Art and technolagy at pixar 2009 sig graph pdf

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art and technolagy at pixar 2009 sig graph pdf

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SIGGRAPH: ASIA 2009 (Program)

I research topics in physics-based simulation, including fire , water , and humans. My work has appeared in over two dozen movies, and I received a SciTech Oscar. Many of the results can be seen on YouTube , and extensive source code is available on this page. Plous Award Junior Faculty of the Year. I interned for Rhythm and Hues Studios in and Nicholas J. Weidner , T. Our approach, ConJac, is based on condensation, a technique for eliminating many degrees of freedom DOFs by expressing them in terms of the remaining degrees of freedom.

In this work, we choose a subset of nodes to be dynamic nodes, and apply condensation at the velocity level by defining a linear mapping from the velocities of these chosen dynamic DOFs to the velocities of the remaining quasistatic DOFs. We then use this mapping to derive reduced equations of motion involving only the dynamic DOFs.

We also derive a novel stabilization term that enables us to use complex nonlinear material models. ConJac remains stable at large time steps, exhibits highly dynamic motion, and displays minimal numerical damping. In marked contrast to subspace approaches, ConJac gives exactly the same configuration as the full space approach once the static state is reached. ConJac works with a wide range of moderate to stiff materials, supports anisotropy and heterogeneity, handles topology changes, and can be combined with existing solvers including rigid body dynamics.

A finite element formulation of baraff-witkin cloth. Kim Symposium on Computer Animation However, its relationship to the finite element method FEM has always been unclear, because the model resists being written as an isotropic, hyperelastic strain energy.

In this paper, we show that this is because the Baraff-Witkin model is actually a coupled anisotropic strain energy. We show that its stretching term approximates the isotropic As-Rigid-As-Possible ARAP energy, and its shearing term is a cross-fiber coupling energy common in biomechanics. While it has been known empirically for some time that the model can produce indefinite force Jacobians, the conditions under which they occur has never been clear.

Our formulation enables a complete eigenanalysis that precisely characterizes exactly when indefiniteness occurs, and leads to fast, analytic, semi-positive-definite projection methods. Finally, our analysis suggests a generalized Baraff-Witkin energy with non-orthogonal warp and weft directions.

The racist legacy of computer-generated humans. Kim Scientific American Recently, several key transformations have been applied to Pixar's core simulator Fizt that improve its speed, robustness, and generality. Starting with Coco , improved collision detection and response were incorporated into the cloth solver, then with Cars 3 3D solids were introduced, and in Onward clothing is allowed to interact with a character's body with two-way coupling.

Under this formulation, the construction and eigendecomposition of the force gradient, long considered the most onerous part of the implementation, becomes fast and simple. We provide a detailed, self-contained, and unified treatment here that is not available in the technical papers. This new formulation is only a starting point for creating a simulator that is up challenges of a production environment.

One challenge is performance: we discuss our current best practices for accelerating system assembly and solver performance. Another challenge that requires considerable attention is robust collision detection and response. Much has been written about collision detection approaches such as proximity-queries, continuous collisions and global intersection analysis.

We discuss our strategies for using these techniques, which provides us with valuable information that is needed to handle challenging scenarios. We present a new, numerically stable algorithm that allows us to compute a previously-infeasible, fractalized Stanford Bunny composed of 10 billion triangles. Recent work [Kim ] showed that it is feasible to compute quaternion Julia sets that conform to any arbitrary shape. However, the scalability of the technique was limited because it used high-order rationals requiring 80 bits of precision.

We address the sources of numerical difficulty and allow the same computation to be performed using 64 bits. Crucially, this enables computation on the GPU, and computing a 10 billion triangle model now takes 17 days instead of 10 years. We show that the resulting mesh is useful a test case for a distributed renderer.

Fast and robust stochastic structural optimization. Kim Computer Graphics Forum Eurographics While this approach is powerful, it is also quite slow, which has previously limited its use to coarse resolutions e. We show that this approach can be made asymptotically faster, which in practice reduces computation time by two orders of magnitude, and allows the use of previously-infeasible resolutions. We achieve this by showing that the probability gradient can be computed in linear time instead of quadratic, and by using a robust new scheme that stabilizes the inertia gradients used by the optimization.

