SCA 16: Eurographics/SIGGRAPH Symposium on Computer Animation
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Browsing SCA 16: Eurographics/SIGGRAPH Symposium on Computer Animation by Subject "I.6.8 [Computer Graphics]"
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Item Compressing Fluid Subspaces(The Eurographics Association, 2016) Jones, Aaron Demby; Sen, Pradeep; Kim, Theodore; Ladislav Kavan and Chris WojtanSubspace fluid simulations, also known as reduced-order simulations, can be extremely fast, but also require basis matrices that consume an enormous amount of memory. Motivated by the extreme sparsity of Laplacian eigenfunctions in the frequency domain, we design a frequency-space codec that is capable of compressing basis matrices by up to an order of magnitude. However, if computed naïvely, decompression can be highly inefficient and dominate the running time, effectively negating the advantage of the subspace approach. We show how to significantly accelerate the decompressor by performing the key matrix-vector product in the sparse frequency domain. Subsequently, our codec only adds a factor of three or four to the overall runtime. The compression preserves the overall quality of the simulation, which we show in a variety of examples.Item Position and Orientation Based Cosserat Rods(The Eurographics Association, 2016) Kugelstadt, Tassilo; Schömer, Elmar; Ladislav Kavan and Chris WojtanWe present a novel method to simulate bending and torsion of elastic rods within the position-based dynamics (PBD) framework. The main challenge is that torsion effects of Cosserat rods are described in terms of material frames which are attached to the centerline of the rod. But frames or orientations do not fit into the classical position-based dynamics formulation. To solve this problem we introduce new types of constraints to couple orientations which are represented by unit quaternions. For constraint projection quaternions are treated in the exact same way as positions. Unit length is enforced with an additional constraint. This allows us to use the strain measures form Cosserat theory directly as constraints in PBD. It leads to very simple algebraic expressions for the correction displacements which only contain quaternion products and additions. Our results show that our method is very robust and accurately produces the complex bending and torsion effects of rods. Due to its simplicity our method is very efficient and more than one order of magnitude faster than existing position-based rod simulation methods. It even achieves the same performance as position-based simulations without torsion effects.