Purpose

FLIP Liquid simulates liquid particles on a velocity grid. Use it for pours, splashes and pooling. Its whitewater modes add spray, surface foam or bubbles, with separate or combined particle outputs.

Use

Place FLIP Liquid in the Voro menu’s Geometry view, under Solvers. Start with Seed Source set to Fill Box, Resolution at 96 and Bound Size at 2. Keep the fill inside the domain. This gives you a finite amount of liquid to test before adding an emitter.

For a continuous pour, choose Empty (Emitter Only), turn Liquid Emit On on and set a positive Liquid Emit Rate. A starting rate of 1000 makes it easy to check the emitter’s position and direction. Reset after changing the seed setup. Input POP is available for both seeding and emission; connect your points to the geometry input and choose it in the appropriate Source menu.

Inputs and outputs

The geometry input supplies seed or emitter points. On Resources, add a Connections row, choose the sdf input in Type and select an SDF Collider resource. Use a velocity row for a Force Field or another solver’s velocity, and xforms for moving-body transforms.

The named outputs carry liquid positions P, velocity v, id, Cd and type. Foam outputs depend on Foam Mode and Foam Output. Density and velocity grids require Publish Grid Fields (liquid), which is off by default. Contact publication has its own toggle and capacity. These are simulation resources; liquid points do not become a meshed Path Trace surface automatically.

Controls

• Simulate pauses or advances the simulation. Reset restarts it from the seed setup. Auto-Rebuild on Build Params applies structural edits as you make them; turn it off to collect edits, then press Rebuild when Status shows REBUILD PENDING.
• Resolution sets grid detail within Max Resolution. Bound Size and Bound Center place that grid. Keep the domain close to the liquid before raising resolution.
• FLIP Blend starts at 0.92. Moving toward 0 gives the more damped PIC behavior. Pressure Iterations starts at 40; Dt starts near 1/60 second.
• Water Amount scales seeding and emission. Liquid Viscosity, Surface Tension and Collider Adhesion change the liquid response; add them after checking the basic pour.
• Velocity Field Coupling starts at 0. A connected wind field needs a positive coupling value to affect the liquid.
• Foam Mode starts off. Choose Separate output to keep whitewater distinct, or Combined to include it with liquid and distinguish particles by type. Whitewater Max Particles and Lifetime limit how much persists.

Notes

Max Particles is a pool limit. At Max Particles chooses whether an emitter stops or recycles the oldest particles. Display Max Points limits presentation separately.

Grid fields and whitewater add work and storage. Leave both off while establishing the liquid motion, then enable the outputs you need.

Ports

Inputs

• geometry points
• sdf sdf collider
• velocity velocity field
• xforms transforms

Outputs

• P points
• v points
• id points
• Cd points
• type points
• foam points
• foamtype points
• density density field
• velocity velocity field
• contact contacts

Parameters

FLIP Liquid

Auto-Rebuild on Build Params (Autorebuild) Toggle op('flip').par.Autorebuild

Default:

On

Options:

Off, On

Rebuild (Rebuildnow) Pulse op('flip').par.Rebuildnow

Default:

None

Simulate (Simulate) Toggle op('flip').par.Simulate

Default:

On

Options:

Off, On

Reset (Resetsolver) Pulse op('flip').par.Resetsolver

Default:

None

Outputs

Liquid Resources (Hdrres) Str op('flip').par.Hdrres

Read only.

Default:

"" (Empty String)

Liquid Points Resource (Liquidname) Str op('flip').par.Liquidname

Default:

liquid_pts

Density Output Resource (Densityname) Str op('flip').par.Densityname

Default:

smoke_density

Velocity Output Resource (Velocityname) Str op('flip').par.Velocityname

Default:

smoke_vel

Publish Grid Fields (liquid) (Liquidfields) Toggle op('flip').par.Liquidfields

Default:

Off

Options:

Off, On

Display Max Points (Displaymaxpoints) Int op('flip').par.Displaymaxpoints

Default:

1048576

Range:

1 to 4194304

Display Particle Pscale (liquid) (Particlepscale) Float op('flip').par.Particlepscale

Default:

0.05

Range:

0 to 0.5

Domain

Max Resolution (pool) (Maxresolution) Int op('flip').par.Maxresolution

Default:

128

Range:

16 to 256

Resolution (Resolution) Int op('flip').par.Resolution

Default:

96

Range:

8 to 256

Bound Size (cube) (Boundsize) Float op('flip').par.Boundsize

Default:

2

Range:

0.1 to 8

Bound Center X (Boundcenterx) Float op('flip').par.Boundcenterx

Default:

0

Range:

-10 to 10

Bound Center Y (Boundcentery) Float op('flip').par.Boundcentery

Default:

0

Range:

-10 to 10

Bound Center Z (Boundcenterz) Float op('flip').par.Boundcenterz

Default:

0

Range:

-10 to 10

Solver

Dt (Dt) Float op('flip').par.Dt

Default:

