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When an agent is created its DG is empty , then and it gets populated by the Behaviour Modules of its parent Agent Group.
Each Behaviour Modules At the beginning of the simulation, each Behaviour Module will either add new nodes or initialize some metadatas at the beginning of the simulation. The Behaviour modules will keep editing the graph or edit the metadatas during the simulation.
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Operators are special nodes computing a pose and passing it forward through a an output pose port. They can optionally have an pose port as input, in this way you can have a cascade of operators.
Let's have a look at the following example network. There are three operators: the clipReader, pelvisOperator and footOperator nodes. As said, they They all have an output pose port except of the clipReader.
The clipReader reads an Animation Clip object and passes the pose at the current time to the PelvisOperator which then does a bunch of other operations on the pose like placing the agent at the right height on the ground. The foot operator takes care of locking the feet on the ground.
This network was build automatically by a Behaviour Modules called "clipReader".
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