Spin Modifier

Summary

This modifier spins or rotates the particles.

Note that this modifier is not required if all you want to do is set a particle spinning. For this, it is much simpler to use the 'Simple Spin' settings in the emitter's Emission tab.

Interface

This modifier has two modes of operation:

In addition there are some parameters common to both modes.

For the 'Groups Affected', 'Mapping', and 'Falloff' tabs, and for the buttons at the bottom of the interface, please see the 'Common interface elements' page.

Parameters

Common to both modes

Enabled

Uncheck this switch to disable the modifier.

Mode

Independent [default setting]

In this mode, the modifier will work in the same way as a standard Cinema 4D particle modifier: particles will be affected if they come into the field of effect of the modifier. X-Particle Actions have no effect on the modifier in this mode.

Action-Controlled

In this mode, the modifier will only act on a particle when told to do so by an Action. Until that point, the particle will not be affected, but once activated for a particular particle, the modifier will continue to influence it as long as it is in the field of effect of the modifier. The modifier's effect on a particle can be halted by means of another Action, if desired.

Operation

This modifier has two modes of operation. The default is 'Spin' and with this selected it will behave as it did in previous versions of X-Particles. The other mode is 'Rotate' which as it name suggests does not spin a particle but rotates it to a specified value.

The drop-down menu therefore has two options:

Spin

The modifier spins the particles. Note, however that the 'Simple Spin' setting in the emitter is now overridden by a Spin modifier set to this mode. That is, if simple spin is enabled but this modifier 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 options are available in this mode (see below).

Parameters when Operation is set to Spin

Very important: to use this modifier in 'Spin' mode, you must first ensure that the particle has created the necessary data structure to handle particle rotations. You do this by turning on 'Use Rotation' in the Emitter object Extended Data tab, 'Particle Rotation' section. 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 (very important with millions of particles!).These are shown in the screenshot above.

Spin Time

This drop-down menu has two options:

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. The full amount of spin is applied to particles passing through the modifier’s red zone; those in the yellow zone have their spin altered in a reduced amount, depending on the strength of the falloff.

Increment Spin

This switch 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). Check this button to gain access to the increment value field and to increase the spin each frame.

Increment Value

If the 'Increment Spin' switch is checked, 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, for example. 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!

Note: you should use very small values in this field! Typically values of 0.1 to 0.3 degrees give good results (negative values are allowed). If the value is too high, the change in spin will appear to be instantaneous (which might be what you want, of course).

Clamp Spin, Clamp To

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

Randomise Spin, Random Spin Value

To give a particle a random spin, check this box. The particle will then spin in either direction by a random value.

Unidirectional

This option is only available if 'Randomise Spin' is selected. 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, check this switch. The spin can be reversed by using a negative value in 'Random Spin Value'.

Parameters when Operation is set to Rotate

Note: this mode does NOT require that 'Use Rotation' is enabled in the emitter. Unlike 'Spin' mode, this will work whether or not that option is checked.

In this mode these parameters are shown:

Rotation Mode

This drop-down has four options:

Absolute

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

Relative

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

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.

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.

Object

The object to point at, in 'Face Object' mode.

Rotation

The rotation value used in 'Absolute' or 'Relative' modes.

Use Time

This switch is only available in 'Absolute' or 'Relative' modes. If checked, the change in rotation will take place over the time given in the 'Time' field.

Time

This switch is only available in 'Absolute' or 'Relative' modes and when 'Use Time' is checked. 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 unchecked).