Advection-Reflection attempts to inject energy lost due to pressure projection back into the simulation. Enabling this option may exhibit better vortex retainment in the flow.

Fraction of the projected velocities to re-inject when Advection-Reflection is not set to Disabled. Values near 1 will do a better job of conserving energy, but may result in instabilities.

The following video shows Single-Project mode.

The following video shows Double-Project mode.

A blur factor on the temperature field. Higher values diffuse the temperature out further, emulating the spread of heat from hotter to colder areas.

How fast the temperature field cools to zero.

Temperature corresponding to value of 0 in the temperature field (in Kelvin). This represents the ambient temperature of the environment.

Temperature corresponding to value of 1 in the temperature field (in Kelvin). The temperature range is used to calculate strength of the buoyancy force.

Hot gas expands, causing it to rise due to lowered density. Acceleration due to buoyancy is calculated using values of the ambient and reference temperatures, as well as the Gravity settings. Value of this parameter is used as a multiplier for the buoyancy force.

When enabled, density is added to the simulation in the specified Flame Range.

Amount of density output from the flame field. This parameter acts as a multiplier for the remapped flame value.

Controls how the output of the flame field is mixed with the density field.

The range of values in the flame field that will generate an output. The flame field is first fitted from this range to 0-1; if Remap Flame is enabled, the Flame Ramp is then evaluated at this value. The final output is the product of this remapped flame value and Emission Amount.

When enabled, Flame Ramp is evaluated at the refitted flame value (from Flame Range to 0-1) to generate the output.

Ramp that controls outputs at different flame field values.

When enabled, temperature is added to the simulation in the specified Flame Range.

Amount of temperature output from the flame field. This parameter acts as a multiplier for the remapped flame value.

Controls how the output of the flame field is mixed with the temperature field.

How strongly the temperature field values are pushed towards the hotter flame output when Merge Method is set to Pull.

The range of values in the flame field that will generate an output. The flame field is first fitted from this range to 0-1; if Remap Flame is enabled, the Flame Ramp is then evaluated at this value. The final output is the product of this remapped flame value and Temperature Amount.

When enabled, Flame Ramp is evaluated at the refitted flame value (from Flame Range to 0-1) to generate the output.

Ramp that controls outputs at different flame field values.

When enabled, goal divergence is added to the simulation in the specified Flame Range, causing expansion.

Amount of divergence from the flame field. Larger values result in a more violent expansion. Negative values cause the gas to be sucked inwards (instead of blown outwards).

The range of values in the flame field that will generate an output. The flame field is first fitted from this range to 0-1; if Remap Flame is enabled, the Flame Ramp is then evaluated at this value. The final output is the product of this remapped flame value and Expansion Rate.

When enabled, Flame Ramp is evaluated at the refitted flame value (from Flame Range to 0-1) to generate the output.

Ramp that controls outputs at different flame field values.

When this option is turned on, density values that fall below the provided threshold are driven all the way down to 0. It is recommended to leave this enabled for sparse simulations, for otherwise tiny density values will keep the active region unnecessarily large.

Disturbance is meant to mimic random motion in the air surrounding the smoke. To this end, it is applied only where the value of the Threshold Field falls below Cutoff.

Disturbance is applied only where value of the Threshold Field falls below this Cutoff.

Controls the nature of the generated random vectors.

Variance of the aggregated force over a region of this size will be equal to Disturbance amount when Mode is set to Continuous. Provides a scale for normalizing the force against voxel size. A larger value for this parameter will increase magnitude of the applied force.

Controls size of the biggest blocks in the generated noise pattern when Mode is set to Block-Based.

Length of time (in seconds) that the noise pattern is held fixed; only applies when Mode is set to Block-Based.

The ratio of block sizes between successive noise layers. Value of 2, for example, means that the first layer has blocks that are twice the size of the second layer; the second layer will in turn have blocks that are twice as large as the next layer. This parameter is only applicable in Block-Based mode.

The ratio of amplitudes between successive noise layers. Value of 0.5, for instance, means that the second layer will have half the amplitude of the first one. This parameter is only applicable in Block-Based mode.

The maximum number of noise levels to compose in Block-Based mode.

