Rotates particles around another point.
Torque is expressed as a force applied to a position relative to the particle’s frame of reference. You specify an offset from the particle, and a direction and magnitude to apply to that offset point. As the offset position moves, the particle’s frame of reference (and so any instanced geometry) rotates with it.
Torque is to Angular Velocity what Force is to Velocity.
Because the Position and Force parameters are in the particle's frame of reference, given the same position and force values, the particle will have the same rotation at each step.
Use the 
Rotation POP if you want to rotate particle frame of reference using angular values instead of torque.
Tip
To see the effect of this operator in the viewer, turn on the particle axes option in the viewer’s display options. This lets you see the particle’s frame of reference rotating.
This operator modifies the torque attribute.
Using Torque
Select the
particle system you want to be affected.
Click the
Torque tool on the Drive Particles tab.
Specify the node settings in the operation controls toolbar or parameter editor.
Parameters
| Activation | Turns this node on and off. The node is only active if this value is greater than 0. This is useful to control the effect of this node with an expression. Note that this is activation of the node as a whole. You can’t use this parameter to deactivate the node for certain particles. |
| Source Group | Only affect a group of points (created with, for example, a Group POP or Collision POP) out of all the points in the input. |
Torque
| Force | Force magnitude A vector describing the force direction and magnitude. The direction of the vector controls the direction of the force, and the length of the vector controls the intensity of the force. For example, a value of (0, 1, 0) would create a force straight up. A value of (0, 2, 0) would represent force in the same direction but twice as strong. |
| Position | Offset position at which to apply the force. The farther away from the center, the greater the torque. The combination of the force direction and the offset direction determine the axis of spin which the torque will induce. The particle will have a torque causing it to spin around an axis perpendicular to both the offset position and the force direction. |
| Scale | Overall force scaling factor. |
Noise
The parameters on this tab add randomness to the torque. This makes particles more or less affected by the torque at random, creating a less uniform effect. The randomness is added to the Force vector prior to the calculation of the torque.
| Seed | Seed value for the random turbulence generator. | ||||||||
| Turbulence | Number of iterations of fractal noise to add. | ||||||||
| Roughness | Scale of noise added with each iteration. | ||||||||
| Exponent | Noise attenuation exponent. | ||||||||
| Frequency | Spatial frequency of noise field in X, Y, and Z. | ||||||||
| Amplitude | Maximum value of noise field. | ||||||||
| Offset | Amount to shift noise along X, Y, and Z axes. | ||||||||
| Noise Type | Method used to generate noise. Hermite Interpolation and Improved Hermite are fastest.
|
Local variables
Standard POP local variables
| AGE | The seconds a particle in the template has been alive. |
| AX AY AZ | Acceleration of the particle. |
| BBX BBY BBZ | The point’s relative position in the bounding box. |
| DEAD | Point is dead. |
| ITER | Processing iteration number. |
| JUSTHIT | A collision for this particle was detected (for example, by the Collision POP) during the processing of this timestep (that is, this iteration of the particle simulation). This variable is cleared at the beginning of each timestep. Note that the collision POP actually detects any collisions which would have occurred the during the previous frame. |
| LIFE | Percent of total life used (from 0 to 1). |
| LIFESPAN | Expected lifetime of particle. |
| MAPU MAPV MAPW | Point or vertex texture coordinates. |
| NPT | Total number of points. |
| NGRP | Total number of points in source group. |
| NX NY NZ | Normal vector. |
| PT | The point number of the currently processed point. The |
| RESTX RESTY RESTZ | The rest position. |
| SLIDING | The sliding state of the particle. |
| SPRINGK | Elasticity of a point. |
| STOPPED | Point is stopped. |
| STUCK | 1 if particle is stuck to a collision object. |
| TENSION | Spring tension. |
| TIMEINC | Time increment. |
| TX TY TZ | Point position. |
| U V | Surface UV values. |
| VX VY VZ | Velocity direction. |
| WEIGHT | Point spline weight. |
Added by Collision POP/Limit POP
| DIST | Distance from particle to last collision. |
| HCR HCG HCB | Diffuse color at the collision point on the surface the particle collided with. |
| HITID | ID for last collision. You can control how this attribute is set in the Collision or Limit POP to help distinguish types of collisions. |
| HITTIME | The time at which the last collision occurred. |
| HMAPU HMAPV | The texture map UV coordinates for the surface location where the last collision occurred. |
| HNX HNY HNZ | The normal at the surface location where the last collision occurred. |
| HTX HTY HTZ | World space position of the last collision. |
| HU HV | The UV coordinates for the surface location where the last collision occurred. |
| NUMHIT | Number of times the particle has collided. |
Added by Color POP
| CA | Point or vertex alpha value. |
| CR CG CB | Diffuse point or vertex color. |
Added by Property POP
| ATTRACT | Attractor point. |
| CHARGE | Charge of the particle. |
| CLING | Point is clinging to geometry. |
| DRAG | Point drag. |
| FOLLOW | Leader to follow. |
| MASS | Point mass. |
| PSCALE | Particle Scale. |
| SCALEX SCALEY SCALEZ | Non-uniform scale. |
Added by Proximity POP
| NEAREST | Either the point number or id of the particle nearest to this one. |
| NEARESTDIST | The distance to the nearest particle. |
| NUMPROXIMITY | The number of particles within a specified proximity to this particle. |
Added by Rotation POP
| ROTA | Rotation angle. |
| ROTX ROTY ROTZ | Rotation axis. |
Added by Source POP
| GEN | Generation. |
| ID | ID number, which always remains constant. |
| ORIGIN | Original Source point was birthed from. |
| PARENT | Parent’s ID Number. |
Added by Speed Limit POP
| SPEEDMAX | Maximum speed. |
| SPEEDMIN | Minimum speed. |
Added by Sprite POP
| SROT | Sprite rotation around view axis (in degrees). |
| STEXU STEXV | Texture coordinate of sprite’s lower-left corner. |
| STEXW STEXH | Size of sprite in texture space. |
| SX SY | Sprite scale. |
Controlled by Suppress Rule POP
| SUPPPOS | Suppress default position rule. |
| SUPPVEL | Suppress default velocity rule. |
| SUPPUP | Suppress default up-vector rule. |
| SUPPAGE | Suppress default aging rule. |
| SUPPROT | 1 if particle is suppressing its default rotation rule. |
| SUPPANGVEL | 1 if particle is suppressing its default angular velocity rule. |
Added by Up Vector POP
| PVX PVY PVZ | Previous velocity. |
| UPX UPY UPZ | Up vector. |
Added by Location, Source, Softbody, Split POPs
| SPEED | Absolute speed of particle. |
Examples
| TorqueBox | Load | Launch |
This example file uses the Torque POP to control the rotation of a Polygonal Cube. The Torque POP works by applying a force to a particle’s axis. The axis is then rotated according to the parameters dictated by that force. Press Play to view the animation. | |