Targets expose a number of attributes that can be adjusted to modify the way in which they affect a simulation. The attributes which are exposed will change depending on the target’s type and steering behaviour. The attributes for a target can be seen in the top section of a target rollout.
All attributes can be animated or expression driven to create more interesting flocking simulations.
Common Target Attributes
A target’s steering type defines the Steering Behaviour that it will apply to particles in the system. Certain steering types expose different attributes to the user. You can find more information about these attributes by selecting each steering type below:
The weight of a target is a scale factor which determines how much influence it should have on the overall system. The value ranges from 0 to 1, with 1 meaning that the target has full influence in the system and 0 meaning it has none.
The weight can be used in a number of situations such as to enable/disable a specific target, or to blend between different targets when there are multiple targets in the scene.
Seek targets expose the following attributes:
This attribute becomes available when using seek steering behaviour.
A seek target can operate in 1 of 2 modes, Seek or Arrival. The mode is decided by the value of the Arrival Distance attribute. If the attribute is left at 0, standard seek behaviour will be used. If the value is set to anything else, then arrival behaviour will be implemented as soon as particles get within the range of the target specified by the Arrival Distance attribute.
This value is specified in Maya’s current UI units, meaning that the value will vary depending on the units Maya is currently working in (i.e. centimeters, meters etc.)
The Flee steering type doesn’t expose any specific attributes.
Wander targets expose the following attributes:
Point attraction is an additional attractive force which pulls particles towards the wander target’s location. We recommend that you use small values to achieve the best results.
Due to the way Wander behaviour works, flocks can often be seen splitting up into small groups and flying away in different directions and not staying in one central location. The point attraction attribute is provided as a means of ensuring particles do not travel too far from the wander target itself by essentially adding a seek target to the wander target and controlling its weight.
The value ranges from 0 to 1, with a value of 0 meaning no point attraction will be applied and a value of 1 will be full point attraction.
The wander mode attribute controls what type of wandering behaviour this target should apply. The wander modes available are:
Particles will randomly change direction each frame. This can look quite twitchy but sometimes gives nice results. It is also the cheapest solution in terms of performance.
This type of wandering attempts to ensure that particles will not be able to make extreme direction changes from frame to frame. At each simulation step, a virtual sphere is projected slightly in front of the particle and the new random direction is constrained so that it must lie somewhere on the surface of that sphere.
Direction changes are set by a procedural Perlin noise function.
The wander strength attribute acts as a scale factor on how much force a particle can apply to change direction when wandering.
The value ranges from 0 to 1 with a value of 0 meaning no wandering force and a value of 1 meaning that particles can use their maximum force to change direction.
Wander Rate (Spherical Constraint Mode)
When using the spherical constraint wander mode, this attribute become available.
The wander rate attribute controls how quickly a particle can change direction when wandering. In actual fact this value scales the virtual sphere projected in front of the particle. The larger the value the larger range of motion that the particle is allowed and so therefore the more it is allowed to turn.
Path Follow Attributes
Path follow targets expose the following attributes:
Limit to Curve Direction
By default particles can follow a path in either direction. By enabling this attribute particles will be restricted to only following the path in the direction of the curve.
In Maya the direction of the curve can be seen by using the Curves > Edit Curve Tool option.
This attribute can only be used if Limit to Curve Direction is enabled.
As the name suggests, enabling this attribute will simply restrict particles to travel in the reverse curve direction.
Use Curve Volume
Enabling this attribute will activate the volume of the curve target.
When using the volume, only particles which are within the curve’s volume will be affected by it. Particles outside of the volume will not receive any influence from the target.