The Birth Fluid operator can be used to birth particles inside of a (Phoenix FD) fluid grid based on grid voxel and particle properties.
Fluid object: the input fluid grid object.
Start/End: controls the time range in which to birth new particles.
Temperature: when enabled, grid cells with a temperature value above 300 will be able to spawn particles.
Smoke: when enabled, grid cells with a smoke value above 0 will be able to spawn particles.
The higher the temperature/smoke value per cell, the higher the probability that a particle will be spawned in the cell.
PhoenixFD grids can contain both voxels and particles. To birth particles that will be copies of PhoenixFD grid particles, enable the relevant particle channels.
Channels: enabling these channels will birth copies of particles contained within them, if such particles are available in the cache of the input object.
Channel percentages: controls the percentage of copied input particles to birth.
New only: controls whether only new particles will be birthed each frame. A particle is considered new if its input ID has not been processed on a previous frame.