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Archive for the ‘PhysX Research’ Category

PhysX Research: Fast Simulation of Inextensible Hair and Fur

without comments

New “Fast Simulation of Inextensible Hair and Fur” paper from Dr. Matthias Müller-Fischer and PhysX Research team is a further extension of the work on realtime fur and hair simulation, previously demonstrated at GDC 2012.

Update: Introducing NVIDIA HairWorks – fur and hair simulation solution, based on the research

In this short paper we focus on the fast simulation of hair and fur on animated characters. While it is common in films to simulate single hair strands on virtual humans and on furry animals, those features are either not present on characters in computer games or modeled with simplified textured meshes. The main difficulty of simulating hair in real time applications is the sheer number of hair strands and the fact that each hair is inextensible. Keeping thousands of deformable objects from being stretched is computationally expensive.

In this paper, we present a robust method for simulating hair and fur that guarantees inextensiblity with a single iteration per frame. For an iteration count this low, existing methods either become unstable or introduce a substantial amount of stretching. Our method is geometric in nature and able to simulate thousands of inextensible hair strands in real time.

Like with any other research projects, there is a high probability that this particular technology will be utilized in future releases of PhysX SDK or APEX.

Written by Zogrim

December 21st, 2012 at 11:10 am

PhysX Research: Mass Splitting for Jitter-Free Parallel Rigid Body Simulation

with one comment

We want to draw your attention to the following SIGGRAPH 2012 paper, called “Mass Splitting for Jitter-Free Parallel Rigid Body Simulation” by Richard Tonge (NVIDIA), Feodor Benevolenski (NVIDIA) and Andrey Voroshilov (NVIDIA).

GPU Rigid Body solver, described in this paper, was already presented to public as part of APEX Destruction 1.1 module and UDK/UE3 integration.

We present a parallel iterative rigid body solver that avoids common artifacts at low iteration counts. In large or real-time simulations, iteration is often terminated before convergence to maximize scene size. If the distribution of the resulting residual energy varies too much from frame to frame, then bodies close to rest can visibly jitter. Projected Gauss-Seidel (PGS) distributes the residual according to the order in which contacts are processed, and preserving the order in parallel implementations is very challenging. In contrast, Jacobi-based methods provide order independence, but have slower convergence.

We accelerate projected Jacobi by dividing each body mass term in the effective mass by the number of contacts acting on the body, but use the full mass to apply impulses. We further accelerate the method by solving contacts in blocks, providing wallclock performance competitive with PGS while avoiding visible artifacts. We prove convergence to the solution of the underlying linear complementarity problem and present results for our GPU implementation, which can simulate a pile of 5000 objects with no visible jittering at over 60 FPS.

As you may see, one of the main features of this solver is fast and stable simulation without jittering, even with high number of contacts.

Thanks to Jesse Stiller for the link.

Written by Zogrim

July 29th, 2012 at 2:59 pm

Posted in Articles, Reviews, PhysX Research

Tagged with ,

PhysX Research: Mass-Conserving Liquids and cloth with Long Range Attachments

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More interesting papers from PhysX research team and Dr. Matthias Müller-Fischer, PhysX SDK Research Lead in NVIDIA.

First paper, called “Mass-Conserving Eulerian Liquid Simulation“, present latest advancements in hybrid fluid solver development – a topic of active research for past several years [previous work].

We present a GPU friendly, Eulerian, free surface fluid simulation method that conserves mass locally and globally without the use of Lagrangian components. Local mass conservation prevents small scale details of the free surface from disappearing, a problem that plagues many previous approaches, while global mass conservation ensures that the total volume of the liquid does not decrease over time. Our method handles moving solid boundaries as well as cells that are partially filled with solids. Due to its stability, it allows the use of large time steps which makes it suitable for both off-line and real-time applications.

We achieve this by using density based surface tracking with a novel, unconditionally stable, conservative advection scheme and a novel interface sharpening method. While our approach conserves mass, volume loss is still possible but only temporarily. With constant mass, local volume loss causes a local increase of the density used for surface tracking which we detect and correct over time. We also propose a density post-processing method to reveal sub-grid details of the liquid surface.We show the effectiveness of the proposed method in several practical examples all running either at interactive rates or in real-time.

At some point this research may be made into new APEX module, according to our information.

Read the rest of this entry »

Written by Zogrim

July 20th, 2012 at 6:20 pm

PhysX Research: Oriented Particles solver through CUDA

without comments

Earlier this year, Matthias Müller-Fischer, PhysX SDK Research Lead in NVIDIA, has presented new universal solver that can be used simulate almost any kind of objects – rigid, plastic, cloth or soft body.

