Phenomenological Simulation of Brooks

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Phenomenological Simulation of Brooks

• Fabrice Neyret Nathalie Praizelin
• iMAGIS / GRAVIR - IMAG

iMAGIS is a joint project of CNRS, INRIA,
INPG and UJF.
http//www-imagis.imag.fr/
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If CFD had to be used
(Navier-Stokes)
FM96,97,...

• Very thin resolution, large domain ( and
  stability ? very small dt )
• Very non-linear equations (shockwaves, surf.
  tension)
• ? Hard and long system solving
• Unknown parameters (e.g. boundary conditions)
• Visible features are emerging phenomena ?
  Hard to control
• while
• Water motion is not directly visible
• Strong a priori knowledge on the result
• Users want some control

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If surface wave simulation had to be used
FR86,P86,GS97

• Very thin resolution, large domain
• Very non-linear equations (waves trigger waves)
• Hard and long system solving
• while
• Strong a priori knowledge on the result

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If Fourier synthesis had to be used
MWM87,TDG00,Areté

• Very thin resolution, large domain
• Non-linear phenomena
• Non uniform wave propagation(variable depth,
  obstacles)
• ? Statistical models are helpless
• while
• Strong a priori knowledge on the result
• Users want some control

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Relying on phenomenological simulation

• Primitives based
• Geometric construction of visual features
• Choice of the primitives of visual interest
• User can control the primitives
• Vector primitives independent from
  rendering resolution
• Fast, high resolution, large domain

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• Phenomena that are out of scope

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Wave theory
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Wave theory
capillary waves cg gt cw
shallow water cg cw
gravity waves cg lt cw
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Typology of stationary waves
non dispersive case cg cw c ? shockwave
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Froude waves - shockwaves calculation
(Froude number)
(slope)
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Froude waves - shockwaves calculation
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The chosen primitives
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Our approach

• 1. Get a stationary velocity field (low res is
  ok)
• 2. Build the primitives skeletons
• 3. Add field perturbations WH91
• 4. ( Build a surface and render )

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1. Get a stationary velocity field
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1. Get a stationary velocity field
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1. Get a stationary velocity field
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1. Get a stationary velocity field
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2. Build the primitives skeletons
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2. Build the primitives skeletons
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3. Add field perturbations

• WH91
• Small support fields (vortex,source)attached on
  particles (passive floaters)

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3. Add field perturbations

• A perturbation needs time to propagate
• We cannot simply apply the static construction !
• A node moves if
• V changes locally
• the previous node has moved

perturb V gtgt
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3. Add field perturbations
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Conclusion - limitations - future work

• A real-time simulation of (some) animated visual
  features of brooks !
• Vectorial construction (no grid sampling)
• Perturbations can be random, procedural (von
  Karman),or user generated.
• Fade and stop the primitives.
• Adaptive capillary ripples.
• Define a rendering method ! (producing a surface
  ?)
• Hydraulic jumps, foam, ...

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Phenomenological Simulation of Brooks

• Fabrice Neyret Nathalie Praizelin
• iMAGIS / GRAVIR - IMAG

iMAGIS is a joint project of CNRS, INRIA,
INPG and UJF.
http//www-imagis.imag.fr/
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• Le détail des mouvements est complexe

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Exploite-t-on toute la connaissance disponible ?

• Il y a de grandes régularités dans les scènes
  naturelles !