Additionally, we propose a constrained restart method that deals with local minima, and a sheathing approach that further reduces the weight of the shape. Together, these components enable the discovery of previously-inaccessible designs. Anisotropic elasticity for inversion-safety and element rehabilitation.

We then use these to build fast and concise Newton implementations. We leverage our analysis in two separate applications. First, we show that existing anisotropic energies are not inversion-safe, and contain spurious stable states under large deformation. We then propose a new anisotropic strain invariant that enables the formulation of a novel, robust, and inversion-safe energy.

The new energy fits completely within our analysis, so closed-form expressions are obtained for its eigensystem as well. Secondly, we use our analysis to rehabilitate badly-conditioned finite elements. Using this method, we can robustly simulate large deformations even when a mesh contains degenerate, zero-volume elements. We accomplish this by swapping the badly-behaved isotropic direction with a well-behaved anisotropic term. We validate our approach on a variety of examples.

Deep fluids: a generative network for parameterized fluid simulations. A convolutional neural network is trained on a collection of discrete, parameterizable fluid simulation velocity fields. Due to the capability of deep learning architectures to learn representative features of the data, our generative model is able to accurately approximate the training data set, while providing plausible interpolated in-betweens. The proposed generative model is optimized for fluids by a novel loss function that guarantees divergence-free velocity fields at all times.

In addition, we demonstrate that we can handle complex parameterizations in reduced spaces, and advance simulations in time by integrating in the latent space with a second network.

Our method models a wide variety of fluid behaviors, thus enabling applications such as fast construction of simulations, interpolation of fluids with different parameters, time re-sampling, latent space simulations, and compression of fluid simulation data. Reconstructed velocity fields are generated up to x faster than re-simulating the data with the underlying CPU solver, while achieving compression rates of up to x.

Analytic eigensystems for isotropic distortion energies. Breannan Smith , Fernando de Goes, and T. In order to guarantee the positive semi-definiteness required by these methods, a numerical eigendecomposition or approximate regularization is usually needed. In this paper, we present analytic expressions for the eigensystems at each quadrature point of a wide range of isotropic distortion energies. These systems can then be used to project energy Hessians to positive semi-definiteness analytically.

Unlike previous attempts, our formulation provides compact expressions that are valid both in 2D and 3D, and does not introduce spurious degeneracies. At its core, our approach utilizes the invariants of the stretch tensor that arises from the polar decomposition of the deformation gradient. We provide closed-form expressions for the eigensystems for all these invariants, and use them to systematically derive the eigensystems of any isotropic energy. Our results are suitable for geometry optimization over flat surfaces or volumes, and agnostic to both the choice of discretization and basis function.

To demonstrate the efficiency of our approach, we include comparisons against existing methods on common graphics tasks such as surface parameterization and volume deformation.

Scalable laplacian eigenfluids. Qiaodong Cui , Pradeep Sen, and T. However, the approach does not scale well, as the memory cost grows prohibitively with the number of eigenfunctions. The method also lacks generality, because the dynamics are constrained to a closed box with Dirichlet boundaries, while open, Neumann boundaries are also needed in most practical scenarios. To address these limitations, we present a set of analytic eigenfunctions that supports uniform Neumann and Dirichlet conditions along each domain boundary, and show that by carefully applying the discrete sine and cosine transforms, the storage costs of the eigenfunctions can be made completely negligible.

The resulting algorithm is both faster and more memory-efficient than previous approaches, and able to achieve lower viscosities than similar pseudo-spectral methods. We are able to surpass the scalability of the original Laplacian Eigenfunction approach by over two orders of magnitude when simulating rectangular domains. Finally, we show that the formulation allows forward scattering to be directed in a way that is not possible with any other method.

Example-based turbulence style transfer. Syuhei Sato , Yoshinori Dobashi, T. To reduce such costs, several methods have been developed in which high-resolution turbulence is synthesized as a post process. Since global motion can then be obtained using a fast, low-resolution simulation, less effort is needed to create a realistic animation with the desired behavior. While much research has focused on accelerating the low-resolution simulation, the problem controlling the behavior of the turbulent, high-resolution motion has received little attention.