0.0166667

Range:

0.0001 to 0.5

Liquid

Pressure Iterations (Iterations) Int op('flip').par.Iterations

Default:

40

Range:

1 to 200

Gravity (Gravity) Float op('flip').par.Gravity

Default:

9.8

Range:

0 to 30

FLIP Blend (0=PIC) (Flipness) Float op('flip').par.Flipness

Default:

0.92

Range:

0 to 1

CFL Speed Clamp (cells/step) (Cflclamp) Float op('flip').par.Cflclamp

Default:

3

Range:

0.5 to 8

Liquid Viscosity (Liquidviscosity) Float op('flip').par.Liquidviscosity

Default:

0

Range:

0 to 10

Liquid Cohesion (Liquidcohesion) Float op('flip').par.Liquidcohesion

Default:

0

Range:

0 to 30

Surface Tension (Surfacetension) Float op('flip').par.Surfacetension

Default:

0

Range:

0 to 30

Collider Adhesion (wetting) (Liquidadhesion) Float op('flip').par.Liquidadhesion

Default:

0

Range:

0 to 10

Spray Drag (Liquiddrag) Float op('flip').par.Liquiddrag

Default:

0

Range:

0 to 10

Velocity Field Coupling (vel:) (Windcoupling) Float op('flip').par.Windcoupling

Default:

0

Range:

0 to 1000

Volume Restore (Volumerestore) Float op('flip').par.Volumerestore

Default:

0

Range:

0 to 10

Liquid Particle Cell Radius (Particlecellradius) Float op('flip').par.Particlecellradius

Default:

0.5

Range:

0.5 to 4

Liquid Volume Mult (live) (Simsize) Float op('flip').par.Simsize

Default:

1

Range:

0.01 to 8

Rebuild Grid (Rebuild) Pulse op('flip').par.Rebuild

Default:

None

Reset Fields (Resetfields) Pulse op('flip').par.Resetfields

Default:

None

Seed

Max Particles (pool) (Maxparticles) Int op('flip').par.Maxparticles

Default:

1048576

Range:

4096 to 4194304

Seed Source (Seedsource) Menu op('flip').par.Seedsource

Default:

0

Options:

Fill Box, Input POP, Empty (Emitter Only)

Liquid Fill Center X (Fillcenterx) Float op('flip').par.Fillcenterx

Default:

-0.6

Range:

-10 to 10

Liquid Fill Center Y (Fillcentery) Float op('flip').par.Fillcentery

Default:

-0.4

Range:

-10 to 10

Liquid Fill Center Z (Fillcenterz) Float op('flip').par.Fillcenterz

Default:

0

Range:

-10 to 10

Liquid Fill Size X (Fillsizex) Float op('flip').par.Fillsizex

Default:

0.7

Range:

0.01 to 10

Liquid Fill Size Y (Fillsizey) Float op('flip').par.Fillsizey

Default:

1.1

Range:

0.01 to 10

Liquid Fill Size Z (Fillsizez) Float op('flip').par.Fillsizez

Default:

1.2

Range:

0.01 to 10

Water Amount (seed/emit) (Wateramount) Float op('flip').par.Wateramount

Default:

1

Range:

0.01 to 16

Reseed Liquid (Reseed) Pulse op('flip').par.Reseed

Default:

None

Coupling

Coupling (Hdrcouple) Str op('flip').par.Hdrcouple

Read only.

Default:

"" (Empty String)

Publish Contact Set (Publishcontacts) Toggle op('flip').par.Publishcontacts

Default:

On

Options:

Off, On

Max Published Contacts (Contactmaxpublish) Int op('flip').par.Contactmaxpublish

Default:

65536

Range:

1024 to 4194304

Contact Mass Scale (Contactmassscale) Float op('flip').par.Contactmassscale

Default:

1

Range:

0.001 to 1000

Emitter

Liquid Emit On (Liquidemiton) Toggle op('flip').par.Liquidemiton

Default:

Off

Options:

Off, On

Emitter Source (Emittersource) Menu op('flip').par.Emittersource

Default:

0

Options:

Sphere, Box, Input POP

Liquid Emit X (Liquidemitx) Float op('flip').par.Liquidemitx

Default:

0

Range:

-10 to 10

Liquid Emit Y (Liquidemity) Float op('flip').par.Liquidemity

Default:

0.3

Range:

-10 to 10

Liquid Emit Z (Liquidemitz) Float op('flip').par.Liquidemitz

Default:

0

Range:

-10 to 10

Emitter Size X (Liquidemitsizex) Float op('flip').par.Liquidemitsizex

Default:

0.24

Range:

0.001 to 10

Emitter Size Y (Liquidemitsizey) Float op('flip').par.Liquidemitsizey

Default:

0.24

Range:

0.001 to 10

Emitter Size Z (Liquidemitsizez) Float op('flip').par.Liquidemitsizez

Default:

0.24

Range:

0.001 to 10

Liquid Emit Rate (Liquidemitrate) Float op('flip').par.Liquidemitrate

Default:

