Controlling Deformable Material with Dynamic Morph Targets
Nico Galoppo, Miguel A. Otaduy, William Moss, Jason Sewall, Sean Curtis, Ming C. Lin
We present a method to control the behavior of elastic, deformable
material in a dynamic simulation. We introduce dynamic morph
targets, the equivalent in dynamic simulation to the geometric
morph targets in (quasi-static) modeling. Dynamic morph targets
define the pose-dependent physical state of soft objects, including
surface deformation and elastic and inertial properties. Given these
morph targets, our algorithm then derives a dynamic model that can
be simulated in time-pose-space, interpolating the dynamic morph
targets at the input poses. Our method easily integrates with current
modeling and animation pipelines: at different poses, an artist simply
provides a set of dynamic morph targets. Whether these input
states are physically plausible is completely up to the artist. The
resulting deformable models expose fully dynamic, pose-dependent
behavior, driven by the artist-provided morph targets, complete
with inertial effects.
Our deformable models are computationally efficient at runtime
through modal reduction and pose-space polynomial interpolation.
These models can therefore be plugged into existing dynamic
simulation engines, either forming interactive, deformable
content in real-time games or providing secondary dynamic effects
for kinematically-driven characters in feature animation films. Finally,
our method also facilitates certain time-consuming rigging
procedures, by providing a physically based approach to resolve
co-articulation deficiencies in traditional skinning methods, such as
in shoulder regions, fully automatically.
ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games ||
paper (pdf)
Visual Simulation of Shockwaves
Jason Sewall, Nico Galoppo, Georgi Tsankov, Ming C. Lin
We present an efficient method for visual simulations of shock phenomena
in compressible, inviscid fluids. Our algorithm is derived from one
class of the finite volume method especially designed for capturing
shock propagation, but offers improved efficiency through
physically-based simplification and adaptation for graphical rendering.
Our technique is well suited for parallel implementation on multicore
architectures and is also capable of handling complex, bidirectional
object-shock interactions stably and robustly. We describe its
applications to various visual effects, including explosion, sonic booms
and turbulent flows.
ACM SIGGRAPH/Eurographics Symp. on
Computer Animation, Dublin, 2008 || website
Accelerated wave-based acoustics simulation
Nikunj Raghuvanshi, Nico Galoppo, Ming C. Lin
We present an efficient technique to model sound propagation accurately
in an arbitrary 3D scene by numerically integrating the wave equation.
We show that we can simulate sound propagation accurately using a coarse
mesh to enable highly accelerated computation and to reduce the memory
requirements as well. We present a domain decomposition approach to
drastically shorten the pre-processing time, while minimizing the
resulting performance degradation at runtime. We introduce a simple,
efficient and stable technique for handling the communication between
the domain partitions. We validate the accuracy of our approach against
cases with known analytical solutions. With our approach, we have
observed upto two orders of magnitude speedup compared to a naive
implementation.
ACM Symposium on Solid and Physical Modeling 2008 || website
Soft Articulated Characters with Fast Contact Handling
Nico Galoppo, Miguel A. Otaduy, Serhat Tekin,
Markus Gross, Ming C. Lin
Fast contact handling of soft articulated characters is a
computationally challenging problem, in part due to complex interplay
between skeletal and surface deformation. We present a fast, novel
algorithm based on a layered representation for articulated bodies
that enables physically-plausible simulation of animated characters
with a high-resolution deformable skin in real time.
Our algorithm gracefully captures the dynamic skeleton-skin interplay
through a novel formulation of elastic deformation in the pose space
of the skinned surface. The algorithm also overcomes the computational
challenges by robustly decoupling skeleton and skin computations using
careful approximations of Schur complements, and efficiently
performing collision queries by exploiting the layered representation.
With this approach, we can simultaneously handle large contact areas,
produce rich surface deformations, and capture the collision response
of a character's skeleton.
Computer Graphics Forum Vol.26(3) (Proc. of
Eurographics 2007) || website
Fast Simulation of Deformable Models in Contact Using
Dynamic Deformation Textures
Nico Galoppo, Miguel A. Otaduy, Paul Mecklenburg,
Markus Gross, Ming C. Lin
We present an efficient algorithm for simulating contacts between
deformable bodies with high-resolution surface geometry using dynamic
deformation textures, which reformulate the 3D elastoplastic
deformation and collision handling on a 2D parametric atlas to reduce
the extremely high number of degrees of freedom arising from large
contact regions and high-resolution geometry. Such computationally
challenging dynamic contact scenarios arise when objects with rich
surface geometry are rubbed against each other while they bounce, roll
or slide through the scene.