In this paper, we show that style transfer methods from image editing can be adapted to transfer the turbulent style of an existing fluid simulation onto a new one.

We do this by extending example-based image synthesis methods to handle velocity fields using a combination of patch-based and optimization-based texture synthesis. Importantly, this approach allows us to incorporate the incompressibility condition. Using our method, a user can easily and intuitively create high-resolution fluid animations that have a desired turbulent motion. Clean cloth inputs: removing character self-intersections with volume simulation.

Audrey Wong, David Eberle, and T. When these characters are sent as inputs to a cloth simulator, the results can often contain terrible artifacts that must be addressed by tediously sculpting either the input characters or the output cloth. In this talk, we apply volume simulation to character meshes and remove self-intersections before they are sent to the cloth simulator.

The technique has successfully dealt with very challenging animation scenarios in a production setting, and was applied to all the characters in the short film Bao. Robust skin simulation in Incredibles 2. Ryan Kautzman, Gordon Cameron, and T. Skin can become non-physically "snagged" in curved or creased regions, such as armpits, and create unusable results.

These problems usually arise when it becomes ambiguous which kinematic surface the skin should be sliding along.

Publications

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Physically based shading is increasingly important in both film and game production. By adhering to physically based, energy-conserving shading models, one can easily create high-quality, realistic materials that maintain their quality in a variety of lighting environments. Stephen Hill is a 3D Technical Lead at Ubisoft Montreal, where his current focus is on physically based methodologies. He previously held this role on Splinter Cell Conviction , where he helped steer development of the renderer over the entire five year development period. During that time, he developed novel systems for dynamic ambient occlusion and visibility. Stephen McAuley is a senior 3D programmer at Ubisoft Montreal, recently shipping Far Cry 3 , where he spearheaded the switch to physically based lighting and materials. Previously he spent five years at Bizarre Creations, where he worked on games such as Blood Stone , Blur and Project Gotham Racing , focusing on rendering architecture, physically based shading and deferred lighting.

Pol Jeremias Vila is a computer graphics engineer. Pol is currently a Lead Graphics Engineer at Pixar Animation Studios where he develops algorithms to help artists make movies. In , Beautypi released Shadertoy. Today, Shadertoy is one of the biggest repositories of computer graphics experiments, ideas, and projects. In , Beautypi released Memix , a software to improve video conferencing using computer graphics technology. Memix was acquired that same year by Mmhmm Inc.

Publications

Toggle nav. Computer-animated objects are ubiquitous in entertainment and training applications of computer graphics e. As opposed to tedious and rather inflexible key-frame animation, physics-based simulation offers a concise, but rich and flexible way of defining the behavior of animated objects, by allowing the laws of physics to determine or guide their motion.

Although this description may sound scary to most of us, this filter is nothing other than a basic weighted average. This simple tool has become ubiquitous in image processing and has shown remarkable abilities to filter images, videos, and even 3D meshes. Our course presents its most successful applications, describes its various implementations, and exposes in a comprehensive manner the related theoretical background. The attendees will learn progressively many basic concepts underpinning bilateral filtering.

I research topics in physics-based simulation, including fire , water , and humans. My work has appeared in over two dozen movies, and I received a SciTech Oscar. Many of the results can be seen on YouTube , and extensive source code is available on this page. Plous Award Junior Faculty of the Year.

SIGGRAPH 2013 Course: Physically Based Shading in Theory and Practice

With the fast increase of computational power and of memory space, increasingly complex and detailed 3D content is expected for virtual environments. Unfortunately, 3D modeling methodologies did not evolve as fast: most users still use standard CAD or 3D modeling software such as Maya, 3DS or Blender to design each 3D shape, to animate them and to manually control cameras for movie production.

Papers & Talks

Он перевел взгляд на соседнюю дверь, с табличкой DAMAS, подошел и громко постучал. - Hola? - крикнул он, приоткрыв дверь.  - Con permiso. Не дождавшись ответа, он вошел. Типичная для Испании туалетная комната: квадратная форма, белый кафель, с потолка свисает единственная лампочка. Как всегда, одна кабинка и один писсуар.

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