Simulate Burning Rigid Bodies in Blender

This guide outlines the process of combining Blender's Rigid Body dynamics with the Mantaflow fluid simulation system to create realistic, burning physical objects. By synchronizing physical collisions with fire and smoke emission, you can simulate objects like flaming debris, falling meteors, or burning timber interacting naturally with their environment.

1. Set Up the Rigid Body Simulation

  1. Select the object intended to burn and navigate to the Physics Properties tab.
  2. Click Rigid Body, set the type to Active, and adjust the weight and collision shape (use Convex Hull or Mesh for complex shapes).
  3. Create a ground plane, enable Rigid Body, and set its type to Passive so the active object can collide with it.
  4. Test the animation by pressing the spacebar to ensure the rigid body falls and collides as expected.

2. Bake the Rigid Body Physics

To prevent calculation conflicts between rigid bodies and smoke emission, bake the physics to keyframes:

  1. Select your active rigid body object.
  2. In the 3D Viewport header, navigate to Object > Rigid Body > Bake to Keyframes.
  3. Set the desired frame range and confirm. This converts the dynamic simulation into standard keyframe movement, ensuring the fluid engine precisely tracks the mesh's position.

3. Configure the Smoke and Fire Flow Object

  1. With the baked object selected, go to the Physics Properties tab and click Fluid.
  2. Set the Type to Flow.
  3. Set the Flow Type to Fire + Smoke (or Fire depending on the desired effect).
  4. Set Flow Behavior to Inflow for continuous burning, or Geometry for a brief ignition.
  5. Enable Initial Velocity to ensure the smoke inherits the speed and direction of the moving rigid body.

4. Create and Configure the Fluid Domain

  1. Add a cube to the scene that encompasses the entire trajectory of your rigid body and scale it appropriately.
  2. In the Physics Properties tab, click Fluid and set the Type to Domain.
  3. Change the Domain Type to Gas.
  4. Increase the Resolution Divisions (start with 64 for testing, 128+ for final renders).
  5. Enable Adaptive Domain to optimize render and simulation times by confining calculations to the active smoke area.
  6. Under the Fire settings, adjust Reaction Speed and Flame Smoke to balance the amount of fire versus trailing smoke.

5. Bake the Fluid Simulation

  1. In the Domain's Cache settings, set the Type to All or Modular.
  2. Define the start and end frames to match your animation.
  3. Click Bake All (or Bake Data) to calculate the smoke and fire interaction over the baked rigid body movement.

6. Shading and Rendering

  1. Select the Domain object and open the Shader Editor.
  2. Ensure the material uses a Principled Volume node connected to the Volume input of the Material Output.
  3. Increase the Blackbody Intensity to drive the fire’s brightness based on the simulation temperature, and adjust Density to control smoke thickness.
  4. Render using Cycles for accurate volumetric lighting and self-shadowing, or EEVEE with volumetric lighting enabled for faster output.