Birth Flow operator

The Birth Flow operator allows you to birth new particles that are copies of particles from another flow.

Source flow

  • Flow object: the tyFlow object whose particles will be copied.

  • Initial reference frame: the initial frame of reference that the input flow object will be evaluated at.

  • Simulation groups: controls which particle simulation groups will be read from the input flow object.

  • Channels: controls which particle data channels to copy from the input flow object’s particles.

Birth Flow cannot import bindings/cloth/PhysX data/actor-dependencies/etc from other flows. Only data from the selected channels will carry over.

Particle birth

  • Start/End: controls the time range in which to birth new particles, copied from the input flow object.

  • New particles only: controls whether only new particles will be birthed each frame. A particle is considered new if its input ID has not been processed on a previous frame.

  • Index is ID: stores the tracking ID as the particle’s system index, rather than its explicit ID. Enable this setting if the interface returns invalid particle IDs.

Birth Flow operators are useful for optimizing the initial states of flows. For example, imagine a flow that computes a voronoi fracture on 1000 particle meshes at frame 0. Every time a property of that flow is changed, the flow’s simulation will reset and the voronoi fracture will be recomputed in the process. To avoid having to wait for the fractures to initialize each time the flow property is changed, a secondary flow could be created that uses a birth flow operator in order to copy the fractured particles from the first. Each time the second flow’s properties change, the voronoi fracture of the input flow will not have to be recomputed as well. And each time the first flow’s settings change, the second flow will be automatically updated in the process. In this way, flows can be connected together in order to minimize recomputation costs of complex initial state parameters.