You can control the variation of particles per particle type parameter. By adding variation to a single parameter’s value, you have ultimate control over its specific effect.
To help out with using variance, you can set seed values for many of the variance parameters, as well as setting an overall seed value for all variance parameters in a particle cloud. This allows you to keep all parameter and variance values unchanged so that an effect remains intact, and then change the seed value to modify that effect. This can be very useful if you’re sharing a library of particle effects: they can stay untouched while you simply change the seed value for the cloud.
Setting the Variance (Var) Per Particle Type
Many parameters in the Particle Emitter, Particle Type, and ExplosionOp property editors have Var (Variance) parameters which allow you to add variance to their associated parameter’s value. The Var parameters define the range in which the random numbers are generated.
Variance can be animated, allowing you to have different animations for the parameter’s variance and its value. Variance is animated using two different distribution methods: Uniform and Gaussian.
• With Uniform distribution, random numbers are distributed uniformly around the parameter’s value using the Variance value. The parameter will always be in the range [ Value - Variance; Value + Variance ], never outside of it.
• With Gaussian distribution, random numbers are distributed as a bell curve around the parameter’s value using the Variance value. Most numbers will be in the range [ Value - Variance; Value + Variance ], but they may be outside of that range with [Value - Variance], and they will be outside of that range with [Value + Variance].
If you have the same value for both the parameter itself and the Variance parameter, different numbers result depending on the type of distribution you select. Numbers using Gaussian distribution will have greater variations than the ones using a Uniform distribution.
Sowing Seeds for Particle Types and Clouds
To add a random value to the variance, there are Seed parameters for some particle type Var parameters, as well as a Seed parameter for the particle cloud that affects all Var parameters for the whole simulation. The seed defines which numbers will be generated in the range that the Var parameter specifies. Using a seed, you can change the effect as you like without having to change the parameter’s value or its Var value.
All Seed parameters work only if you have a value other than zero for the Variance parameter to which it is associated.
To set the seed for individual Var parameters
• Set the seed value for the parameters in the Particle Type property pages that have a Var parameter.
• Set the seed value for the emission parameters on the Distribution page in the Emission property editor.
To add a seed to the whole simulation
• Set the Simulation Seed value in the ParticlesOp property editor.
This adds an overall variance factor to all the parameters of the simulation that have a Var parameter. Using this you can, for example, create identical particle clouds and test different results achieved by changing only the simulator seed value.
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