Purpose

Gas / Smoke moves density, temperature and velocity through a grid. Buoyancy raises hot gas, density weight pulls it down, and dissipation fades the fields over time. Optional combustion adds fuel burning, heat and soot.

Use

Place Gas / Smoke in the Geometry view, under Solvers. Start with the built-in emitter on, Resolution at 96 and Bound Size at 2. Its default position is below the domain center. Keep Combustion off while adjusting the smoke plume.

For point-driven emission, select a points resource in Resources > Connections and raise Points Density Rate or Points Temperature Rate. Both start at 0, so connecting points alone does not emit smoke. Turn off the built-in emitter if you want only the point source.

Inputs and outputs

The geometry input accepts incoming geometry. Connections accepts sdf, points, velocity and xforms resources for obstacles, point emission, external flow and moving bodies.

The outputs are density, velocity, temperature, lookid and color fields. Connect velocity to Field Lines to inspect flow, or to another solver’s velocity input. Emitter Look Class stamps a field value; it does not select a finished rendered style. The current Path Trace scene workflow collects polygonal geometry and does not render these smoke fields directly.

Controls

• Simulate controls advancement; Reset restarts the fields. Auto-Rebuild on Build Params and Rebuild control when structural changes take effect. Reset Fields clears the field state.
• Resolution and the domain bounds set voxel size. Max Resolution reserves the grid pool. Begin with the default 40 Pressure Iterations before increasing grid detail.
• Advection offers MacCormack for sharper transport and Semi-Lagrangian for a more conservative result.
• Buoyancy responds to temperature above Ambient Temperature. Density Weight adds sinking. Density and Temperature Dissipation control how long the plume remains.
• Vorticity Confinement adds curl to the flow. Turbulence adds animated curl noise; start with a small amplitude so you can still see the emitter’s motion.
• Combustion On enables fuel burning. Fuel Emit Rate, Ignition Temperature, Burn Rate, Heat Release and Soot Yield control the burn. Check emitter temperature against ignition when no burning appears.
• Force Field Strength scales a connected velocity resource. Show Preview, Preview Density and Preview Length affect the field preview, not the simulation grid.

Notes

The node’s velocity preview shows flow direction. It is not a smoke beauty render. Use a separate Field Lines node when you want its speed colors and length controls.

A denser three-dimensional grid increases memory use on all three axes. Keep the bounds around the plume and check emission and dissipation before raising Resolution.

Ports

Inputs

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

Outputs

• density density field
• velocity velocity field
• temperature temperature field
• lookid look id field
• color color field
• preview lines
• preview_cd lines

Parameters

Gas / Smoke

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

Default:

On

Options:

Off, On

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

Default:

None

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

Default:

On

Options:

Off, On

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

Default:

None

Preview

Show Preview (Previewshow) Toggle op('gas').par.Previewshow

Default:

On

Options:

Off, On

Preview Density (Previewdensity) Int op('gas').par.Previewdensity

Default:

12

Range:

2 to 48

Preview Length (cells) (Previewlength) Float op('gas').par.Previewlength

Default:

0.6

Range:

0 to 2

Outputs

Smoke Resources (Hdrsmokeres) Str op('gas').par.Hdrsmokeres

Read only.

Default:

"" (Empty String)

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

Default:

smoke_density

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

Default:

smoke_vel

Temperature Output Resource (Temperaturename) Str op('gas').par.Temperaturename

Default:

smoke_temp

Look-Class Output Resource (Lookidname) Str op('gas').par.Lookidname

Default:

smoke_lookid

Domain

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

Default:

128

Range:

16 to 256

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

Default:

96

Range:

8 to 256

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

Default:

2

Range:

0.1 to 8

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

Default:

0

Range:

-10 to 10

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

Default:

0

Range:

-10 to 10

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

Default:

0

Range:

-10 to 10

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

Default:

None

Solver

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

Default:

0.0166667

Range:

0.0001 to 0.5

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

Default:

40

Range:

1 to 200

Pressure Over-Relaxation (SOR) (Soromega) Float op('gas').par.Soromega

Default:

1

Range:

1 to 1.95

Advection (Advection) Menu op('gas').par.Advection

Default:

0

Options:

MacCormack (sharp), Semi-Lagrangian (conservative)

Solid Boundary (Boundary) Menu op('gas').par.Boundary

Default:

0

Options:

Free Slip, No Slip

Moving Boundary Slip (Boundaryslip) Float op('gas').par.Boundaryslip

Default:

0

Range:

0 to 1

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

Default:

None

Coupling

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

Read only.