Shredding is meant to add chaotic motion inside the fire. To this end, value of the Shredding Field (flame by default) is fitted from the Field Range to 0-1 to act as a multiplier on top of the global Shredding amount.

Shredding Field value is fitted from this range to 0-1 to act as a multiplier on top of the global Shredding amount.

Controls size of the biggest blocks in the generated noise pattern when Mode is set to Block-Based.

Length of time (in seconds) that the noise pattern is held fixed; only applies when Mode is set to Block-Based.

The ratio of block sizes between successive noise layers. Value of 2, for example, means that the first layer has blocks that are twice the size of the second layer; the second layer will in turn have blocks that are twice as large as the next layer. This parameter is only applicable in Block-Based mode.

The ratio of amplitudes between successive noise layers. Value of 0.5, for instance, means that the second layer will have half the amplitude of the first one. This parameter is only applicable in Block-Based mode.

The maximum number of noise levels to compose in Block-Based mode.

Base swirl size in world units. Lower values produce smaller, more localized vortices, while larger values give rise to coherent long-range forces.

Controls the ratio of amplitudes between successive noise bands. Higher values increase the prevalence of higher-frequency vortices (smaller than the base Swirl Size).

Governs how fast the noise evolves. Higher values of this parameter result in slower evolution.

Acts as an offset into the noise field. Change this value to modify the resultant forces.

Number of turbulence levels to apply. Each successive layer has half the swirl size, and amplitude of the previous layer scaled by Grain.

This field determines which areas are affected by turbulence. In particular, turbulence is applied wherever value of this field exceeds Influence Threshold.

Turbulence is applied wherever value of the Influence Field exceeds this threshold.

Which direction the wind is blowing in. The actual wind velocity is the product of Wind Direction and Wind strength.

When this option is enabled, only the Alpha values are affected by dissipation: this makes it easier to color “older” smoke through sourcing. Disabling this parameter will cause dissipation to also drive Cd values toward the smoke’s default color. That is, when Only Dissipate Alpha is turned off, the smoke will gradually change its color back to the default value.

When enabled, the force exerted is scaled by the content of this field.

Map from this range of values in the control field.

Enables or disables the control field ramp.

The ramp’s vertical axis is strength of the effect and the horizontal axis is the value in the control field.

Controls how far out the colors will blur per second.

Shape of the blur kernel.

Sharpening boosts the deviation of colors from averaged (blurred) values. This parameter controls the distance to which blurring is performed.

Sharpening boosts the deviation of colors from averaged (blurred) values. If the deviation falls below this threshold at a voxel, no sharpening is done to it. Increasing this value can help reduce the amount of introduced sharpening noise.

When enabled, size changes to the fields will be done in increments of 16 voxels. This is marginally more efficient, but the resultant fields will be larger than necessary.

List of fields that determine size of the simulation container. Resizing is done by first computing the bounding box around all voxels of Reference Fields that have a positive value, then expanding this intermediate region by Padding on all sides. This list of fields is also used to build the active region in sparse mode.

Amount of padding to add to the simulation region around the Reference Fields. Padding should be as small as possible, but large enough to ensure that moving smoke does not leave the container within a timestep.

By default, the smoke solver will resize density, temperature, divergence, active, vel, collisionvel, and flame (for pyro only). Additional fields may be resized by specifying them here.

Puts the solver in sparse mode, allowing it to perform its computations only in relevant areas.

Rule that determines where the fields specified in Fields to Reset are modified.

List of fields to reset, based on the Reset Rule. In the regions where they are modified, these fields are set to their initial value.

When this parameter is enabled, newly-activated areas inherit their velocities from nearby active regions. This can help reduce tile artifacts that may appear on the smoke surface if the Padding is not large enough.

Falloff and Blendwidth parameters determine how new velocities are blended with the background field value (as set by Wind Tunnel Direction on the Smoke Object (Sparse) node). You should set Blendwidth to reflect the interpolation band around the active region: valid boundary velocities will be blended with the background value in a band of this thickness. If the Blendwidth is set too small, then extrapolation will not be effective at removing tile artifacts; however, if this value is set too large, then smoke will be accelerated outwards. If this happens, decreasing the Blendwidth or increasing Falloff (to a value on the order of simulation speeds) can help mitigate the problem.

