NAVIÉ
Documentation : Effex : Objects : Particles : Particle Group

### Passive Particles

Passive Particles Liquid Particles Vorticity Particles Diffuse Particles
Passive Particles

Passive particles have the purpose of providing the user with a custom particle system that can either be passively advected by a velocity field (fluid dynamics) or as ballistic particles (replacing the old Simple Particles).

Passive Particles::Display
Contains all the settings for the display of particles in the editor view.

#### Draw each Xth particle

Allows to set an interval for drawing particles. A value of 0 will turn off the display of particles.
A value of 1 will display all particles, a value of 2 will draw each second particle and so on.

#### Color

The display color of this particle type.

#### Size

This option, if set > 0.0, will create for each particle a sphere render instance of the specified size.

#### Advection

Defines how the particles are advected.
Off
No advection takes place. Use this if you want to have static particles or if you want to advect them yourself.
Dynamics
Advection is done by an external velocity field (fluid dynamics).
Ballistic
Ballistic advection. No reaction to fluid dynamics and/or grid forces. Particle forces can directly be used on them though.
Dynamics & Ballistic outside
Advection is done by an external velocity field (fluid dynamics) if the particles are inside of a fluid container domain. Outside of it, the particles switch to ballistic advection. This allows to have the particles keep on moving outside the grid domain.

#### Advect by Fluids

If the particles are inside of a gaseous fluids domain, they are advected by the according velocity field.

#### Advect by Liquids

If the particles are inside of a liquid fluids domain they are advected by the according velocity field.

#### Volume Collision

Defines the collision with any volumes in the Effex scene.
Off
No collisions are calculated.
Obstacles
Collides with all volumes that have an obstacle tag attached. You would use this mode if you don't have any fluid dynamics in the scene and/or the particles are ballistic.
Obstacles (Fluid Dynamics domain)
Collides with the obstacles field defined inside of a fluid dynamics domain (the fluid dynamics generate an optimised version of all obstacles in the effex scene so collisions can be calculated faster.

#### Instants

Instants are evaluated when a certain event takes place. In this case the particle-volume collision event will trigger instant operators.
Drop any instant operators in here to let them do their thing on particles when they do collide.

#### Kill outside containers

If particles leave a used fluid dynamics container, this setting (activated) will let the particles die instantly.

#### Integrator

Defines how the advection (moving the particles around inside the grid based on the velocity field) in time and space is integrated.
The higher the order number, the more accurate the integration will be.
In order of quality:
Euler 1st Order
Runga-Kutta 2nd Order
Runga-Kutta 3rd Order
Runge-Kutta 4th Order (best)

#### Ballistic Integration

Defines how the ballistic advection (moving the particles around according to any external particle forces) in time and space is integrated.
Euler
Advects particles using a special Euler intergrator. This integration is based on the position and velocity of the particles.
Any available external force property is also taken into account.
Verlet
Advects particles using a Verlet integrator. This integration is based on the position of the particles only. This is the same integrator that was used for the former Simple Particles.

#### Advection Substeps

How many substeps should be taken per advection step. Can improve accuracy.

#### Exclude & Fluid Dynamics

The drop down lets you decide if the below Fluid Dynamics list and any of its entries are excluded or included from being used in the particle advection step.

#### Particle Forces

Drop in here any Particle Forces or Dual Forces that shall act on the particles in this subgroup.