Spin
Use this percentage value to control the effect of the modifier on the particles. At 0% the particles remain unaffected and at 100% the full effect of the modifier is transferred to the particles. Intermediate values lead to a corresponding mixture of the current particle property and modifier property.
This is where you select how the rotation should be implemented:
- Set: In this mode, a continuous rotational speed around the Z-axis of the particle systems is transferred(Set: Speed) or (with Set: Spin Vector) a direction of rotation is defined. These properties can also be combined if two Turn modifiers act on the particles one after the other. The modifier that acts first determines the rotation speed of the particles by Set Speed. The second Turn modifier then uses the Set Turn vector combination and controls the direction of the rotation axis.
- Turn: In this mode, a rotation angle can be defined that is applied either per animation frame or per second of the animation. This function is similar to the corresponding mode on the Look modifier. The direction of the rotation axis can be configured using the separate Spin Vector setting.
If you select Turn mode, you can define the desired rotation angle here. The speed at which this angle is transferred to the particles is determined by the corresponding mode selection:
- Per Frame: The set angle is transferred to the particles per animation image. This often results in small Angles being used, which then lead to a uniform rotational speed of the particle systems, for example.
- Per second: The set Angle is applied to the particles over the course of one animation second.
These settings are only available in Set mode and allow you to either define a rotation speed per second around the Z-axis of the particles or to define a direction for the rotation axis:
- Speed: A rotation speed (rotation angle per second) can be defined via the Speed value. Rotation takes place around the Z-axis of the particle axis system. The direction of the particle axis system cannot be influenced in this mode, but you can use a second Rotate or Align modifier, for example, and apply it to the same particles.
- Rotation vector: In this mode, only the direction of the rotation axis can be influenced, not the rotation speed itself.
For the Set speed mode combination, you can use this to define the desired speed that should be applied per second of the animation for the rotation. The subordinate Spread value can be used to define a deviation from this speed per particle. Rotation generally takes place around the Z-axis of the particle systems.
The rotation of the particles takes place around this direction, which can be defined in the Set Forward vector or Turn modes. The reference system for this can be influenced for the rotation vectors Axis, Speed direction and User-defined via the separate Vector Space setting.
- Axis: You can define one of the particle axes or one of the global axis directions for the rotations.
- Velocity Direction: The particle rotation will take place around the direction of flight of the particles. This would, for example, be the usual direction of rotation for a projectile that will be stabilized by this rotation during flight.
- Random: The axis of rotation will be ascertained randomly for each particle. As with all randomness, this calculation is also based on the Seed value. A change in the Seed value will also lead to a recalculation of the axes of rotation.
- Custom: You can define any Vector to be used as the rotation axis. The length of this vector is irrelevant. The vector can be evaluated either in the system of the particle or in the global world system.
- Target: Here you link any object whose position will be evaluated. The direction between each particle and the defined object position will be used as the axis of rotation.
For the Spin Vector Axis, select one of the standard axis directions around which the particles should rotate. This axis can be selected via Vector Space either in the axis system of the particle or in the global world system.
In Custom Spin Vector mode, you can define your own direction vector here to be used as the rotation axis of the particles. The length of this vector is irrelevant. This vector can be selected via the Vector Space setting either relative to the axis system of the particle or relative to the global world axes.
In Spin Vector mode Target, you can link to an object here. The connecting line between each particle and the position of this object will be used as the axis of rotation.
The Turn Vector in the Axis, Velocity Direction and Custom modes can be selected either relative to the axis system of the particle (see Look modifier) or relative to the global axis system (Global).
Here you can define a maximum variation for the direction of the axes of rotation. As with all random variation values, this calculation is also based on the Seed value of the emitter. A new Seed value will also lead to a new variation of the axes of rotation.
This value controls the relationship between the rotational axes varied by Spread and the original Spin Vector of the particles. The greater the decrease in Spread, the closer the rotation vectors of the particles return to their original direction. The greatest possible spread of the axes of rotation can be achieved with a value of 0%.
The calculation of all randomness of the Modifier will be based on this value. A change in the Seed value will also lead to a recalculation of all activated variations, such as the Spread.