SurfaceForce is a true particle force operator that uses mesh information to generate a Force or Velocity displacement of particles. The mesh used as surface force can be animated either by translation or deformation. Both animation methods will have an effect on the particles.

Operator Inputs

ON - (Bool) This input data stream determines whether the operator is considered 'on' or 'off'. You can connect other operators to this input channel such as a Bool Helper to activate/deactivate the whole operator.

Time - (Time) This input data stream is used to define the local time for the operator when the user wants to override the default system time.

Particle - (Particle) connect particles to this input which should be affected by SurfaceForce.


Using the particle input is not recommended. This operator can work in multi-threaded mode when supplying the particle group from within the UI drction and not when using the particle input.

UI Control Parameters - those input data streams are the equivalent of the UI controls, keep in mind that there is no visual indication that an operator is connected to any of those inputs! It might be needless to adjust a value if it gets overwritten by a connected operator.

Operator Outputs

No outputs available for this Node

Rollout Menu

SurfaceForce Objects - this list box holds the selected 3ds Max objects that will act as a particle force.

Add - press this button to start a standard 3ds Max pick object operation

Remove - click this button to remove the selected object from the list

Group - defines the particle group to be affected by the SurfaceForce. Using this option is the preferred method even though the particle input of this node could also be used to achieve the exact same result. However, only when you select a particle Group through this user interface option the calculations will be fully multi-threaded.

Include Subgroups - when checked, the subgroups are also considered when applying the forces to the particles.

Object Axis - defines the main axis to be used by the surface force object. The force will be applied to each particle by finding the resulting vector towards the surface of the object.

Side - defines the intersection test to be either with the front surface, back surface or both sides. (indicated when SHOW is used)

Set As - defines how particles will be displaced in space. There are 2 options:

Force - when checked, a standard additive force will be applied

Velocity - check this option to have a relative velocity change applied.

Type - lets you specify how the surface change should affect the object.

Pressure - defines a force that is directed horizontally along the surface. The surface needs a change in height. This option creates a force direction that is left to right and not up to down. The surface force mesh must be animated to work!

Move - creates a force which acts in the opposite direction of pressure. Moving the particles along the surface. The surface force mesh must be animated to work!

Lift - defines a force that lifts particles up based on the speed of the surface and force multiplier. The surface force mesh must be animated to work!

Normal Const. - sets a constant force which creates a kind of displacement towards the particles. No animation is needed. This type can be used to simulate standing wave patterns.

Pressure Const.- creates a constant force, applied to the particles.

Intensity -sets the strength of the force or velocity that will be applied.

Parallel - allows to add an extra force parallel to the specified axis

Tangential - allows to add an extra force tangential to the specified axis

Directional - adds an overall directional force to the particles.

Direction - defines the direction vector of the directional force. This is an angle in degrees (360 is a full circle). Orientation is clock wise.

Attenuation - by default forces have an unlimited reach. Check this option to attenuate the force effect by distance to the surface of the object.

End - sets the distance at which the right hand color of the attenuation gradient will be used for all further away particles.

Near/Far - sets the near and far multiplier value for the for the force attenuation.

Show - check this option to enable the viewport visualization of the various forces available with this operator. Several options are available:

None - when set no viewport visualization is displayed

Force Sum - select this option to visualize the resulting force vector

Type - select this option to visualize the selected force type

Paralell -select this option to visualize the parallel force vector

Tangential - select this option to visualize the tangential force vector

Directional - select this option to visualize the directional force vector

Attenuation - select this option to visualize the attenuation force vector

Scale - sets a scale factor for the vectors used to visualize the forces