Default:

"" (Empty String)

Clear Density In Bodies (Bodyclear) Toggle op('gas').par.Bodyclear

Default:

On

Options:

Off, On

Forces

Buoyancy (temperature) (Buoyancy) Float op('gas').par.Buoyancy

Default:

1.2

Range:

0 to 5

Density Weight (sink) (Densityweight) Float op('gas').par.Densityweight

Default:

0.08

Range:

0 to 1

Ambient Temperature (Ambient) Float op('gas').par.Ambient

Default:

0

Range:

-20 to 20

Vorticity Confinement (Vorticity) Float op('gas').par.Vorticity

Default:

0.35

Range:

0 to 2

Density Dissipation (Dissipationden) Float op('gas').par.Dissipationden

Default:

0.1

Range:

0 to 2

Temperature Dissipation (Dissipationtmp) Float op('gas').par.Dissipationtmp

Default:

0.25

Range:

0 to 2

Velocity Dissipation (Dissipationvel) Float op('gas').par.Dissipationvel

Default:

0

Range:

0 to 2

Turbulence / Wind (Hdrturb) Str op('gas').par.Hdrturb

Read only.

Default:

"" (Empty String)

Turbulence (curl-noise) (Turbulence) Float op('gas').par.Turbulence

Default:

0

Range:

0 to 20

Turbulence Scale (Turbulencescale) Float op('gas').par.Turbulencescale

Default:

2

Range:

0.05 to 20

Turbulence Speed (Turbulencespeed) Float op('gas').par.Turbulencespeed

Default:

1

Range:

0 to 10

Turbulence Octaves (Turbulenceoctaves) Int op('gas').par.Turbulenceoctaves

Default:

1

Range:

1 to 4

Turbulence Octave Gain (Turbulencegain) Float op('gas').par.Turbulencegain

Default:

0.5

Range:

0.05 to 1

Turbulence Lacunarity (Turbulencelacunarity) Float op('gas').par.Turbulencelacunarity

Default:

2

Range:

1.2 to 4

Turbulence Vertical Stretch (Turbulenceaniso) Float op('gas').par.Turbulenceaniso

Default:

1

Range:

0.25 to 4

Wind Direction (Windx) Float op('gas').par.Windx

Default:

0

Range:

-20 to 20

Wind Direction Y (Windy) Float op('gas').par.Windy

Default:

0

Range:

-20 to 20

Wind Direction Z (Windz) Float op('gas').par.Windz

Default:

0

Range:

-20 to 20

Wind Strength (Windstrength) Float op('gas').par.Windstrength

Default:

0

Range:

0 to 20

Force Field Strength (Plan vel:) (Fieldforce) Float op('gas').par.Fieldforce

Default:

1

Range:

0 to 20

Combustion

Combustion (Hdrcombust) Str op('gas').par.Hdrcombust

Read only.

Default:

"" (Empty String)

Combustion On (Combuston) Toggle op('gas').par.Combuston

Default:

Off

Options:

Off, On

Fuel Emit Rate (Fuelrate) Float op('gas').par.Fuelrate

Default:

4

Range:

0 to 20

Ignition Temperature (Ignitetemp) Float op('gas').par.Ignitetemp

Default:

2

Range:

0 to 40

Burn Rate (Burnrate) Float op('gas').par.Burnrate

Default:

4

Range:

0 to 40

Heat Release (Heatrelease) Float op('gas').par.Heatrelease

Default:

6

Range:

0 to 40

Soot (Smoke) Yield (Sootyield) Float op('gas').par.Sootyield

Default:

1.5

Range:

0 to 20

Fire Shaping (Hdrfireshape) Str op('gas').par.Hdrfireshape

Read only.

Default:

"" (Empty String)

Temperature Diffusion (Tempdiffuse) Float op('gas').par.Tempdiffuse

Default:

0

Range:

0 to 2

Radiative Cooling Rate (Coolingrate) Float op('gas').par.Coolingrate

Default:

0

Range:

0 to 10

Cooling Curve Exponent (Coolingexp) Float op('gas').par.Coolingexp

Default:

4

Range:

1 to 8

Cooling Reference Temp (Coolingmax) Float op('gas').par.Coolingmax

Default:

8

Range:

0.1 to 40

Emission

Box Emitter (Hdrbox) Str op('gas').par.Hdrbox

Read only.

