Ming Lin
    We quantitatively measure how different low-level visual details can influence people's perceived stiffness of a deformable sphere under physically based simulation. The result can be used to create a metric for artists in designing textures to enhance or reduce the stiffness perceived by a viewer. We use a checkerboard texture to render the simulation of a free falling sphere that collides with the ground and bounces up. We vary the spatial frequency and contrast of the checkerboard pattern according to results seen in a previous study on the Spatial- Temporal Contrast Sensitivity Function (CSF).We find that checkerboard pattern with certain combinations of spatial frequency and contrast can reduce the perceived stiffness. We also add a high contrast checkerboard background to study how complex backgrounds can influence the effect of low-level details in textures of foreground objects. Our study shows that the effect of low-level visual details in foreground objects observed previously disappears in this situation. This indicates the importance of background, even if it is static.
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    A Practical and Controllable Hair and Fur Model for Production Path Tracing
    (The Eurographics Association and John Wiley & Sons Ltd., 2016) Chiang, Matt Jen-Yuan; Bitterli, Benedikt; Tappan, Chuck; Burley, Brent; Joaquim Jorge and Ming Lin
    We present an energy-conserving fiber shading model for hair and fur that is efficient enough for path tracing. Our model adopts a near-field formulation to avoid the expensive integral across the fiber, accounts for all high order internal reflection events with a single lobe, and proposes a novel, closed-form distribution for azimuthal roughness based on the logistic distribution. Additionally, we derive, through simulation, a parameterization that relates intuitive user controls such as multiple-scattering albedo and isotropic cylinder roughness to the underlying physical parameters.