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Vortex Fluid Structure For Smoke ControlPowerPoint Presentation

Vortex Fluid Structure For Smoke Control

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### Vortex Fluid StructureFor Smoke Control

Contributions

Alexis Angelidis (1)

Fabrice Neyret (2)

Karan Singh (1)

Derek Nowrouzezahrai (1)

(1): DGP, U of Toronto

(2): Evasion-GRAVIR / IMAG-INRIA

Motivation

- Fluid Animation: smoke, clouds, fire, explosion, splashes, sea…
- Simulation vs Animation

[ Areté Entertainment, inc. 96]

[ LOTR ]

Motivation

- Fluid Animation: smoke, clouds, fire, explosion, splashes, sea…
- Simulation vs Animation
- Approaches to control:
- Phenomenological, limited
- Fake forces
- Control by keyframing ‘shapes’

[ Areté Entertainment, inc. 96]

[ LotR ]

Motivation

[Treuille et al.03],[McNamara et al.04],[Fattal et al.04]

Most related work

- Density field given at keyframes
- Solver between frames
What we want

- No hand-drawn smoke
- Natural control

key2

key1

[McNamara et al.04]

Background [AN05]

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

‘‘Chart of methods for numerical fluid simulation’’

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

3D

field

velocity v

Rotation in rad s-1

translation in m s-1

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

velocity v

Curl

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

velocity v

BIOT-SAVART

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

Dynamics :

Eulerian

The flow modifies quantities

held at static positions

Lagrangian

The flow carries floaters that

hold the quantities

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

Eulerian

Lagrangian

in grid

at particle

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

NAVIER-STOKES

( incompressible )

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

VORTICITY EQUATION

( inviscid )

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

No diffusion

Implicit incompressibility

compact

Unbounded

…

Easy boundary conditions

Easy extra differential eqn

…

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

Vorticity:

Vortex particle advected, vector stretched

vorticity moves as material lines

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

Vorticity:

Our primitive = curves

= tangent

Background

Velocity

Vorticity

moving

quantity

representation

popular

Eulerian

our

method

Lagrangian

Density:

Dedicated particles

- passive floaters

- for rendering

- only where smoke is

Density:

a quantity at nodes

Lagrangian primitives

- Curves carry the vorticity
- Each local vortex induces a weighted rotation

Lagrangian primitives

- Curves carry the vorticity
- Each local vortex induces a weighted rotation

Method of simulation

- Vortex particles (for motion) organized as curves. = tangent
- Smoke particles (for visualisation)
- Curves carry vortices
- Vortices induce a velocity field
- velocity field deforms curves & smoke
At every step:

- Advect the curves
- Stretch
- Advect the smoke

Method of simulation

- Vortex particles (for motion) organized as curves. = tangent
- Smoke particles (for visualisation)
- Curves carry vortices
- Vortices induce a velocity field
- velocity field deforms curves & smoke
At every step:

- Advect the curves
- Stretch
- Advect the smoke

Method of simulation

- Vortex particles (for motion) organized as curves. = tangent
- Smoke particles (for visualisation)
- Curves carry vortices
- Vortices induce a velocity field
- velocity field deforms curves & smoke
At every step:

- Advect the curves
- Stretch
- Advect the smoke

Contributions

- A new representation of vortex curves
Compact, stable, controlable motion primitives

- Controls of the motion primitives
- Fast ‘‘noise’’ for fake turbulence details

Contributions

- A new representation of vortex curves
Compact, stable, controlable motion primitives

- Controls of the motion primitives
- Fast ‘‘noise’’ for fake turbulence details

Deformation of curves previous approach [AN05]