When Extrapolate Velocity into New Tiles is enabled, valid velocity values are extrapolated into newly-activated nearby tiles. This parameter sets a minimum blending rate towards the background field value (as set by the Wind Tunnel Direction on the Smoke Object (Sparse) node). Increase this parameter if the smoke gets pulled outwards at the desired Blendwidth.

Controls the size of the interpolation band around the active region when Extrapolate Velocity into New Active Tiles is enabled. Newly-activated velocities in a band of this size will interpolate valid values towards the background value (as set by Wind Tunnel Direction). Increasing this parameter can help reduce tile artifacts that can appear when Padding is small.

When enabled, the active simulation region will take the motion of the gas into account. This will result in adaptive padding that is larger where the fluid is exiting at a faster rate. If this is disabled, the active region is expanded uniformly in all directions.

The minimum padding around the smoke when Expand by Velocity is turned on.

The maximum padding around the smoke when Expand by Velocity is turned on. You can enable this to limit the amount of internal expansion when using Expand by Velocity.

Controls size of the adaptive padding for the sparse active region, when Expand by Velocity is enabled. The active region will include more tiles (and the smoke will have a bugger buffer to move into) when this parameter is set to a larger value.

This parameter impacts the shape of the sparse active region when using Expand by Velocity. Smaller values of this parameter will permit sharper kinks in the active region. This can reduce the number of active simulation tiles, but may also negatively impact the motion of the fluid.

A list of forces to scale by the value of the density field at each voxel.

A list of forces to apply uniformly to all voxels (ignoring their density value).

If this option is enabled, the solver will build the collision and collisionvel fields, allowing automatic interaction between smoke and collision objects.

Controls how far from the collision objects the relevant fields are to be built. This value is measured in voxels. If disabled, the fields will be initialized everywhere.

The local velocity of an affector object is a combination of the angular and linear velocity. However, if the object is deforming and points match frame to frame, the local point velocity can be used as well to estimate the deformation effect.

If an affector object doesn’t have a stable point count, but does have a volume representation, the change in the volume representation can be used as an estimate of deformation velocity.

Normally, the collision relationship uses the signed distance field for each object. However, if the object is a different type you can use other ways of getting its effective signed distance field. If this option is enabled, the object is examined for a surface scalarfield, which is treated as a signed distance field. If a density field is present, it is treated as a fog volume with a 0.5 cutoff. If a Geometry geometry is attached, and it consists of a single volume, that volume will be treated as a fog volume (with cutoff of 0.5). However, if its boundary condition is set to SDF, it will be treated as an SDF.

When enabled, the specified fields will be reset inside the colliders.

These fields will be reset inside the colliders when Correct Collisions is turned on.

The degree to which the colliders are affected by smoke is controlled by the value of this parameter. Higher values will increase the effect of pressure forces on the colliders. A value of 0 will prevent any feedback.

Colliders are integrated into the system using a weak coupling approach. The number of projection iterations is controlled by this parameter. Larger values will slow down the simulation, but yield better interaction with collision objects.

Enables filtering of spurious divergent modes that may survive pressure projection when Velocity Sampling on the smoke object is set to Center.

Strength of hourglass filtering. Value of 0 disables the filtering altogether, while 1 performs full filtering.

Instead of performing the filtering everywhere, it can be selectively applied to voxels where divergence is still detected by turning this option on.

Similar to Scale by Divergence, this setting applies the filtering with different strength in different places. Instead of pure divergence, however, the quantity used to control filtering strength is the ratio of divergence to speed.

Controls how sensitive filter strength is to the remaining divergence (or divergence relative to speed if Use Relative Divergence is enabled). That is, the relevant quantity is multiplied by this amount before it is used to determine filter strength.

When using an adaptive filter (Scale by Divergence turned on), the strength field can be visualized by enabling this option.

Orientation of the cutting plane for visualization.

Relative position of the cutting plane inside the bounding box.

Determines how strength values (which fall between 0 and 1) are converted to colors.