You can familiarize with this work via previously published research papers: Solid Simulation with Oriented Particles and Adding Physics to Animated Characters with Oriented Particles.

Today, interesting video was revealed – it is showcasing impressive 20x performance improvement for this type of simulation running on GPU through CUDA, in comparison to CPU execution (5 “Lionfish” objects on CPU vs 100 on GPU – in real-time).

Sometimes findings of PhysX Research team are incorporated in PhysX/APEX products, and sometimes, for various reasons, they just become a research paper or presentation. We hope that in case with solver there will be only one option – first one.

Written by Zogrim

November 4th, 2011 at 6:23 pm

PhysX Research: adding physics to animated characters with Oriented Particles

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Another interesting research paper was published by Dr. Matthias Müller-Fischer, PhysX SDK Research Lead in NVIDIA.

Update: Oriented Particles solver through CUDA

It is called Adding Physics to Animated Characters with Oriented Particles and it further expands oriented particles approach with techniques for simulation of clothing on animated characters.

Abstract:

We present a method to enhance the realism of animated characters by adding physically based secondary motion to deformable parts such as cloth, skin or hair. To this end, we extend the oriented particles approach to incorporate animation information. In addition, we introduce techniques to increase the stability of the original method in order to make it suitable for the fast and sudden motions that typically occur in computer games. We also propose a method for the semi-automatic creation of particle representations from arbitrary visual meshes. This way, our technique allows us to simulate complex geometry such as hair, thick cloth with ornaments and multi-layered clothing, all interacting with each other and the animated character.

Written by Zogrim

September 14th, 2011 at 11:14 pm

PhysX Research: Eulerian Water Simulation and Solids through Oriented Particles

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Two new research papers have landed on a homepage of Dr. Matthias Müller-Fischer, PhysX SDK Research Lead in NVIDIA and NovodeX co-founder.

Fisrst one, called “Real-Time Eulerian Water Simulation Using a Restricted Tall Cell Grid“, presents further impovements to the real-time hybrid fluid solver, that we were able to see in recent demos like Lighhouse and Raging Rapids Ride.

Abstract:

We present a new Eulerian fluid simulation method, which allows real-time simulations of large scale three dimensional liquids. Such scenarios have hither to been restricted to the domain of off-line computation. To reduce computation time we use a hybrid grid representation composed of regular cubic cells on top of a layer of tall cells. With this layout water above an arbitrary terrain can be represented without consuming an excessive amount of memory and compute power, while focusing effort on the area near the surface where it most matters. Additionally, we optimized the grid representation for a GPU implementation of the fluid solver.

To further accelerate the simulation, we introduce a specialized multigrid algorithm for solving the Poisson equation and propose solver modifications to keep the simulation stable for large time steps. We demonstrate the efficiency of our approach in several real-world scenarios, all running above 30 frames per second on a modern GPU. Some scenes include additional features such as two-way rigid body coupling as well as particle representations of sub-grid detail.

We badly want to see this one in further releases of PhysX SDK 3 or APEX.

Read the rest of this entry »

Written by Zogrim

May 19th, 2011 at 10:54 am

PhysX Research: Anisotropic Turbulence Particles

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Interesting paper, called “Scalable Fluid Simulation using Anisotropic Turbulence Particles” has appeared at homepage of Dr. Markuss Gross, from ETH Zurich.

As far as we know, same solver is used in APEX Turbulence module.

APEX Turbulence paper

Abstract:

It is usually difficult to resolve the fine details of turbulent flows, especially when targeting real-time applications. We present a novel, scalable turbulence method that uses a realistic energy model and an efficient particle representation that allows for the accurate and robust simulation of small-scale detail. We compute transport of turbulent energy using a complete two-equation k–e model with accurate production terms that allows us to capture anisotropic turbulence effects, which integrate smoothly into the base flow. We only require a very low grid resolution to resolve the underlying base flow.

As we offload complexity from the fluid solver to the particle system, we can control the detail of the simulation easily by adjusting the number of particles, without changing the large scale behavior. In addition, no computations are wasted on areas that are not visible. We demonstrate that due to the design of our algorithm it is highly suitable for massively parallel architectures, and is able to generate detailed turbulent

In addition, this paper comes with nice video demonstration (92 mb). It is worth to watch.

Thanks to AquaGeneral for the link.

Written by Zogrim

September 30th, 2010 at 4:06 pm

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