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Then, in the Liquid Simulator's Dynamics rollout, enable the Use Active Bodies parameter, and specify the Active Body Solver node.

Just as the movement of Solid

objects can be animated, the movement of

Active Bodies can also be animated as well. This way,

an Active Body can both

follow a trajectory, and

at the same time get pushed by the fluid

.

You can balance between the influence of the animation and the fluid

using the Original Animation Influence

parameter, located in the Phoenix Node Properties attributes rollout, for any Active Body.

You can also set the density and other Active Body properties in the Node Properties attributes rollout as well, for each Active Body object.

  Basic – Uses the legacy basic solver for the Active Bodies interaction. This solver does not support mutual interaction between Active Bodies, but does support Air Drag.

Interaction Steps | timestep_mult – Supported only when the Solver is set to Bullet. Determines how many calculations for the Active Bodies are performed between two consecutive fluid simulation steps - e.g. if the Steps Per Frame option of the fluid Simulator is 4 and the Interaction Steps of the Active Bodies are 10, then the rigid body simulation will do 40 steps per frame. Increasing the value will make the Active Bodies move smoother and increase the overall accuracy of the collisions at the expense of simulation time.

Fluid Density Multiplier | interaction_mult – Allows you to override the density of the simulated liquid. By default, 1.0 is considered 1000 kilograms per cubic meter (the density of water). Increasing this value will cause the Active Bodies to appear lighter and sink less inside the fluid simulation, and vice versa.

Affect by Foam | affect_by_foam – Controls how much the Foam particles will affect the Active Bodies - if set to 1.0, foam particles will push the bodies with the strength applied by the liquid particles. For example, a wave made mostly of foam would accelerate active bodies significantly. On the contrary - if this is set to 0.0, the foam would not affect the movement of the active bodies at all. Lower values of the Affect by Foam tend to work better when the simulation has a lot of foam particles, while higher values might accelerate the active bodies too much.

Collision Margin | collision_margin – Supported only when the Solver is set to Bullet. You can lower this parameter if you have groups of Active Bodies which are in contact with one another and you want to keep them still. If the value is too high, the bodies might start pushing apart for no apparent reason. On the other hand, if the Collision Margin is too low, the simulation will slow down, and also fast moving bodies might start passing through other bodies. If the latter happens and you still need the Collision Margin to be low, you can prevent bodies from passing through one another by increasing the Interaction Steps.

Air Drag | simulate_air_

drag – Applies a simple Drag force to slow down the translation and rotation of the Active Body. This option helps stabilize the motion of objects in the simulation. The Air Drag will affect the simulation only when the Basic solver is used.

Jammed Walls as Obstacles | use_jammed_walls – When enabled the Active Body Solver will use the Simulator's Jammed Walls as obstacles for the Active Bodies.

plane –  Specifies the Ground Plane geometry. The Solver expects a Phoenix FD menu → Create

→ Active Bodies Ground Plane

 object. Other object types will not work with this option.

Ground Friction | ground_

friction – Controls the amount of friction between the Ground Plane and the Active Bodies. Low

friction will allow objects to slide across the ground plane. High

friction will slow down both the objects' rotation and movement once they come into contact with the ground plane.

Ground Elasticity | ground_

elasticity – Controls the bounciness of the Active Bodies when they hit the Ground Plane. 

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