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### 3.2.6 Standard Particle Affectors

Ogre comes preconfigured with a few particle affectors. New ones can be added by creating plugins: see the Plugin_ParticleFX project as an example of how you would do this (this is where these affectors are implemented).

- Linear Force Affector
- ColourFader Affector
- Scaler Affector

### Linear Force Affector

This affector applies a force vector to all particles to modify their trajectory. Can be used for gravity, wind, or any other linear force. It's extra attributes are:

force_vector
  Sets the vector for the force to be applied to every particle. The magnitude of this vector determines how strong the force is.
  format: force_vector <x> <y> <z>
  example: force_vector 50 0 -50
  default: 0 -100 0 (a fair gravity effect)
force_application

  Sets the way in which the force vector is applied to particle momentum.
  format: force_application <add|average>
  example: force_application average
  default: add
  The options are:

  average
    The resulting momentum is the average of the force vector and the particle's current motion. Is self-stabilising but the speed at which the particle changes direction is non-linear.
  add
    The resulting momentum is the particle's current motion plus the force vector. This is traditional force acceleration but can potentially result in unlimited velocity.

To create a linear force affector, include a section like this within your particle system script:

    affector LinearForce
    {
        // Settings go here
    }

Please note that the name of the affector type ('LinearForce') is case-sensitive.

### ColourFader Affector

This affector modifies the colour of particles in flight. It's extra attributes are:

red
  Sets the adjustment to be made to the red component of the particle colour per second.
  format: red <delta_value>
  example: red -0.1
  default: 0
green
  Sets the adjustment to be made to the green component of the particle colour per second.
  format: green <delta_value>
  example: green -0.1
  default: 0
blue
  Sets the adjustment to be made to the blue component of the particle colour per second.
  format: blue <delta_value>
  example: blue -0.1
  default: 0
alpha
  Sets the adjustment to be made to the alpha component of the particle colour per second.
  format: alpha <delta_value>
  example: alpha -0.1
  default: 0

To create a colour fader affector, include a section like this within your particle system script:

    affector ColourFader
    {
        // Settings go here
    }

### Scaler Affector

This affector scales particles in flight. It's extra attributes are:

rate
  The amount by which to scale the particles in both the x and y direction per second.

To create a scale affector, include a section like this within your particle system script:

    affector Scaler
    {
        // Settings go here
    }

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This document was generated by Steve Streeting on , 28 2004 using texi2html