How to Assign Flame and Smoke Fuel in Blender

Creating fire and smoke simulations in Blender requires configuring a physics domain alongside an emitter known as a flow object. By assigning the correct flow behavior and adjusting the fuel property, you can control the rate, intensity, and duration of combustion in your scene. This guide walks you through the exact steps to enable Mantaflow physics, set your flow object to generate fire and smoke, and fine-tune its fuel settings.

1. Create the Domain and Flow Objects

  1. Open Blender and add two mesh objects to your 3D Viewport: a larger cube to serve as the simulation boundary (Domain) and a smaller mesh inside it to act as the emitter (Flow object).
  2. Select the larger cube, navigate to the Physics Properties tab (the blue atom icon), and click Fluid.
  3. Set the Type to Domain, and change the Domain Type to Gas.

2. Configure the Flow Object

  1. Select the smaller emitter object inside the domain.
  2. Go to the Physics Properties tab and click Fluid.
  3. Set the Type to Flow.
  4. Change the Flow Type to Fire + Smoke (or Fire if you only want combustion without dense smoke).
  5. Set the Flow Behavior according to your needs:
    • Inflow: Continuously generates fire and smoke based on the fuel amount.
    • Geometry: Emits a single burst using the object's initial volume.
    • Outflow: Removes fluid from the simulation.

3. Adjust the Fuel Parameter

  1. Under the Flow Settings panel on the flow object, locate the Fuel slider.
  2. The Fuel value determines the amount of burnable material injected into the simulation:
    • A value of 1.0 represents standard combustion.
    • Increasing the value above 1.0 creates larger, more explosive, and longer-lasting flames.
    • Lowering the value below 1.0 results in smaller, faster-burning flames that quickly turn into smoke.

4. Optional: Control Fuel with Vertex Groups or Textures

  1. To vary fuel emission across the surface of your object, go to the Flow Settings section.
  2. Scroll down to the Vertex Group field and select a predefined vertex group from your mesh to restrict fuel emission to specific vertices.
  3. Alternatively, check the Texture box under Flow Settings to use a procedural or image texture to drive where fuel is generated across the mesh.

5. Run the Simulation

Select the Domain object, scroll down to the Cache section in the Physics Properties, set the cache type to Modular or All, and press the Play button (Spacebar) on your timeline or click Bake Data to view the fire and smoke reaction.