Houdini 16.5 Nodes Particle nodes

Soft Limit POP node

Creates a boundary collisions like Limit, but with spongier bounces.

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This operator gives nicer, less jerky bounces than the Limit and Collision POPs.

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.

Type

Shape of the limit boundary.

Box

Rectangular limit, the corners of which are defined by the +Limit and -Limit parameters below.

Sphere

Spherical limit. The sphere is still defined by a bounding rectangle with the limit parameters below.

+Limit

One corner of the limit’s bounding box. This value should be in the positive quadrant (that is, the X, Y, and Z components are all positive).

-Limit

The other corner of the limit’s bounding box. This value should be in the negative quadrant (that is, the X, Y, and Z components are all negative).

Behavior

Controls how the motion of particles is affected by the collision.

Keep in

Particle stays inside the limit boundary.

Keep out

Particle stays outside the limit boundary.

Force

The constant force that should be applied in the shortest direction out of the sponge.

Dampening

The force is reduced by the component of the particle’s velocity traveling out of the sponge. It is increased by the component traveling into the sponge. This parameter scales the result of that calculation. The total force is never negative.

Stable Drag

Performs a more conservative estimate of the dampening force to ensure the particles don’t overreact and accelerate out of control.

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.

Locals

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.

See also

Particle nodes