Force surface node

Uses a metaball to attract or repel particles or springs.

All

Parameters

Inputs

Example files

See also: Metaball

This node adds force attributes to a metaball field which make the field attract or repel particles or springs created by the Spring node.

In general, force values greater than 0 cause points to be attracted, less than 0 cause points to be repelled.

You can use this node in conjunction with a Particle SOP to create natural particle simulations of whirlwinds, tornadoes, water swirling down a drain, and so on.

Tip

To view the metaball field of influence, turn on the hulls display of the input metaball/s object/s. Both the Particle SOP and Spring SOP will display these hulls as guide geometry.

Tip

Adjust the weights of the metaball inputs to increase or decrease the field effect within the metaball field of influence.

Tip

In general, it is a good idea to try and keep the scale of forces and force fields to a smaller rather than a larger scale. This tends to make particle movement and attraction more manageable and realistic.

Parameters

Radial Force

Overview	Triggers force to radius of metaball field.
Force	Controls the strength of the radial force.

Directional Force

Overview	Allows control of force attributes.
Direction	Primary axis of metaball field.
Axial Force	Force along primary axis of field.
Vortex Force	Amount of twist around primary axis.
Spiral Force	Attraction force perpendicular to axis.

Inputs

Input 1

This node only accepts metaballs. Connecting a non-metaball SOP has no effect.

Example files

ForceBasic

$HFS/houdini/help/examples/nodes/sop/force/ForceBasic.cmd

Load | Launch

This example file uses the Force SOP in conjunction with Metaball SOPs and Particle SOPs to create dynamic animations.

Using the Radial Force Parameter of the Force SOP, particles are puffed in and out. Then, using the Directional Force Parameter, a rotating vortex is created as a metaball spins around an axis.

Press play to view the animation.

Usages in other examples

Example name	Example for
SpringHair	Spring surface node	Load \| Launch
ParticleAttractor	Particle surface node	Load \| Launch
ParticleDisturbance	Particle surface node	Load \| Launch
ParticlePusher	Particle surface node	Load \| Launch
ParticleExamples	Particle surface node	Load \| Launch
SparksStream	Stream particle node	Load \| Launch