Fan particle node

Applies force on particles like a cone-shaped fan.

All

Parameters

Local variables

Example files

See also: Attractor, Force, Wind

The virtual fan has an origin and applies force radially from its center.

This operator modifies the following attributes: accel.

Using Fan

Select the particle system you want to apply a fan force to.
Click the Fan 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 operator is only active if this value is greater than 0. This is useful to control the effect of this node with an expression.
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.

Fan

Angle	Size of the cone in which the fan has maximum intensity. For example, `90` would create a cone with 45-degree sides. `30` would create a narrow cone, `120` would create a wider cone.
Delta	The number of degrees outside the cone defined by Angle through which the intensity drops from maximum to zero. The higher this number, the greater the falloff area. A value of `0` would make the intensity drop from maximum to 0 at the cone boundary.
Rolloff	How quickly the intensity falls from maximum to 0 in the delta area.
Maximum Distance	The maximum distance at which a particle will be affected by the fan. Set this to `0` to affect all input particles.
Strength	Strength of the fan.
Scale	Scaling factor for the force applied to particles.
Show fan in guide	Graphically show fan parameters when this node is templated.
Guide Scale	Scales the graphical representation of the fan parameters (when Show fan in guide is on and the node is templated). Use this to make the guides more visible when the values are very small.
Show acceleration in guide	Shows particle acceleration as part of the guide geometry when this node is templated.

Location

Reference

The space in which to interpret the locations below.

World space	The locations are in world space.
This object	The locations are relative to the space of the cooking object.
Referenced object	The locations are relative to the object in the Reference object parameter below.

Object

Object space to use, when Reference is “Referenced object”.

Origin

Position of the fan.

Direction

Direction in which the fan is pointing.

Defaults

Ignore Mass	Ignores any mass attributes on the input particles.
Override Mass	Replaces any mass attributes on the input particles with the value of the Mass parameter below.
Mass	Mass to use when Override mass is on.

Noise

The parameters on this tab add randomness to the fan’s force. This makes particles more or less affected at random, creating a less uniform effect.

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.

Hermite Interpolation	Uses splines to interpolate values in the noise field.
Sparse Convolution	More computationally expensive, but produces noise fields free of artifacts present in the Hermite methods.
Improved Hermite	Uses a more linear interpolation than Hermite interpolation.
Alligator Noise	Provides a very different look than the other noise types.

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 `PT` is not constant like `ID`; it changes based on the number of points.
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.

Example files

Fan

$HFS/houdini/help/examples/nodes/pop/fan/Fan.cmd

Load | Launch

This is a simple demonstration of the Fan POP.

Usages in other examples

Example name	Example for