Currently, Houdini only supports one-way interaction from agents to other solvers. For example, an agent can knock over an RBD object or splash through water, but an RBD object can’t knock over an agent.

• On the Agent ROP or Agent SOP that was used to create the agents, ensure that the Generate Collision Layer parameter is enabled. This will create a layer that contains a low-res static shape for each bone in the rig, which can be used for efficient collision detection.

• Use a Delete SOP to remove distant agents that will not collide with any objects in the simulation.

1. Use the Agent Edit SOP to switch the agents' current layers to their collision layer, and use an Unpack SOP to unpack the agents.

2. Use the RBD Fractured Object shelf tool to create RBD objects for the shapes from the agents' collision layers.

3. On the newly-created RBD Packed Object DOP, set the Initial Object Type parameter to Create Animated Static Objects. This will cause the RBD objects' transforms to be updated each frame to match the motion of the agents.

• Consider changing the Geometry Representation parameter to a primitive shape (such as Capsule or Box), which can improve performance.

1. Use the Unpack SOP to unpack the agents.

2. Use the Deforming Object shelf tool to bring the collision geometry into the fluid or particle simulation.

• If you want to create secondary simulation (for example, simulated clothing) on top of agent geometry, currently you must unpack the agent geometry.

• You can use VEX or Python functions to calculate the positions of agent body parts (for example, if you want to generate particles flowing from the top of agent heads) from the agent attributes. You can see an example of this in this example scene file:

  $HH/Help/files/joint_positions.hip.