ocean wave simulation - western washington universitywehrwes/courses/... · question: what causes a...
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Ocean Wave SimulationRobin Cosbey and Chloe Dawson
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Wave Properties
NVIDIA WaveWorks
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Wave Dynamics
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Wave Dynamics
Deep-water
Depth ≥ 1/2 L
Intermediate
1/2 L > Depth > 1/20 L
Shallow-water
Depth ≤ 1/20 L
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Wave GenerationQuestion: What causes a wave?
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Wave GenerationQuestion: What causes a wave?
> Wind
> Boats
> Earthquakes
> Gravitational pull
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Wave Functions
Spinoff Studio
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Models
Elevation Model
Heightmap - 2D regular grid, each cell represents the surface height
Volumetric Model
Voxel - 3D regular grid, each cell is assigned a material index
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Simplex Noise Similar to Perlin noise
Generates a height map which can be applied to other wave functions to provide a more realistic texture
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Navier-StokesMultiple equations describing motion of viscous fluids
Often used to capture breaking waves near shore
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Gerstner Waves
Modified sine wave with sharper peaks and flatter valleys
Controlled by manipulating amplitude, direction and speed
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Gerstner Waves
Particles of water are described with circular/elliptical stationary orbits
Moving vertices toward each crest forms sharper crests
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Gerstner Waves
Question: How can we make this more realistic?
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Gerstner Waves
Question: How can we make this more realistic?
> Add waves with varying properties
4 waves!
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Flags and Waves - SIGGRAPH 1986
“A Simple Model of Ocean Waves”
Based on Gerstner Waves
A parametric surface made up of position at rest (x0 , y0) and time
Incorporates effects of wave direction, depth and shore distance
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Fast Fourier Transforms Statistical model where wave height is considered a random variable of horizontal position and time, h(x, t)
Reasonable representation of naturally occuring wind-waves
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Ocean Phenomena
OpenGL
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Foam and Spray
1. Semi-transparent textures
Foam spawns near tops of big waves
For a given vertex:
Compute difference in slope between vertex and neighbors
If difference < threshold:Increase foam amount
Otherwise Decrease foam amount
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Foam and Spray
2. Particle systems
More realistic but more costly
Spray subsystems are generated based on velocity of water particles and wave amplitude
Result is rendered as cloud points
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Radiosity
L_above = reflection(L_sun + L_sky) + transmission(L_under)
Specular reflection from direct sunlight and skylight
Transmission of incident light through surface
(More reflection / refraction from previously reflected / refracted light)
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Specular ReflectionFor a ray intersecting the surface, the direction of the reflected ray depends only on the incident direction and the surface normal
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Caustics
Snell’s Law determines how refracted light will bend the trajectory
As light advances deeper into the water the intensity attenuates
Eventually light strikes the ocean floor
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Color
Based on reflected and refracted light
Opacity of waterFunction of depth Viewing angle
Tint of reflectionEnvironment mapping
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Thank you! Questions?
Unity: Crest