Advect by Volumes particle node

Advects particles by a velocity field defined by three volumes.

See also: Force, Wind

The Advect by Volumes POP is designed to make it easy to advect a particle system by a fluid simulation. Often the fluid simulation will be simulated as a separate pass and the velocity fields read of disk. The particles can be live-linked to an existing simulation, however.

This operator modifies the following attributes: accel, vel, P.

Using Advect

Create a particle system by clicking either the Emitter or Source from Geometry tool on the Create Particles shelf.
Create a fluid simulation to affect the way your particles move.
Select the particle system to add advection to.
Click the Advect tool on the Drive Particles tab.
Select the fluid container and press Enter to confirm your selection.

This example shows particles with no velocity being pushed upwards by a smoke simulation.

Parameters

Activation	Turns this node on and off. The operator is only active if this value is greater than 0. This is useful to control the effect of this node with an expression.
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.
Velocity Volumes	The SOP path which has three volumes to be interpreted as the x, y, and z components of the velocity field. These are often the result of importing a velocity field from a fluid simulation. You can directly link to a fluid simulation with something like /obj/AutoDopNetwork:smoke/vel
Velocity Group	Which primitives in the specified SOP are to be the x, y, and z components. The order is important.
Velocity Scale	A uniform scale to apply to the velocity field before any of the force applications.
Advection Type	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.
Force Scale	Scales the force for force update.
Ignore Mass	Treats all particles as having unit mass, ignoring any mass attribute.
Override Mass	Ignore the mass attribute and use the specified mass.
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.
Velocity Blend	In Velocity Blend mode, the amount to mix in the field velocity every timestep.
Velocity Update	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.

Usages in other examples

Example name	Example for