Default:

"" (Empty String)

Emitter On (Emitteron) Toggle op('gas').par.Emitteron

Default:

On

Options:

Off, On

Emitter X (Emitterx) Float op('gas').par.Emitterx

Default:

0

Range:

-10 to 10

Emitter Y (Emittery) Float op('gas').par.Emittery

Default:

-0.7

Range:

-10 to 10

Emitter Z (Emitterz) Float op('gas').par.Emitterz

Default:

0

Range:

-10 to 10

Emitter Radius (Emitterradius) Float op('gas').par.Emitterradius

Default:

0.18

Range:

0.001 to 1

Emitter Falloff (Emitterprofile) Menu op('gas').par.Emitterprofile

Default:

0

Options:

Linear (soft), Smoothstep (round), Focused (core)

Emitter Density Rate (Emitterdensity) Float op('gas').par.Emitterdensity

Default:

3

Range:

0 to 10

Emitter Temperature Rate (Emittertemp) Float op('gas').par.Emittertemp

Default:

8

Range:

0 to 20

Emitter Look Class (Emitterlook) Menu op('gas').par.Emitterlook

Default:

0

Options:

Neutral, Smoke, Fire, Cloud, Nebula, Cel, God Ray

Emitter Velocity (jet) (Emittervelx) Float op('gas').par.Emittervelx

Default:

0

Range:

-20 to 20

Emitter Velocity (jet) Y (Emittervely) Float op('gas').par.Emittervely

Default:

0

Range:

-20 to 20

Emitter Velocity (jet) Z (Emittervelz) Float op('gas').par.Emittervelz

Default:

0

Range:

-20 to 20

Emitter Vel Pulse Amount (Emitterpulse) Float op('gas').par.Emitterpulse

Default:

0

Range:

0 to 1

Emitter Vel Pulse Freq (Hz) (Emitterpulsefreq) Float op('gas').par.Emitterpulsefreq

Default:

1

Range:

0.01 to 10

Emitter Dye Color (Emittercolorr) Float op('gas').par.Emittercolorr

Default:

0.5

Range:

0 to 1

Emitter Dye Color G (Emittercolorg) Float op('gas').par.Emittercolorg

Default:

0.5

Range:

0 to 1

Emitter Dye Color B (Emittercolorb) Float op('gas').par.Emittercolorb

Default:

0.55

Range:

0 to 1

Point Emitter (Plan points:) (Hdrpoint) Str op('gas').par.Hdrpoint

Read only.

Default:

"" (Empty String)

Points Emit Radius (Pointsradius) Float op('gas').par.Pointsradius

Default:

0.08

Range:

0.001 to 0.5

Points Density Rate (Pointsdensity) Float op('gas').par.Pointsdensity

Default:

0

Range:

0 to 10

Points Temperature Rate (Pointstemp) Float op('gas').par.Pointstemp

Default:

0

Range:

0 to 20

Points Velocity Rate (Pointsvelocity) Float op('gas').par.Pointsvelocity

Default:

0

Range:

0 to 0.2

Points Look Class (Pointslook) Menu op('gas').par.Pointslook

Default:

0

Options:

Neutral, Smoke, Fire, Cloud, Nebula, Cel, God Ray

Points Dye Color (Pointscolorr) Float op('gas').par.Pointscolorr

Default:

0.2

Range:

0 to 1

Points Dye Color G (Pointscolorg) Float op('gas').par.Pointscolorg

Default:

0.6

Range:

0 to 1

Points Dye Color B (Pointscolorb) Float op('gas').par.Pointscolorb

Default:

1

Range:

0 to 1

Look

Smoke Color (Heat Glow) (Hdrcolor) Str op('gas').par.Hdrcolor

Read only.

Default:

"" (Empty String)

Heat Tint Color (Heattintr) Float op('gas').par.Heattintr

Default:

1

Range:

0 to 1

Heat Tint Color G (Heattintg) Float op('gas').par.Heattintg

Default:

0.45

Range:

0 to 1

Heat Tint Color B (Heattintb) Float op('gas').par.Heattintb

Default:

0.12

Range:

0 to 1

Heat Ramp Temp Lo (Templo) Float op('gas').par.Templo

Default:

0

Range:

-20 to 40

Heat Ramp Temp Hi (Temphi) Float op('gas').par.Temphi

Default:

8

Range:

0.01 to 40

Color Weight (density->alpha) (Colorweight) Float op('gas').par.Colorweight

Default:

1

Range:

0 to 8