Initialize and Freeze All Particles
Add the script to Simulation Flow (Ctrl/Cmd + F2) > SimulationPre.
The script freezes a particle volume at the beginning of the simulation (works with standard particle fluids only):
emitter = scene.get_PB_Emitter("Circle01")
particles = emitter.getParticles()
for particle in particles:
particle.freeze()
Unfreeze Particles
Add the script to Simulation Flow (Ctrl/Cmd + F2) > FramesPre or StepsPre.
The script unfreezes a particle (only works with standard particle fluids) when an animated object (here: "Sphere01") is 0.75 m or less away from the particle:
emitter = scene.get_PB_Emitter("Circle01")
particles = emitter.getParticles()
unfreezeObject = scene.getObject("Sphere01")
for particle in particles:
particlePosition = particle.getPosition()
objectPosition = unfreezeObject.getParameter("Position")
particleObjectDistance = particlePosition.distance(objectPosition)
if (particleObjectDistance <= 0.75): particle.unfreeze()