If not refined:

undersampling

Polygon

If refined:

too complex

Strategy to control complexity

New representation

- Solution: harmonic analysis of coordinates

x

= in y

z

a pair of coefficients for each harmonic

- Reference frame: best ellipsoid

Complexity control

- Curves described by :
- Frame o ex ey ez
- Frequencies <cx cy cz>1..N

Synthesis

Advection

Analysis

New representation

- Solution: harmonic analysis of coordinates

x

= in y

z

a pair of coefficients for each harmonic

ez

ey

- Reference frame: best ellipsoid

o

ex

Complexity control

- Curves described by :
- Frame o ex ey ez
- Frequencies <cx cy cz>1..N

Synthesis

Advection

Analysis

New representation

- Solution: harmonic analysis of coordinates

x

= in y

z

a pair of coefficients for each harmonic

ez

ey

- Reference frame: best ellipsoid

o

ex

Complexity control

- Curves described by :
- Frame o ex ey ez
- Frequencies <cx cy cz>1..N

Synthesis

Advection

Analysis

New representation

- Solution: harmonic analysis of coordinates

x

= in y

z

a pair of coefficients for each harmonic

ez

ey

- Reference frame: best ellipsoid

o

ex

Complexity control

- Curves described by :
- Frame o ex ey ez
- Frequencies <cx cy cz>1..N

Synthesis

Advection

Analysis

ez

ey

…

o

ex

Meaning of description- ez points towards moving direction

- Frequencies cx cy cz give texture to the flow

- Thickness

Contributions

- A new representation of vortex curves
Compact, stable, controlable motion primitives

- Controls of the motion primitives
- Fast ‘‘noise’’ for fake turbulence details

without

with

ez

ey

<cx cy cz>1..N

…

o

ex

Control- direction: align ez with tangent
- Targets:
- Twisting smoke: spin vortices around ez
- Edit, delete …
- Modulate cx cy cz to texturethe flow

without

with

ez

ey

<cx cy cz>1..N

…

o

ex

Control- direction: align ez with tangent
- Targets:
- Twisting smoke: spin vortices around ez
- Edit, delete …
- Modulate cx cy cz to texturethe flow

without

with

ez

ey

<cx cy cz>1..N

…

o

ex

Control- direction: align ez with tangent
- Targets:
- Twisting smoke: spin vortices around ez
- Edit, delete …
- Modulate cx cy cz to texturethe flow

How to control

- One cannot just translate the curves: the smoke does not follow

- Solution: paddle(servoing )

ez

ey

o

ex

- A new representation of vortex curves
Compact, stable, controlable motion primitives

- Controls of the motion primitives
- Fast ‘‘noise’’ for fake turbulence details

noise = extra vortex particles

advected in the flow, no stretch

Costly (needs a lot)

Source, sampling

Tiled vortex noise:

noise layer =

separate simulation, in toroidal space

Tiled in space

Additional evolving velocity field

Noise: fake turbulence detailsnoise = extra vortex particles

advected in the flow, no stretch

Costly (needs a lot)

Source, sampling

Tiled vortex noise:

noise layer =

separate simulation, in toroidal space

Tiled in space

Additional evolving velocity field

Noise: fake turbulence detailsnoise = extra vortex particles

advected in the flow, no stretch

Costly (needs a lot)

Source, sampling

Tiled vortex noise:

noise layer =

separate simulation, in toroidal space

Tiled in space

Additional evolving velocity field

Noise: fake turbulence detailsContributions

- A new representation of vortex curves
Compact, stable, controlable motion primitives

- Controls of the motion primitives
- Fast ‘‘noise’’ for fake turbulence details
- Velocity cache, rendering

Octree cache

- Velocity computed at octree leaves + inbetween interpolation

- Velocity computed at every smoke particle &every vorticity curve sample

Octree cache

- Velocity computed at octree leaves + inbetween interpolation

- Velocity computed at every smoke particle &every vorticity curve sample

Rendering

- Thick smoke: plain particles
- Thin smoke: adaptive particles[AN05]
- accumulate stretching

Results - video

fpsForest fire Genie&lamp Walkthrough Fly

Modeler quality5 12 5 18

Final rendering quality0.54 0.2 1. 0.37

Conclusion

Vorticity filaments:

- Compact, high-res, fast
- Good handles to manipulate a fluid
- Can be manipulated interactively or post-
Future work:

- Split/merge
- High-quality collisions
- 2-phase, buoyancy, …

Coupling with grids

Rendering

- Thin smoke behaves like a surface

Lagrangian primitives

- Curves carry the vorticity
- Each vortex induces a weighted rotation

Effect of one vortex on ashape :

Checkpoint

- With control

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