This page provides information on the Fuel rollout for a FireSmokeSim object.


There is no need to use fuel for simple fire, which can be produced with hot air using the default settings of the Fire Source.

In case you want to use the Fuel Channel in the Volumetric Settings or the Phoenix Grid Texture, be sure to enable the export of the Fuel Grid Channel from the Output rollout of the Simulator.

The Fuel rollout controls the simulation of burning. It can be useful for gasoline explosions, or propagating fire, or other special effects that require more control over burning.

The process of burning depends on two 'regular' voxel channels (Fuel, Smoke) and a third, imaginary channel (Oxygen).

  • Oxygen is calculated as the remaining volume which is not occupied by Fuel and Smoke for a given cell / voxel. For example, if in a certain voxel you have 0.4 Fuel and 0.4 Smoke, the Oxygen would be 0.2 (for a total volume of 1 for the voxel). Burning occurs only in voxels which have both Fuel and Oxygen. If a voxel has no Fuel, or is already full of Smoke and Fuel, it won't burn at all.
  • Fuel is ignited if the Temperature in a given voxel is above the Ignition Temp. parameter.
  • When the Fuel burns, it releases more Temperature based on the Energy parameter.
  • When the Fuel burns, it releases Smoke based on the Smoke Amount parameter.
  • When the Fuel burns, it adds expanding pressure to the simulation based on the Propagation parameter. It can be animated to create explosive effects.

The burning strength is determined by the smaller of the values of the Fuel and Oxygen channels:

  • If there is 0.1 Fuel, 0.1 Smoke and 0.8 Oxygen in a voxel, the strength would be 0.1 -  the burning will be weak as there is not enough Fuel to ignite strongly. 
  • If there is 0.8 Fuel, 0.1 Smoke and 0.1 Oxygen in a voxel, burning will be weak again because the voxel is overflown with Fuel - there is not enough Oxygen to help the burning.

UI Path: ||Select Fire Smoke Simulator|| > Modify panel > Fuel rollout


Expand – Opens a floating dialog that contains the selected rollout and automatically folds the command panel rollout.

Re-Center – Resets the position of the floating rollout.

? – Opens up the help documents for the Fire/Smoke Fuel.

Enable Burningburning – Enables the simulation of burning.

Ignition Temp. | fl_ignition – The minimum temperature needed for the fuel to start burning. Keep in mind that the environment temperature is 300 Kelvins so setting this parameter to a lower value will cause the entire Fuel channel to spontaneously ignite. You can find out more about Phoenix Grid Channel Ranges here.

Energy | fl_energy – Controls how much temperature is produced by the burning fuel and how strong the expanding pressure is. A very high value will produce a rapidly increasing in size balloon of flames. Ideally, you would like just the right amount of Energy to release enough Temperature to ignite the neighboring fuel.

Fuel Depletion | fl_fueldepletion – The rate at which the Fuel channel burns out. You can use this parameter in conjunction with the Fuel Buoyancy on the Dynamics rollout to produce lingering flames that travel upwards with the Smoke.

Smoke Amount | fl_smokeamount – Multiplier for the amount of Smoke produced during burning. Note that if too much smoke is produced, the burning will decrease as no Oxygen would remain to sustain burning, even if there is enough Fuel.

Smoke Threshold | fl_smokethres – When the Oxygen in a voxel is less than the Fuel, this value controls how much of the burning Fuel produces Smoke. Higher values cause less of the burning fuel to produce Smoke.

Burn Smoke RGB | burn_smoke_rgb_on, burn_smoke_rgb – Specifies the RGB color for the smoke created by burning fuel.

Propagation | fl_propg – Controls the speed of expansion of the fire and smoke generated by the burning fuel. If your simulation is exploding in a big bubble, consider reducing the Propagation or the Energy.


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