How to choose between liquid simulation types

Overview

Houdini has a few different ways of simulating liquid:

Particle fluid – Simulates the physical motion of many particles, then wraps the particles in a surface.
Sign distance field – Simulates movement between points in an enclosed box.
Ripple solver – Simulates the propagation of waves through a surface.

Each of these different methods has unique properties that make them more or less suited to simulate different types of fluids.

Are not constrained to the inside of a box. Can move freely anywhere in the scene.
Can separate, be concave, splatter.
More prone to spray than sign distance field.
Surfacing between particles leads to “lumpy porridge” look unless you use a huge number of particles.
Stray individual particles do not surface well. You’ll probably want to suppress stray particles.
Particles need to “settle” into shape from their initial placement. You’ll probably want to pre-roll the simulation to allow settling.

Simulates waves changing the height of a surface.
Waves can rebound against edges. You can paint attributes to create areas of fast, slow, or no wave propagation.
Waves cannot be concave – only displaces “height” of points on the surface.
Useful for simulating ocean surface.