Visual Simulation of Waves

1. Visual Simulation of Waves Sarah Macumber 10/12/04

2. 4/12/2012 2 Overview Why is a storm so hard to model and visually simulate? The Perfect Storm Numerical simulations and models Movie magic

3. It’s just Water? Physical properties of water Density, viscosity and surface tension Color gradients Translucence Boundary layer between water and air

4. Its just a storm All of the water effects discussed above Non-linear wave interactions Wind Rain Rigid body interactions Foam from waves churning Mist Splashes Buoyancy characteristics Lightening

5. We cannot rely on Graphical Art Animation To provide us with a realistic Storm We NEED more MATH, a lot more … Mathematicians with cool jobs

6. 4/12/2012 6 The Perfect Storm In October of 1991 it hit off the coast of Massachusetts, lasting 5 days Stronger than any in recorded history Such an apocalyptic situation that meteorologists wanted to create a new category of storms for it No Name Storm, Halloween Storm, The Perfect Storm 2 Tropical and 1 Mid Atlantic storm combined Gale to Hurricane Force Winds 78-100 mph Boats encountered waves of 100 feet (10 story building) On shore waves reported 10 to 30 ft

7. 4/12/2012 7 Stormy Weather Model Accurate model of water particle Ocean base Statistical models of ocean behavior Inferred from oceanographic data Deep Waves 3D Navier Stokes model Surface Waves Particle system model Rigid body collision Lighting

8. 4/12/2012 8 Water Model Color Gradients and Translucence Density, Viscosity, Surface tension…etc Boundary layer between water and air Dense grid and high computational costs needed to capture interesting behavior

9. 4/12/2012 9 Statistical Model Provides for a basic model of the waves and wind Geography and topology Speed Height Direction Frequency Linear Assumes waves vary in a regular way around the average wave height

10. 4/12/2012 10 That Looks Bad

11. 4/12/2012 11 Navier Stokes model Finite Differences Finite Elements Finite Volumes Don’t have to worry about the boundary between the water and air Surface wave model *Note, this is the easiest step!

12. 4/12/2012 12 2D Navier Stokes on a Breaking Wave

13. 4/12/2012 13 Full 3D Navier Stokes on a Breaking Wave

14. 4/12/2012 14 Particle Systems Crests on the waves Mist Foam Millions of water droplets in each and every splash

15. 4/12/2012 15 Particle Systems Particles in wave interact with Other particles in the wave Other waves Rigid objects Wind Gravity

16. 4/12/2012 16 Particle Systems Particle Trajectories before collision Defined Chaotic Source diffusion (Heat eq) Collision Model tells each particle, as well as every other object in the scene, what to do when it comes into contact with the surface of another object, or with another particle Calculate and display the trajectories of each individual particle Require days of computation time per shot Use rooms full of parallel processing machines

17. 4/12/2012 17 Particle Systems Collision Model tells each particle, as well as every other object in the scene, what to do when it comes into contact with the surface of another object, or with another particle Millions and Billions of particles Calculate and display the trajectories of each individual particle Simulations for scenes require days of computation time per shot, using rooms full of high-speed computers!

18. 4/12/2012 18 I’m not Keeping track!

19. 4/12/2012 19 Lighting model Reflection Refraction Textured surface Godrays

20. 4/12/2012 20 Lighting Methods Flat shading Position and intensity of a light source Texture mapping Mapping images (textures) onto polygons Bump mapping Normal perturbation method, simulates wrinkled surfaces Raytracing Simulates reflection and transparency Global Illumination Monte-Carlo gathering and radiosity for simulating realistic light sources.

21. 4/12/2012 21 Lighting Direct Lighting Monte Carlo Ray tracing Markov chain random walk technique for solving rendering equation

22. 4/12/2012 22 Movie Magic

23. 4/12/2012 23 Industrial Light & Magic Works Responsible for the CG affects in Warner Bros. movie The Perfect Storm Visualize and plan the scene Create an ocean environment storm, Andrea Gale and actors Integrate the CG storm into real water from live shots Touch ups & post production Convince the audience that its real

24. 4/12/2012 24 Animatics Allow the director to plan the shot both visually and practically are not adequate representations for a fluid because of its amorphous nature and irregular topology.are not adequate representations for a fluid because of its amorphous nature and irregular topology.

25. 4/12/2012 25 ILM - Effects The wave swells and forms part of the ocean simulation It collides with the Andrea Gail a rigid body object placed in the ocean simulation The wave impacts and breaks over the boat the particle system emits millions of particles

26. 4/12/2012 26 ILM - Effects The Wave spreads out The particles obey the dynamics of surface tension versus outside forces Some of the splash becomes mist and blows off in the wind An aerodynamic simulation is done to calculate the wind forces Most of the water falls onto the deck of the Andrea Gail and trickles back into the ocean, creating foam The particles follow the rules of the collision model upon reaching the surface of the Andrea Gail object

27. 4/12/2012 27 ILM - The Andrea Gail Set up as a rigid body with a collision model

28. 4/12/2012 28 ILM - Effects Splash created by the boat crashing into a wave Particle model of boat’s movement in the water

29. 4/12/2012 29 The Perfect Storm Run-off from a wave crashing over the boat  Boat's lighting model

30. 4/12/2012 30 Particle System - Touch Up’s The amount of spray coming may not be as heavy as the director wishes Emitters Inserting particle sources is a common way to create environmental effects, such as fog and mist. Shaders Determine how an object will appear as a function of light, density and surface color Just because the simulations follow the complicated laws of fluid dynamics the rendered scenes may not always look right or be what the director intendedJust because the simulations follow the complicated laws of fluid dynamics the rendered scenes may not always look right or be what the director intended

31. 4/12/2012 31 ILM - Adding the Actors Shot in a wave pool with a blue screen ILM later added the rest of the scene The final scene included the CG water, sky, helicopter and diver

32. 4/12/2012 32 ILM - The End Shot

33. 4/12/2012 33 I believe it