The Lock/Bond test is a versatile tool for locking particles to objects. By combining its controls in different ways, as described in this topic, you can create a variety of effects.
Lock/Bond has three main functions:
In setting up these effects, you will find that the four most important parameters are Lock To Surface, Snap To Surface, Restrict To Surface, and Force. Different settings for these parameters, along with a few other parameters and operators, can create a variety of effects with Lock/Bond.
When particles enter an event containing a Lock/Bond test with the Snap To Surface option enabled, each particle is locked to a specific point on the selected object's surface. This point is referred to as the particle's lock point. If the object is animated, the lock points animate along with the object.
With Lock/Bond, particle attachment is controlled largely by the Force % parameter in the Position Lock/Bond group. In general, when Force %=100.0, particles stay firmly stuck to their lock points, even on an animated object. For firm attachment, the Lock/Bond test should be the last action in the event. If there are other operators below Lock/Bond that modify speed, then the overall attachment might not be as firm as desired.
All parameters in the Lock/Bond test are animatable. Therefore, you can animate Force % to lock down particles gradually or loosen them from their locked positions.
The standard Position Object operator can generate particles randomly on the surface of an object. Position Object is useful for some types of animation, but is limited in its functionality. The Lock/Bond test overcomes many of these limitations, as described in the following points:
The Position Object operator can be useful in conjunction with the Lock/Bond test. For example, you can use Position Object to cover an object with particles before locking them down with Lock/Bond, as described in the following section.
To cover an object in particles, add a Position Object operator to the same event as the Lock/Bond test. The Position Object operator places particles randomly on the surface, while the Lock/Bond test locks or animates them with Lock/Bond forces and parameters.
To cover the object with particles, make sure the Amount setting in the Birth operator is high enough to create the necessary quantity of particles. The Birth Texture operator generates complete, even coverage when using Face subdivision.
After the object is covered in particles, you can lock them to the surface as the object animates, make them drift over the surface, or fling them off the object.
An animated surface is one that deforms, or changes shape, over time. Examples of animated surfaces are objects with:
Transform animation (position, rotation, scale) at the object level is not considered an animated surface.
Use these parameters to lock particles to an animated surface:
| Parameter | Value |
|---|---|
| Lock To Surface | On |
| Animated Surface | On |
| Snap To Surface | On |
| Offset Limit | Off |
| Speed Limit | Off |
| Force % | 100.0 |
When Force %=100.0, particles stay firmly stuck to their lock points. The exception is when Speed Limit is on and the object is animated. In that case, particles stick to their lock points only if they can keep up with them without exceeding the specified velocity (Speed Limit). If this parameter is off, there is no distance or speed limit, and particles stay firmly stuck to their lock points.
A Force % value of 100.0, coupled with Offset Limit and Speed Limit off, forces the particles to stay on the surface.
To allow particles to move along an object's surface, Restrict To Surface must be on and the Force % parameter in the Position Lock/Bond group must be set to a value lower than 100.0.
Any Speed or Force operators in the event will then act on the particles to move them along the surface. These forces are applied in such a way that they cause the particles to oscillate with and against the force, gradually slowing down (dampening). You can control the amount of dampening in the particles' motion with the Dampening parameters in the Position Lock/Bond group.
When Restrict To Surface is on, all Force and Speed operators should be above the Lock/Bond test, while Collision and Spawn tests should be below the Lock/Bond test.
If you want particles to drift along the surface of an object, use the following settings:
| Parameter | Value |
|---|---|
| Lock To Surface | On |
| Snap To Surface | On |
| Restrict To Surface | On |
| Force % | 50.0 (or any value lower than 100.0) |
Add Speed and Force operators to the event to make the particles move in a particular direction. For example, you can use a Wind space warp with a Force operator to push all the particles onto one end of the object.
Lock/Bond can also cause particles to drift slightly but always stay a short distance from their lock points. The area around each particle's lock point is called the central zone. Each particle has its own central zone, which extends to a specified radius around the lock point.
| Parameter | Value |
|---|---|
| Lock To Surface | On |
| Snap To Surface | On |
| Restrict To Surface | Off |
| Force % | 50.0 (or any value lower than 100.0) |
In the No Force In Central Zone group, turn on For Acceleration or For Dampening, and set Radius to the distance around each lock point in which the particle can freely move. The Radius setting determines the central zone.
Lock/Bond can also cause particles to be ejected, released, or flung from an object's surface when they achieve a specific speed or acceleration.
Use this technique when particles are glued to the object's surface and have no speed of their own, and any speed or acceleration comes from animation of the object itself. Examples include a fast-spinning or fast-moving object, or one with sub-object animation that moves one part of the object at a fast speed.
Use these parameters to cause particles to break off a fast-moving object:
| Parameter | Value |
|---|---|
| Lock To Surface | On |
| Snap To Surface | On |
| Restrict To Surface | Off |
| Force % | 100.0 |
| Break Off When Exceeds | On |
Under Break Off When Exceeds, choose either Speed or Acceleration, and set the speed or acceleration where particles should break off. Use the Acceleration method to simulate an object shaking off particles. When the object suddenly stops shaking the particles will fly off the object.
Particles that break off pass the Lock/Bond test and can be passed to another event. Use a Force operator in the next event to specify how the particles will behave after they are released from the object.
To cause particles to break off an object as they move along the surface and achieve a specific speed of their own, use the settings described in the preceding section Moving Particles Along a Surface, and use a Speed Test operator to test particle speed and break to a new event.