0

Range:

0 to 50000

Liquid Emit Vx (Liquidemitvx) Float op('flip').par.Liquidemitvx

Default:

0

Range:

-50 to 50

Liquid Emit Vy (Liquidemitvy) Float op('flip').par.Liquidemitvy

Default:

0

Range:

-50 to 50

Liquid Emit Vz (Liquidemitvz) Float op('flip').par.Liquidemitvz

Default:

0

Range:

-50 to 50

Input Velocity Attribute (Inputvelattr) Str op('flip').par.Inputvelattr

Default:

v

Input Velocity Scale (Inputvelscale) Float op('flip').par.Inputvelscale

Default:

1

Range:

-100 to 100

Input Velocity Add (Inputveladdx) Float op('flip').par.Inputveladdx

Default:

0

Range:

-50 to 50

Input Velocity Add Y (Inputveladdy) Float op('flip').par.Inputveladdy

Default:

0

Range:

-50 to 50

Input Velocity Add Z (Inputveladdz) Float op('flip').par.Inputveladdz

Default:

0

Range:

-50 to 50

At Max Particles (Emitoverflow) Menu op('flip').par.Emitoverflow

Default:

0

Options:

Stop Emitting, Recycle Oldest

Foam

Foam Mode (Foammode) Menu op('flip').par.Foammode

Default:

0

Options:

Off, Whitewater (spray+foam+bubbles), Bubbles (trapped air), Carbonation / Beer (nucleation), Boil (bottom-up)

Foam Output (Foamoutput) Menu op('flip').par.Foamoutput

Default:

0

Options:

Separate (<liquid>_foam buffer), Combined (into <liquid> + _type)

Whitewater Max Particles (Whitewatermax) Int op('flip').par.Whitewatermax

Default:

262144

Range:

256 to 4194304

Foam Generation Rate (Foamgen) Float op('flip').par.Foamgen

Default:

2

Range:

0 to 10

Wave Crest / Spray Weight (Foamcrest) Float op('flip').par.Foamcrest

Default:

1

Range:

0 to 4

Trapped Air (churn) Weight (Foamtrapped) Float op('flip').par.Foamtrapped

Default:

0.8

Range:

0 to 4

Churn Threshold (Foamthreshold) Float op('flip').par.Foamthreshold

Default:

0.5

Range:

0 to 1

Nucleation (carbonation) (Foamnucleation) Float op('flip').par.Foamnucleation

Default:

0

Range:

0 to 20

Foam Scale (cells) (Foamscale) Float op('flip').par.Foamscale

Default:

0.5

Range:

0 to 4

Whitewater Lifetime (s) (Foamlifetime) Float op('flip').par.Foamlifetime

Default:

2

Range:

0.1 to 8

Surface Foam Decay (1/s) (Foamdecay) Float op('flip').par.Foamdecay

Default:

1

Range:

0 to 10

Bubble Buoyancy Lift (Foambuoyancy) Float op('flip').par.Foambuoyancy

Default:

1

Range:

0 to 10

Bubble/Foam Drag (Foamdrag) Float op('flip').par.Foamdrag

Default:

4

Range:

0 to 15

Color

Liquid Base Color (Basecolorr) Float op('flip').par.Basecolorr

Default:

0.2

Range:

0 to 1

Liquid Base Color G (Basecolorg) Float op('flip').par.Basecolorg

Default:

0.45

Range:

0 to 1

Liquid Base Color B (Basecolorb) Float op('flip').par.Basecolorb

Default:

0.9

Range:

0 to 1

Liquid Color Speed Brightness (Colorspeed) Float op('flip').par.Colorspeed

Default:

0

Range:

0 to 1

Liquid Color Speed Normalize (Colorspeedmax) Float op('flip').par.Colorspeedmax

Default:

4

Range:

0.01 to 20

Spray Color (Spraycolorr) Float op('flip').par.Spraycolorr

Default:

1

Range:

0 to 1

Spray Color G (Spraycolorg) Float op('flip').par.Spraycolorg

Default:

1

Range:

0 to 1

Spray Color B (Spraycolorb) Float op('flip').par.Spraycolorb

Default:

1

Range:

0 to 1

Foam Color (Foamcolorr) Float op('flip').par.Foamcolorr

Default:

0.92

Range:

0 to 1

Foam Color G (Foamcolorg) Float op('flip').par.Foamcolorg

Default:

0.96

Range:

0 to 1

Foam Color B (Foamcolorb) Float op('flip').par.Foamcolorb

Default:

1

Range:

0 to 1

Bubble Color (Bubblecolorr) Float op('flip').par.Bubblecolorr

Default:

0.7

Range:

0 to 1

Bubble Color G (Bubblecolorg) Float op('flip').par.Bubblecolorg

Default:

0.82

Range:

0 to 1

Bubble Color B (Bubblecolorb) Float op('flip').par.Bubblecolorb

Default:

1

Range:

0 to 1