Work with Bifröst Aero

Aero simulations can be used to create effects like smoke, mist, and other gases.

Get started with aero

Here is a quick overview of the main steps for creating an aero simulation.

1. Select one or more polygon mesh objects that you want to act as emitters.

   The selected meshes will all use the same emitter properties (Continuous Emission on or off, Temperature, and so on), but you can add other emitters later. See Work with Bifröst emitters.

2. Select Bifrost > Create Aero.
3. In the main aero properties, you might need to adjust Gravity Magnitude and Air Density if the scene was not modeled to a scale of 1 centimeter = 1 meter. See Bifröst simulations and scene scale.
4. Play back a few frames and adjust Master Voxel Size if necessary. You should use a value that's small enough to give a good sense of the overall effect in relation to the size of other objects in the scene, but still high enough for fast, low-resolution previews.

   Note that the simulation updates with new settings only after you return to the first frame (by default, frame 1).

5. Make sure that the emitter properties are set as desired. For example, turn off Continuous Emission if you just want a single puff of smoke, and adjust Density and Temperature to match the substance you want to simulate. The default values work well for generic smoke.

   If desired, you can paint Density and Temperature to have them vary across an emitter's surface. See Paint Bifrost attributes.

6. Add any other objects that you want to use to control the simulation. For example:
   • Add colliders to make the aero flow around solid objects.
   • Add motion fields to simulate forces like wind and drag.
   • Add killplanes or kill fields to reduce memory and computation if particles move outside of the camera's view.
7. Play the scene to preview the whole simulation. See Preview a Bifröst simulation.
8. Adjust attributes and preview again until you are satisfied with the overall motion at low resolution. In particular, some attributes in the main aero properties that you might want to tweak include:
   • Smoke Threshold and Smoke DIssipation to control how the effect fades off.
   • Randomize Velocity to break up large, smooth flows and add visual detail.
9. When satisfied with the overall motion, you can increase Master Voxel Size for more detail in the FLIP simulation, or Voxel Size Render Factor for more detail only in the render (see Bifrost Resolution attributes. You can also adjust the Particle Density for the FLIP and Render particles.

   For a smoother result, especially when particles spread out over a large volume, you can activate Reduce Flow Noise in the Particle Density Attribute group of the main aero properties.

10. When done, you can render the result. This depends on the renderer that you are using, so consult the documentation for your renderer. If desired, you can also:
    • Create a user cache, for example, to render on a farm or import into another scene. See Work with Bifröst user caches.
    • Mesh the aero surface. See Work with Bifröst meshes.