user: Describe Particles from the Blender manual or Python API, including usage steps and snippets.

assistant: # Particles

Spray
:   Create spray particles during the secondary particle simulation. Spray particles are those that
    appear to fly through the air above the liquid surface when there is a bigger splash.

Foam
:   Create foam particles during the secondary particle simulation. Foam particles are those that
    solely move on the liquid surface.

Bubbles
:   Create bubble particles during the secondary particle simulation. Bubble particles are those that
    move below the liquid surface.

Combined Export
:   Select particle types that should go into the same particle system. This option has no effect
    on the outcome of the simulation. It only changes the way particle systems are allocated in
    the particle settings.

Upres Factor
:   Factor by which to enhance the resolution of the particle simulation. The scaling factor is coupled
    to the [Resolution Divisions](../settings.html#bpy-types-fluiddomainsettings-resolution-max) (i.e. the particle
    simulation is this times bigger than the base simulation).

Wave Crest Potential Maximum
:   Upper clamping threshold for marking fluid cells as wave crests. A higher value results in less
    marked cells.

Wave Crest Potential Minimum
:   Lower clamping threshold for marking fluid cells as wave crests. A lower value results in more
    marked cells.

Trapped Air Potential Maximum
:   Upper clamping threshold for marking fluid cells where air is trapped.
    A higher value results in less marked cells.

Trapped Air Potential Minimum
:   Lower clamping threshold for marking fluid cells where air is trapped.
    A lower value results in more marked cells.

Kinetic Energy Potential Maximum
:   Upper clamping threshold that indicates the fluid speed where cells start to emit particles.
    A higher value results in generally less particles.

Kinetic Energy Potential Minimum
:   Lower clamping threshold that indicates the fluid speed where cells start to emit particles.
    A lower value results in generally more particles.

Potential Radius
:   Radius to compute potential for each cell. Higher values are slower but create smoother potential grids.

Particle Update Radius
:   Radius to compute position update for each particle.
    Higher values are slower but particles move less chaotic.

Wave Crest Particle Sampling
:   Maximum number of particles generated per wave crest cell per frame.

Trapped Air Particle Sampling
:   Maximum number of particles generated per trapped air cell per frame.

Particle Life Maximum
:   Highest possible particle lifetime.

Particle Life Minimum
:   Lowest possible particle lifetime.

Bubble Buoyancy
:   Amount of buoyancy force that rises bubbles. A high value results in bubble movement mainly upwards.

Bubble Drag
:   Amount of drag force that moves bubbles along with the fluid. A high value results in bubble movement
    mainly along with the fluid.

Particles in Boundary
:   Delete:
    :   Delete secondary particles that are inside obstacles or left the domain.

    Push Out:
    :   Push secondary particles that left the domain back into the domain.

Bake Particles, Free Particles
:   This option is only available when using the [Modular](../cache.html#bpy-types-fluiddomainsettings-cache-type) cache type.

    The progress will be displayed in the status bar. Pressing `Esc` will pause the simulation.

    Once the simulation has been baked, the cache can be deleted by pressing *Free Particles*.
    It is possible to pause or resume a *Bake Particles* process.