We simulate real-world deformable solids that can be modeled as a rigid
core covered by a layer of deformable material, assuming that the
deformation field of the surface can be expressed as a function in the
parametric domain of the rigid core. Examples include animated
characters, furniture, toys, tires, etc.
We have developed novel and efficient solutions for physically-based
simulation of dynamic deformations, as well as for collision detection
and robust contact response, by exploiting the layered representation
of the models and decoupling the degrees of freedom between the core
and the deformation layers.
A Simulation-based VR System for Interactive Hairstyling
Kelly Ward, Nico Galoppo, Ming C. Lin
User interaction with animated hair is desirable for various
applications but difficult because it requires real-time animation and
rendering of hair. Hair modeling, including styling, simulation, and
rendering, is computationally challenging due to the enormous number of
deformable hair strands on a human head, elevating the computational
complexity of many essential steps, such as collision detection and
self-shadowing for hair. Using multi-resolution simulation techniques
and graphics hardware rendering acceleration, we have developed a
physically-based virtual hair salon system that simulates and renders
hair at accelerated rates, enabling users to interactively style virtual
hair. With a 3D haptic interface, users can directly manipulate and
position hair strands, as well as employ real-world styling applications
(cutting, blow-drying, etc.) to create hairstyles more intuitively than
previous techniques.
Proc. of IEEE VR 2006, Applications and Research Sketches || website
LU-GPU: Algorithms for Dense Linear Systems on Graphics Hardware
Nico Galoppo, Naga Govindaraju, Michael Henson, Dinesh Manocha
We present a novel algorithm to solve dense linear systems using
graphics processors (GPUs). We reduce matrix decomposition and row
operations to a series of rasterization problems on the GPU architecure.
These include new techniques for streaming index pairs, swapping rows
and columns and parallelizing the computation to utilize multiple vertex
and fragment processors. We also choose appropriate data representations
to match the rasterization order and cache technology of graphics
hardware. The performance of our algorithm is on par with the fastest
CPU-based algorithms and implementations. Moreover, our results show
that our algorithm is cache and bandwidth efficient and scales well with
the number of fragment processors and the core GPU clock rate. We use
our algorithm for fluid flow simulation and demonstrate that the
commodity GPU is a useful co-processor for many scientific applications.
Proc. of ACM SuperComputing 2005, Seattle, WA || website
Adaptive Dynamics of Articulated Bodies
Stephane Redon, Nico Galoppo, Minc C. Lin
This paper introduces an algorithm for automatic simplification of
articulated body dynamics: an animator specifies the number of joints
that should be simulated in the articulated body, and the algorithm
automatically determines which joints should be simulated in order to
best approximate the articulated body motion. The other joints are
rigidified.
Depending on the amount of simplification specified by the animator, this algorithm potentially allows for a significant speed-up compared to traditional linear time forward dynamics algorithms.
In ACM Transactions on Graphics, 24(3).
Proc. of ACM SIGGRAPH 2005, Los Angeles, CA || website
Modeling Hair Influenced by Water and Styling Products
Kelly Ward, Nico Galoppo, Ming C. Lin
In the natural world, the physical behavior and appearance of hair is largely influenced by the external substances present on it, such as water or cosmetic styling products (e.g. hairspray). Yet, the influences of these substances are ignored in existing graphical hair modeling systems. We present novel methods for capturing the key characteristics of hair influenced by water and styling products. Our method includes a dynamics system that adaptively accounts for changing stiffness and weight of hair, a geometric representation that can alter the physical depiction of hair based on the substance(s) present on it, and a rendering approach to account for the varying appearance of hair. Additionally, our system captures the complex interactions between hairs in the presence of the external substances. Strands of hair can dynamically bond together due to the introduction of water or styling products. All of these properties can vary on the fly as water or styling products are applied to the hair.
Proc. of Computer Animation and Social Agents
2004 (CASA), Geneva, Switzerland ||
website
Technical reports and Projects
Pulsk: Impulse based Stacking for Rigid Bodies
The purpose of this project is to investigate novel methods for
simulation of rigid bodies that integrate well with stacking situations.
This work focuses on impulse-based simulation techniques with physical
interactions such as collision, contact and friction in relatively
complex scenes: large number of stacked objects, sliding objects,
highly dynamical scenes with non-convex bodies. We want the work to be
applicable to real-time applications such as games, therefore we allow
some small approximations in the algorithm. Nevertheless, this report
will show that we have succeeded in keeping the algorithm as physically
correct as possible.
COMP259 Physically Based Modeling (Ming C. Lin) final
project || pulsk project website
