general overview. why physics ? because most things in our everyday environment can be described by...

General Overview

General Overview

Why physics ?

• Because most things in our everydayenvironment can be described by physics –and a common ambition in a simulation is to describe an environment

• Physical simulations capture complexity

• Complex behavior emerges from simulation

General Overview

Luxo Jr. by John Lasseter, Pixar 1987

• Keyframed realistic animation with nophysical simulation.

• Still, physics does the trick…

• High level motion control: Jump from A to B

• Luxo Jr. made people start thinking about physics . . .

General Overview

Physics is . . .

• Systematic

• Scalable

• Consequent

• Controllable

• Extensible

• General

Therefore library software and expertise can evolve !

General Overview

Applying Physics can create . . .

• Dynamics (Newton’s Laws)• Rigid Body Dynamics, Interaction, Collisions• Mechanics of Materials• Fluids, water (water, yacht)• Gases, smoke, clouds (smoke, train, interactive, clouds)• Plasmas, fire, lightning, sparks (candle)• Particles (special effects, explosions, fountain, hair, fur)• Fields• Body interaction• Collective phenomena, complex systems, emergence, …• Audio – wave tracing, acoustics, damping, …• Light – optics, ray tracing, …• Effectors and sensors – display and interaction

In the Beginning . . .


• Computers were hulking Goliaths locked in air-conditioned rooms.

• But a young electrical engineer and former naval radar technician named Douglas Engelbart viewed them differently.

• Engelbart envisioned them as tools for digital display.

• He knew from his days with radar that any digital information could be viewed on a screen. Why not, he then reasoned, connect the computer to a screen and use both to solve problems?


• Engelbart's ideas were dismissed, but by the early 1960s other people were thinking the same way.

• Moreover, the time was right for his vision of computing. Communications technology was intersecting with computing and graphics technology.

• This synergy yielded more user-friendly computers, which laid the groundwork for personal computers, computer graphics, and later simulations.


Pivotal Points in History . . .

Fear of nuclear attack prompted the U.S. military to commission a new radar system that would process large amounts of information and immediately display it in a form that humans could readily understand. The resulting radar defense system was the first "real time," or instantaneous, simulation of data.

• Aircraft designers began experimenting with ways for computers to graphically display, or model, air flow data.

• Computer experts began restructuring computers so they would display these models as well as compute them. The designers' work paved the way for scientific visualization, an advanced form of computer modeling that expresses multiple sets of data as images and simulations.


More Pivotal Points in History . . .

• One of the most influential antecedents of today’s simulations was the flight simulator. Following World War II and through the 1990s, the military and industrial complex pumped millions of dollars into technology to simulate flying airplanes (and later driving tanks and steering ships).

• By the 1970s, computer-generated graphics had replaced videos and models. These flight simulations were operating in real time, though the graphics were primitive. By the early 1980s, better software, hardware, and motion-control platforms enabled pilots to navigate through highly detailed virtual worlds.


Even More Pivotal Points History . . .

• Of course, the "military-industrial complex" was not the only entity interested in computer graphics.

•A natural consumer of computer graphics was the entertainment industry, which, like the military and industry, was the source of many valuable spin-offs in virtual reality.

• By the 1970s, some of Hollywood's most dazzling special effects were computer-generated, such as the battle scenes in the big-budget, blockbuster science fiction movie Star Wars, which was released in 1976. Later came such movies as Terminator and Jurassic Park. In the early 1980s, the video game business boomed.

Engineering Techniques and Feats in Physics Simulation

Current Climate

• Physics-based simulation is the art of reducing algorithmic complexity to achieve usable results with as little computation as possible.

• Current visualizations usually incorporate both scientific simulations based on research data and parametric rule-sets that augment the data and save time.

• State of the art simulation technology in this field is most often proprietary and created by specialized teams (scientists, engineers, artists, specialists) when the need for them arises.

• A large amount of cooperation between research institutions, productions houses, and software developers is needed and planning for computational demands is highly coordinated.

Current Climate

Some General Approaches Used:

• System Modeling (pre-computed) – Simulation based on equations (x,y,z,t) that are computed for individual data points (the more the better).

