The Curl Noise POP is designed to apply a divergent free noise field to particles. A divergent free field has no "sinks" or "sources" so particles will move turbulently without accumulating in any location.
Extra advection options are possible to directly set the velocity or position attribute to add layers of passive curl noise without affecting the particle’s acceleration.
This is a common POP to add to FLIP fluid simulations, since it plays very predictably with any fluid simulations that contains a Gas Project Non-Divergence DOP.
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.
Specifies the noise type.
Standard noise which performs a 3 dimensional hermite spline interpolation on a lattice of random values.
Original Perlin Noise
Similar to Perlin Noise, but marginally less efficient in computation and with different characteristics.
Sparse Convolution Noise
Slower, more random.
Slow, cell-like noise.
Noise based on a tetrahedral mesh rather than a grid, with better derivatives.
Analytic Perlin Noise, Simplex Noise
These are faster versions of the noise that do not use the step size to compute the noise, but rather evaluate it directly.
Allows the noise field to be effectively moved through space.
The scale of the noise. Decreasing frequency increases feature size.
Controls the resolution of the curl function used to generate the noise. A lower value will lead to tighter spirals in the noise.
Maximum value of noise field.
Raises the noise to the given exponent.
Number of iterations of fractal noise to add.
Scale of noise added with each iteration.
A volume that is a signed distance field used for collision calculations. The turbulence is damped near the collision object to prevent particles from passing through.
When particles cross the SDF boundary they have their velocities reversed according to the SDF normal and are pushed outside of the SDF.
Collision Effect Radius
The distance at which the particles start to slow down due to a collision object.
The noise will be a 4d noise that changes over time.
How long in seconds for the noise to complete change itself.
There are several different ways to update a particle system in response to an external velocity field. They are broadly categorized as Force, Velocity, and Position updates.
The Force Update will adjust the acceleration of the particles according to their mass, the force scale, and the velocity field. This acts like the Force POP.
Blend Velocity directly changes the velocity of the particles by blending in the velocity field causing them to swiftly match the velocity field.
Position Update directly moves the velocity positions. This is useful as it allows the particles own velocity to be considered independently of the bulk fluid velocity. Position Update is similar to what the Gas Advect DOP would perform.
Scales the force for force update.
Treats all particles as having unit mass, ignoring any mass attribute.
Ignore the mass attribute and use the specified mass.
The mass to use if mass is overridden.
Treat As Wind
Instead of applying a force in the direction of the velocity field, the force is applied relative to the difference between the particle’s velocity and the velocity field. This effectively adds an implicit drag that causes the particles to match the velocity field.
In Velocity Blend mode, the amount to mix in the field velocity every timestep.
In Velocity Blend mode, the amount to add the curlnoise velocity to the particle’s velocity. This can be useful in addition to advectbyvolume to layer turbulence on a velocity field.
In Position Update mode it is possible to read in the velocity from the velocity field. Note that the resulting velocity will be used by the particle integrator, so unless something special is done this could result in double-moving the particle.
Number of threads
The number of threads to create to process the VEX commands. If you have multiple processors, this can speed up processing of the node.
Do not perform parallel processing.
One per processor
Create one thread for each processor in your computer.
Create two threads.