Method

This node is the root and container for every particle system. Particle Emitters, Particle Affectors and Particle Rendering Nodes must be parented to this node directly or indirectly in order to be operational. The node contains a number of controls that are globally effective across the system.

The Pre-Roll Time parameter is used to cause the particle update process to run for a given number of seconds before the first frame is rendered. This allows systems to be “warmed up” so particles are already emitted and moving in space before the first rendered frame, at the cost of some performance overhead – making it not recommended for real-time projects.

The simulation of particle systems has some inherent randomness and variation, in part because of random seed values used to vary behaviour over time, and in part because of operational orders of processing on the PC hardware. This means that a simulation run multiple times or on multiple PCs at once may result in slightly different positions as a result. While this is often acceptable, in some cases it is desirable for simulations to be deterministic when played by multiple servers simultaneously – for example when the same particle system is output to multiple overlapping projectors by multiple servers. The “Deterministic” parameter is used to force particle simulations to behave in a deterministic manner by locking random seeds and reordering processing so it occurs in the same order every time, at the cost of some performance overhead. In order to achieve a deterministic result it is also necessary to ensure the simulation is updated at an identical frame rate and time on every server.

In general simulations are intended to be frame rate independent. The same simulation run multiple times at differing frame rates should result in particles that are at approximately the same positions in space; the results should be visually similar. However some simulations are inherently highly dependent on update rate, e.g. where fluid solvers such as SPH are used. Where deterministic behaviour for such a system is necessary so that exactly the same results are achieved every time, the Fixed Update parameters may be used to lock or restrict the frame rate at which the system is updated. This is typically desirable for projects that are to be rendered to video.

Attributes

Name Description
Num Particles Number of particles generated in the particle system.
Pre-roll Time Pre-generate the particle system with a time delay in seconds.
Emission Update Active Controls whether any emitters in the system are allowed to emit new particles.
Physics Velocity Dampening Dampens the velocities created by physics based effectors such as Force Affector or SPH across multiple frames.
Fixed Update Rate Enabled Force the particle system to update at a constant rate.
Fixed Update Framerate The frame rate the particle system is forced to play at.
Fixed Update Mode Controls how the fixed update rate is used, if the actual frame update rate is faster than the fixed particle update rate.
  • Lock Update Delta, steps particles between fixed update frames
  • Interpolate, interpolates particles between fixed update frames.
Shading Smoothing Smooths the colours generated by Particle Shading nodes across multiple frames.
Motion Smoothing Smooths the directions of motion of particles in the system across multiple frames.
Terminal Velocity The maximum velocity allowed for particles.
Master Size Scale Scales the size of all the particles in the system.
Master Alpha Scale Scales the alpha value of all the particles in the system.
Master Brightness Scale Scales the brightness of all the particles in the system.
Deterministic Make simulations deterministic as long as other conditions are met.
Show Metrics Displays metrics, describing the particle count max, the particle count active, and the average particle count.

Inputs

Name Description Typical Node Input
Transform Modifier Links all transform properties to the input node. Null
Target Node Always faces the x-axis towards the inputs anchor point. Null
Local Transform Override Override the transformation values of the node, relative to its parent. Null

Outputs

The outputs section for this node is currently being worked on.