• Parametric Rule-Sets (pre-computed) – Integrates pre-computed systems with other simulations (from artists or augmented and reduced systems) based on defined parameters.

• Selective Data Plotting (real-time) – Compute only the data points you need to get an accurate representation of your system. Example: Ray-casting

• Monte Carlo Simulation (depends on application) – Compute complex systems using algorithms with reduced complexity by guessing (using known boundaries).

Current Climate

Areas Where Simulations Are Used in the Industry:

• Newtonian Physics - Rigid Body Kinetics, Object Collisions, etc.

• Realistic Human Movement – Muscle Behavior, Skeleton Behavior, etc.

• Volumetric Rendering – Natural Phenomenon (fire, smoke, clouds, fluids, solid bodies)

• Large-Scale Simulations – Flocking, Group Behavior, and Character Interaction

Newtonian Physics

• Newest implementation allows user control over bodies.

• Basic laws of Newtonian physics are readily defined (ex: a(t) = v’(t) = s’’(t)).

• Uses algorithms with interpolate the appropriate physical simulation based on user-defined actions (similar to key-framing).

• Current hurdles involve number of bodies, which can interact in real-time, and how many parameters are checked for each instance of time.

• Research at Carnegie Mellon University and implementation using controller packages like Maya, Houdini, and Softimage.

Realistic Human Movement

• A new technique is being developed at the University of Toronto that creates a composable controller system for human movement.

• It links motor abilities of characters to physics-based controllers.

• This is different from traditional character animation because character responds to interactions based on laws of physics.

• This is done through the groups of linked controllers that contain physical parameters.

Volumetric Rendering

• This technique has been too computationally intensive (usually N^3 complexity) in the past.

• In the last couple of years new technologies and techniques have arisen to reduce the complexity.

• Ray-casting – This method computes only the portions of the volume that are seen given the current projection.

• Volumetric models of systems areimportant because they are easily integrated with both pre-computed system model data and parametric rule-sets to create realistic behavior.

Volumetric Technologies

• Arete Digital Nature tools used in Cinema. Creates volumetric fluids, clouds, etc.

• Real-time volumetric renderings can still not be computed accurately on standard computer hardware without an additional accelerator.

• Mitsubishi Electronics RTViz group produced to VolumePro 500 and VolumePro 1000 to do ray-casting in real-time.

• Uses a large frame buffer and specialized hardware to compute 2563 individual volumes at 30 fps.

• Nvidia developed a technology (VTC) that compresses 3D textures (representing slices of a volumetric object).

Large Scale Simulation

Particles and Flocking:

• Uses a large number of discrete objects (with physical parameters and or simulation data attached) to model systems in which many bodies are interacting non-uniformly.

• Examples are crowds, swarms, and flocks, which could represent characters or environmental phenomenon.

• Large-scale simulations are usually coupled with other technologies such a volumetric rendering and Newtonian physics.

• Weta’s Massive is a very advanced, state of the art implementation of large-scale simulation.

Current Feats

LOTR Two Towers:

• Weta used its proprietary software Massive for large-scale simulation.

• It integrated Massive with its own physics-based muscle-system using Maya to create effects that would take 460 years to be rendered on a home PC.

• Rendering and simulation took 10 months and was done using about 1000 IBM and SGI workstations.

• Their own rendering and shading program Grunt was used with Massive to aid in simulating cloth and hair on individual characters in the crowd.

Recent Feats

A Perfect Storm:

• First film where ILM feels they created realistic fluid dynamics.

• Until recently, fluid flow simulations could only be run with 80-100 data points. In “A Perfect Storm” simulations of several different oceans were run in 3D using a much larger data set and various parameters until they looked right.

• Several simulation technologies went into recreating the ocean.

