xpSpin

xpSpin spins or rotates the particles.

Object Properties

Enabled

Checking this box activates xpSpin.

Mode

Set at Independent, by default.

You can change this to Action-Controlled.

Independent Mode

In this mode, particles will be affected if they come into the field of effect of the modifier.

Action-Controlled Mode

When in the Action-Controlled Mode setting, the modifier will only act on a particle when told to do so by an action.

Operation

Set as Spin, by default.

The alternative is Rotate.

Spin

The modifier spins the particles.

That is, if xpSpin is present, then the particles spin using values from the modifier rather than the emitter, even if the modifier spin values are zero (no spin).

Rotate

The modifier will rotate particles to a specific rotation, but does not spin them continuously.

Different parameter options are available in this mode.

Spin operation settings

You do this by enabling Use Rotation in the xpEmitter Extended Data tab.

This sets up a data structure that all particle rotations require.

This data structure is not set up by default in order to save memory.

Spin Time

Set as Per Frame, by default.

The alternative setting is Per Second.

Per Frame

The values given in Spin Amount and other parameters are considered to be the value to spin the particle each frame.

In other words, if Spin Amount is set to 5 degrees on each axis, the particle will spin by 5 degrees each frame.

Per Second

In this case, the values given in Spin Amount and other parameters are considered to be the value to spin the particle each second.

In other words, if Spin Amount is set to 60 degrees on each axis, and the frame rate is 30 frames per second, the particle will spin by 2 degrees (60/30 = 2) each frame.

Spin Amount

This is the change to apply to the rotation of the object whose associated particle passes into the modifier’s field of effect.

These values represent the change in rotation each frame so, in general, should be kept quite small; 10 degrees per frame is quite fast.

Negative values can be entered to spin the objects in the opposite direction.

When used with fields, the full amount of spin is applied to particles passing through the modifier’s inner offset zone; those in the field of effect have their spin altered in a reduced amount, depending on the strength of the falloff.

This animation, with Operation set to Spin, illustrates a Spin Amount in the bank, keyframed to 0.5.

Increment Spin

This parameter and the Increment Value parameter can be used to increase the amount of spin as the particle passes through the modifier, making it spin faster and faster (or slower, if the increment is a negative value).

Enable this parameter to gain access to the increment value field and to increase the spin each frame.

Increment Value

If Increment Spin is enabled, the particle spin will increase by the value in this field each frame.

You can use this to speed up or slow down a particle spin.

The values you can enter are limited to 45 degrees, as values higher than this can give rise to incorrect results, such as the particle appearing to spin slowly backwards instead of very fast forwards.

If you use a negative value in this setting, the particle spin will slow down but it will eventually reverse and spin the particle in the opposite direction.

If the value is too high, the change in spin will appear to be instantaneous.

In this scene, with a very similar set up, Increment Spin is enabled, with an Increment Value of 0.1 in the heading.

Clamp Spin, Clamp To

If Clamp Spin is enabled, the amount of spin is limited to the value in Clamp To.

Animation, with Clamp Spin enabled and the heading clamped to 10 degrees. Because the pitch and bank are set at 0 (zero) degrees, the Spin Amount value no longer works.

The settings are the same here, except now the bank also has a Clamp To setting of 45 degrees, allowing the Spin Amount setting to continue as before.

Randomize Spin, Random Spin Value

To give a particle a random spin, enable this setting.

The particle will then spin in either direction by a random value.

The scene in this animation is the same as above, but with Randomize Spin enabled and a Random Spin Value of 2 degrees on the heading.

Unidirectional

This option is only available if Randomize Spin is enabled.

By default, the object may spin in either direction, so some spin forwards and others backwards.

If you only want the random spin to take place in one direction, enable this parameter.

The spin can be reversed by using a negative value in Random Spin Value.

Rotate operation settings

User Interface (UI) with Operation set to Rotate.

Unlike Spin mode, this will work whether or not that option is enabled.

Rotation Mode

Set as Absolute, by default.

The alternatives are: Relative, Face Camera, Face Object, Face Screen and Tangential.

Absolute

The particles will be rotated to the value in the Rotation field.

With Operation set to Rotate, in this animation, the Rotation Mode is set to Absolute, with Rotation keyframed to 120 degrees on the heading.

Relative

The particles will be rotated to a value which is their current rotation plus the value from the Rotation field.

Animation to demonstrate the Rotation Mode of Relative, with Rotation again keyframed to 120 degrees on the heading.

Face Camera

The particles will be rotated so their Z axis points to the current scene camera.

As they move, the rotation will be updated so they always point at the camera.

Here, the Rotation Mode is Face Camera, with a Spherical field showing the effect over time.

Face Object

The particles will be rotated so their Z axis points to the object specified in the Object field, if there is one.

As they move, the rotation will be updated so they always point at the object.

In this scene, the Rotation Mode is set to Face Object, that object being the Cube, dropped into the Object field.

Face Screen

The particles are rotated so that they always face the screen.

This is not the same as Face Camera since the particles will always appear face-on to the screen regardless of camera movement or rotation.

In this animation, the Rotation Mode is Face Screen, with the particles continually rotating to face the screen.

Tangential

This option does the same thing as the Tangential setting in the emitter’s Extended Data tab; the particle is rotated to point along its direction of movement.

Being in a modifier gives more control over when tangential rotation is used.

You can also choose the axis along which to point in the Tangential Axis parameter.

Object

The object to point at, in Face Object mode.

Use Time

This is only available in Absolute or Relative modes.

If enabled, the change in rotation will take place over the time given in the Time field.

In this scene, with Rotation Mode set to Always, Use Time is enabled, with a Time of 90 frames directing the duration for the change in rotation.

Time

This is only available in Absolute or Relative modes and when Use Time is enabled.

It gives the amount of time taken to change the rotation.

A value of zero will cause the change to take place immediately (just as if Use Time was disabled).

Tangential Axis

This parameter is only available if Rotation Mode is set to Tangential.

By default, with tangential rotation the Z axis of the particle points along the direction of movement.

If you use the emitter to set tangential rotation, the Z axis is used by default - although the X or Y axis can be used instead.

With this parameter, you can choose which axis to point along the movement of the particle.

The options are either X, Y or Z, with Z as the default axis.

Rotation Offset

This parameter is only available if Rotation Mode is set to Tangential.

It can be used to give additional rotation on any axis to a particle (and any generated object associated with it) which has been rotated to point along the direction of travel.

Here, in the Tangential mode, with the Tangential Axis set to Z, the Rotation Offset is keyframed to 360 degrees.

Variation

This is used to add variation to the Rotation Offset setting.

This animation has similar settings to the one above, except there is a 180 degree Variation set in the heading.

Spin Around Tangential Axis

This parameter is only available if Rotation Mode is set to Tangential.

Normally, a particle set to tangential rotation cannot also spin; if this setting is enabled, you can spin the particle around the tangential axis.

Spin Amount

Only available if Spin Around Tangential Axis is enabled.

It is the number of degrees to rotate the particle around the tangential axis in each frame.

In this scene, Spin Around Tangential Axis is enabled (with the Tangential Axis set to Z) and a Spin Amount keyframed up to 20 degrees.

Groups Affected tab

Groups

To specify the group, drag and drop the desired Group object into this field.

This setting is useful if you want to ensure that the spawned particles are, or are not, affected by xpSpin.

Mapping tab

The modifier’s settings can be mapped to particle data.

Use the dedicated manual page, below, for instructions on how this works.

Data Mapping

Fields tab

You can use the Fields options to control where xpSpin operates.