• FLIP container Creates a domain for a SOP FLIP fluid simulation.
    • SideFx docs
      • This node creates and initializes a SOP particle fluid domain.
      • The Particle Separation parameter controls the domain’s resolution, but also the number of particles and voxels, and the resolution of collision objects.


  • FLIP boundary
    Creates a surface or density VDB for sourcing or deleting SOP FLIP fluid particles.
    • SideFx docs
      • The FLIP Boundary SOP converts its input geometry into a volume that can be used to control simulations. It’s also possible to directly connect a volume. You can also combine multiple objects through a Merge SOP to get more complex shapes.
      • The FLIP Boundary node provides two modes: Source and Sink


  • FLIP solver
    Evolves an object as a FLIP fluid object inside a SOP network.
    • SideFx docs
      • A FLIP solver is a type of hybrid between a particle based and volume based fluid simulations. All fluid data is stored in the particles and only particles need to persist frame to frame, ensuring no unwanted mixing or loss of fluid can occur. However, the pressure projection step is done on a volume that is created just in time.
      • The fluid is represented by particles with their pscale, and can be moved around with POP and DOP forces.
    • Parameters
      • Setup >
        • General >
          • Time Scale
        • Simulation >
          • Sub Steps
          • Cache Memory
      • Fluid Behaviour >
        • Velocity Transfer
          • APIC Swirly (Better for smaller sims)
        • Air Incompressibility
          • The divergence free constraint will now also be applied to the air volume. This will prevent air volumes from collapsing and create rising bubbles. This is useful for capturing realistic air-liquid interaction like a glugging watercooler.
          • Note
            • This does not work with Pressure Adaptivity.
        • Enforce Pareticle Separtion
          • Despite the velocity projection stage, particles can end up closer together than their pscale attribute. When this happens, internal forces can’t separate the particles because the velocity projection will remove those forces. This results in the fluid compressing over time.
        • Reseeding
          • Create new particles in voxels where the particle count has dropped too low to properly represent the fluid surface, and delete particles in voxels that have become too crowded. Reseeding can help avoid collapsing pockets of air forming in the fluid near collisions, as well as provide a smoother surface from which to generate a polygonal mesh.
          • Note
            • If you want to turn of reseeding (Fluid Behaviour) you first need to disable Advanced > Solving > Enable Particle Narrow Band
          • ID
            • If reseeding is disabled we can better make use of the particle id since particles will not be added/removed.