Simulating Physics in the Art World

Ability to manipulate/distort physics of their digital environment

Game Designer Perspective:

• Games allow Player to express himself

• Realism is not necessarily the goal for games

• Simulated World that has “Consistently”

Simulation for the Artist

Grenade example: grenade bounces realistically


Pro’s of digital simulation:

• Time Saved & Reduced costs

• Emergence – new strategies and game play by user

• Simulated World that has “Consistency”

• New and more genres of games created


Con’s of digital simulation:

• Unexpected methods of game play by player

• Being too complex or real for the game

• More user feedback is required

• Hardware limitations reduces use or ability

• Deeper simulation does not mean more fun. Maybe just more interesting


Thief by Looking Glass Studios:

Deeper awarenessmodel with complex sound propagation and lighting used for stimuli of characters



Sound simulatedto bounce off surfaces and materials withvaried intensity and reverb.



Designers added a “light gem” feedback deviceTo help the player utilize environments effectively


Simulation to the non-Game Artist:

3D programs like Maya 3D incorporate more simulationfor manipulating and controlling physics in 3D.


Simulation to the non-Game Artist:

KPT makes Adobe Photoshop plug-ins utilize 3D physics simulation of light &movement upon 2D surfaces.

Ex. Goo GelMaterizlier Turbulence

originalGoo plug-in


What the General Public will see:

• Simulation-based game design produce more variable player driven game play

• More dynamic effects in movies produced with digital tools

What Simulation means to the Public

Movie Industry Example:

LOTR Used motion-capturing to create cycles to be used with AI and physics to simulate mass warfare.

Future of Virtual Simulation and Visualization


• Current problems that keep our technology from advancing• Overcoming technological barriers and what

to expect from future simulation• Real-time simulation and visualization

• Advancements in representing human figures in motion

• Realistic walking movement• Physics-based human simulation for virtual prototyping

• Human populations in simulations• Technology that can be used for motion planning in robots


Problems that keep our Simulation technology from advancing

Today’s simulations require intense computational resources

• Most simulations generate gigabytes to terabytes of data, whether it is a scientific application or an artistic application such as movie effects• This Data requires not only huge amounts of storage space but also the computer processing power to handle it.


Example of a movie simulation: Water

When simulating water, dynamics and large scale 3D grids are used. Each point on the grid can generate thousands to millions of

particles that are tracked over time.


Example of a movie simulation: Water

The amount of data generated is so immense that in many cases artists must manually add in details because the movie production can

not afford so much simulation time.


Overcoming technological barriers and what to expect from future simulation

As computers get faster and storage space becomes cheaper, more complex and realistic

visualizations are possible

Real time visualization will revolutionize the world of simulation.


Real time means that the graphical outcome of a simulation will be available as the

computer works through the simulation.

What does this mean for artists?

Artists will be able to create very complex visuals without waiting to see the final

product. Changes will be possible without the fear of long rendering times.


What does this mean for scientists?

Scientists will be able to simultaneously get data from the simulation while analyzing the

computer visualization.


How far have we come with real time?

Pixar’s first film, “Luxo, Jr.” was made almost 17 years ago. The short film was rendered on a Cray supercomputer that took 75 hours per second of animation.

Future animatedfilms could be done entirelyon desktop machines as hardware advances.


Advancements in representing human figures in motion

Research is being done to develop systems to more realistically display human movement such as walking. Today’s systems pass for situations not intended to be “realistic” but when actual human-like figures are represented, we can notice that there is something not right.

Physics are what control human movement. The combination of physics and other techniques such as motion capturing can yield very realistic human motion. There is still a lot to hope for.


Characters moved almost too gracefully as real humans tend to be somewhat more jerky and unpredictable. We can expect to see much more realistic movement in future CG movies.

Final Fantasy uses CG to represent Humans

Square’s Final Fantasy: The Spirits Within raised the bar for technical achievement as it made digital actors look realistic.


Future Applications of Realistic Human Motion

Physics-based Human Simulationfor Virtual Prototyping

Boston Dynamics has been developinga landmark 3D software productfor real time simulations called DI-Guy. This software adds artificial human life to simulations such asvirtual battlefields.


Future Applications of Realistic Human Motion

Technology for Virtual Humans could provide potential for humanoid robots.

Robots use complex physics to performsimple motion. In the next 10 years,Humanoid robots could be a commonsight. The development of these newrobots could be furthered by the same research done to represent humanmovement graphically.

general overview. why physics ? because most things in our everyday environment can be described by...

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