Advected texturesAdvected textures

Fabrice Neyret

EVASION - GRAVIR / IMAG - INRIA

Grenoble, France

Purpose: amplifying fluid simulationPurpose: amplifying fluid simulation

Purpose: amplifying fluid simulationPurpose: amplifying fluid simulation

Why not simply increase resolution ?Why not simply increase resolution ?

Cost: N log(N) / time step with N=1000^3

Storage

Problems with CFD for CG [Lamorlette&Foster 02]

Unknown small scale phenomena vs artist desires + phenomenological knowledge

Why not simply increase resolution ?Why not simply increase resolution ?

Cost: N log(N) / time step with N=1000^3

Storage

Problems with CFD for CG [Lamorlette&Foster 02]

Unknown small scale phenomena vs artist desires + phenomenological knowledge

Why not simply increase resolution ?Why not simply increase resolution ?

Cost: N log(N) / time step with N=1000^3

Storage

Problems with CFD for CG [Lamorlette&Foster 02]

Unknown small scale phenomena vs artist desires + phenomenological knowledge

Why not simply increase resolution ?Why not simply increase resolution ?

Cost: N log(N) / time step with N=1000^3

Storage

Problems with CFD for CG [Lamorlette&Foster 02]

Unknown small scale phenomena vs artist desires + phenomenological knowledge

Advecting texturesAdvecting textures

= Advecting u,v [Max&Becker 96, Stam 99]

Regeneration blending 3 dephased textures

(illusion of motion)

latency = life duration

Problems with texture advectionProblems with texture advection

Choosing the latency

Blending textures

Sub-animation

11

22

33

Problems with texture advectionProblems with texture advection

Choosing the latency

Blending textures

Sub-animation

11

22

33

Problems with texture advectionProblems with texture advection

Choosing the latency

Blending textures ghosting effects

Sub-animation

11

22

33

Problems with texture advectionProblems with texture advection

Choosing the latency

Blending textures

Sub-animation

11

22

33

Problems with texture advectionProblems with texture advection

Choosing the latency

Blending textures

Sub-animation

11

22

33

1.1. Advecting textures1.1. Advecting textures

A latency value is ok for a range of velocities (V) bad motion illusion if V < texture stretching if V >

1. Advecting textures1. Advecting textures

Adapting latency locally Layers of given latency + masks

Local criterion

– cumulated deform = particle integral of ||

– Target deform d*

1. Advecting textures1. Advecting textures

Adapting latency locally Layers of given latency + masks

Local criterion

– cumulated deform = particle integral of ||

– Target deform d*

Layer 1: lat1

Layer 2: lat2 (>lat1)

Layer 3: lat3 (>lat2)

1. Advecting textures1. Advecting textures

Adapting latency locally Layers of given latency + masks

Local criterion

– cumulated deform = particle integral of ||

– Target deform d*

1 2 3

2.2. Blending textures2.2. Blending textures

Image textures

Procedural textures

2. Blending textures: image textures2. Blending textures: image textures

What to do ? (morphing ?)

2. Blending textures: procedural textures2. Blending textures: procedural textures

Our solution:

3.3. Sub-animation3.3. Sub-animation

Flownoise [Perlin&Neyret 01]

3. Sub-animation3. Sub-animation

Flownoise for sub-scales

rotations vorticity spectrum

Kolmogorov cascade

3. Sub-animation3. Sub-animation

Flownoise for sub-scales

rotations vorticity spectrum < >

Kolmogorov cascade

3. Sub-animation3. Sub-animation

Flownoise for sub-scales

rotations vorticity spectrum < >

Kolmogorov cascade

k = k =

EE

kk00 kk

sub-gridsub-gridCFDCFD

microscalemicroscale

3. Sub-animation3. Sub-animation

Vorticity energy transfer through scales

distribution law for ( power law ) only needs to scale it ( estimate )

Our case:

heterogeneous fluid ( locality no Fourier ) not at equilibrium ( transfer delay time ) user control

relaxation

< >< >

3. Sub-animation3. Sub-animation

Vorticity energy transfer through scales

distribution law for ( power law ) only needs to scale it ( estimate )

Our case:

heterogeneous fluid ( locality no Fourier ) not at equilibrium ( transfer delay time ) user control

relaxation

(user-defined parameters k and k )

< >< >

ResultsResults

ConclusionConclusion

Mixing lo-res CFD and hi-res animated texture: A model efficient & controllable

Future work:– 3D applications: detailed clouds & avalanches– Better flownoise control– Manage empty space– Hardware procedural shader

Advected texturesAdvected textures

Fabrice Neyret

EVASION - GRAVIR / IMAG - INRIA

(Grenoble, France)

Sub-animation parametersSub-animation parameters

parameters k and k:

small : reactive high : inertial

small : viscous high : light

1. Advecting textures1. Advecting textures

3D 3D