Carbon Flow



Simulation Data node (SOP and DOP).


Connect a Carbon Flow node to a Carbon Simulation node in order to add uniform field or vector field as dynamic flow to the simulation.

Various effects such as wind and turbulence can be achieved through the use of this node.


  • The flow only affects Carbon Cloth and Carbon Rigid Body whose Aerodynamics parameters are not equal to zero.
  • The flow will affect all of those objects even when the flow source (Uniform Field, Vector Field, or VDB volume) contains only 0 values.


If the Carbon Flow node is not applied after a merge, but instead directly after an object, it would most likely be ignored depending on the order of the object connections to the Carbon Simulation node.


A Flow based on a simple Houdini volume.


Input #1: objects

All objects connected to the Carbon Simulation node must also be connected to this input for the Carbon Flow to operate.

Input #2: SOP Vector Field

A Houdini SOP Vector Field import node. This input is ignored when Vector Field is disabled or when a valid Vdb File is specified. Its dataname should always be left unchanged to its default string VectorField. Its import volume must contain a vector field named vel.x vel.y vel.z.


Uniform Field uniformFieldx, uniformFieldy, uniformFieldz

Vector representing a flow uniform value for when the Carbon Flow Vector Field toggle is off.

Vector Field vectorField

Toggle on to enable the SOP Vector Field connected to Input #2 if any.

When this toggle is on the Uniform Field is ignored, even though no SOP Vector Field is connected and no Vdb File is specified.

If a valid Vdb File is specified it will be used as the source for the vector field. Otherwise a valid connected SOP Vector Field will be expected.

Vdb File vdbFile

An OpenVDB vdb file containing the velocity grids named vel.x vel.y vel.z.

Vector Field needs to be toggled on for the vdb file to be used, as otherwise the Uniform Field value takes over.

If both a valid SOP Vector Field is connected and a valid Vdb File is specified, only the content of the Vdb File will be used as the source for the vector field.

Parameter File

Use Parameter File fileOverride

Replace parameter values by expressions fetching the values from the loaded parameter file. Parameter values from the exclusion filter are left unchanged.

File Name fileName

Json file path to save this node’s current parameters to, and load the parameter file from.

Save save

Save this node’s current parameters to the specified file.

Load load

Load or reload the specified parameter file. As the overriding expressions always fetch values from the last loaded parameter file, and not from the file itself, use this button to refresh the loaded current parameter file with the values on disk.

Reload Every Time The Node Is Loaded reload

Automatically reload the parameter file when the scene is loaded. If the specified file cannot be found then the overriding expressions will use the values of the last loaded parameter file instead.

Exclusion Filter exclusionFilter

The exclusion filter allows to select which of the parameters are not to be replaced by the overriding expressions, therefore keeping their original values while all other parameters will evaluate with the values set from the last loaded parameter file.

Guide Geometry

Show Guide Geometry showGuide

Toggle on to enable the visualization of the vectors queried by the Carbon engine.

Vectors are queried for each subdivision, so the number of streamers drawn per frame will vary depending on the Carbon Simulation settings.

Scale scale

Float that represents the scale of the streamer drawn to visualize the queried field values.

Subdivisions subdivisions

Integer that represents the number of samples taken to draw each streamer.

Flow Start colorFlowStartr, colorFlowStartg, colorFlowStartb

Color used as start point to draw the streamer color gradient.

Flow End colorFlowEndr, colorFlowEndg, colorFlowEndb

Color used as end point to draw the streamer color gradient.

See Also