Browsing by Subject "physics-based animation"
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Item Deformation Embedding for Point-Based Elastoplastic Simulation(ACM, 2014-03) Jones, Ben; Ward, Stephen; Jallepalli, Ashok; Perenia, Joseph; Bargteil, Adam W.We present a straightforward, easy-to-implement, point-based approach for animating elastoplastic materials. The core idea of our approach is the introduction of embedded space—the least-squares best fit of the material’s rest state into three dimensions. Nearest neighbor queries in the embedded space efficiently update particle neighborhoods to account for plastic flow. These queries are simpler and more efficient than remeshing strategies employed in mesh-based finite element methods. We also introduce a new estimate for the volume of a particle, allowing particle masses to vary spatially and temporally with fixed density. Our approach can handle simultaneous extreme elastic and plastic deformations. We demonstrate our approach on a variety of examples that exhibit a wide range of material behaviors.Item Dynamic Sprites(ACM, 2013-11-06) Jones, Ben; Popovic, Jovan; McCann, James; Li, Wilmot; Bargteil, AdamTraditional methods for creating dynamic objects and characters from static drawings involve careful tweaking of animation curves and/or simulation parameters. Sprite sheets offer a more drawing-centric solution, but they do not encode timing information or the logic that determines how objects should transition between poses and cannot generalize outside the given drawings. We present an approach for creating dynamic sprites that leverages sprite sheets while addressing these limitations. In our system, artists create a drawing, deform it to specify a small number of example poses, and indicate which poses can be interpolated. To make the object move, we design a procedural simulation to navigate the pose manifold in response to external or user-controlled forces. Powerful artistic control is achieved by allowing the artist to specify both the pose manifold and how it is navigated, while physics is leveraged to provide timing and generality. We used our method to create sprites with a range of different dynamic properties.Item Dynamic Sprites: Artistic Authoring of Interactive Animations(ACM, 2015-03) Jones, Ben; Popovic, Jovan; McCann, James; Li, Wilmot; Bargteil, AdamTraditional methods for creating dynamic objects and characters from static drawings involve careful tweaking of animation curves and/or simulation parameters. Sprite sheets offer a more drawing-centric solution, but they do not encode timing information or the logic that determines how objects should transition between poses and cannot generalize outside the given drawings. We present an approach for creating dynamic sprites that leverages sprite sheets while addressing these limitations. In our system, artists create a drawing, deform it to specify a small number of example poses, and indicate which poses can be interpolated. To make the object move, we design a procedural simulation to navigate the pose manifold in response to external or user-controlled forces. Powerful artistic control is achieved by allowing the artist to specify both the pose manifold and how it is navigated, while physics is leveraged to provide timing and generality. We used our method to create sprites with a range of different dynamic propertiesItem Fluid Simulation on Unstructured Quadrilateral Surface MeshesBhattacharya, Haimasree; Levine, Joshua A.; Bargteil, Adam W.In this paper, we present a method for fluid simulation on unstructured quadrilateral surface meshes. We solve the Navier-Stokes equations by performing the traditional steps of fluid simulation, semi-Lagrangian advection and pressure projection, directly on the surface. We include level-set based front-tracking for visualizing “liquids,” while we use densities to visualize “smoke.” We demonstrate our method on a variety of meshes and create an assortment of visual effectsItem A Point-based Method for Animating Elastoplastic Solids(ACM, 2009-08-01) Gerszewski, Dan; Bhattacharya, Haimasree; Bargteil, Adam W.In this paper we describe a point-based approach for animating elastoplastic materials. Our primary contribution is a simple method for computing the deformation gradient for each particle in the simulation. The deformation gradient is computed for each particle by finding the affine transformation that best approximates the motion of neighboring particles over a single timestep. These transformations are then composed to compute the total deformation gradient that describes the deformation around a particle over the course of the simulation. Given the deformation gradient we can apply arbitrary constitutive models and compute the resulting elastic forces. Our method has two primary advantages: we do not store or compare to an initial rest configuration and we work directly with the deformation gradient. The first advantage avoids poor numerical conditioning and the second naturally leads to a multiplicative model of deformation appropriate for finite deformations. We demonstrate our approach on a number of examples that exhibit a wide range of material behaviors.