The Optional Channels attributes can be found in the bifrostLiquidProperties attributes.
Display Curvature and Churn as color channels to visualize the potential locations for foam emission in the liquid. If your simulation does not emit foam particles, leave these options off to avoid unnecessary computations. See Display Bifröst diagnostic information and Control Bifrost foam emission.
Enables the calculation of the Curvature channel, that is, the curved shapes on the liquid surface, such as those generated by rolling and cresting waves.
Enables the calculation of the Churn channel which refers to the rotational and angular momentum in the liquid.
Enables the calculation of the Age channel. Each particle's age is 0.0 when it is emitted, and gets incremented every time step. The Age channel can be used in conjunction with Kill fields to delete particles based on their lifespan.