Air
This model is useful for making particles that move naturally through air. There are settings for air resistance, turbulence etc.



Motion Path (new in 1.5)
Makes the particles follow a user definable 3D path. The path is defined relative to the "normal" path particles would take if this setting was not used, therefore it is important to move the emitter to where the path actually starts. Read more on how to use Motion Path.



Air Resistance
Makes particle velocity decrease over time. Useful for explosions and fireworks where particles should start with a high velocity and then gradually slow down.

		Off	On

Spin
Particles with spin move in randomized circular orbits. This is useful for adding randomness to particle motion, making it look more natural. It can also be used to create a swarming look (see images below). The Amplitude parameter controls how large the circular orbits are. Frequency is how fast they move in the orbit. Time Before Spin is how long the particle lives before it is fully affected by the spin. The clips below were rendered with motion blur to show the motion clearly:

	Spin Off	Low Frequency	High Frequency

Wind
The wind controls makes all particles move uniformly in the wind direction. The wind controls are keyframable. To make the wind more realistic it can be varied a little over time and also adding some Spin or Turbulence helps increasing realism.

Turbulence Field
Turbulence in Trapcode Particular is a 4D displacement perlin noise fractal (it is not based on fluid dynamics). It adds motion to particles in a way so that particles that are close to each other get a similar, but not equal, random motion. This helps tremendously when creating fire and smoke effects to make particle motion look natural and, unlike fluid dynamics, it computes fast and can be freely scrubbed back and forth in the timeline.



Perlin Noise Fractal Theory
In order to fully comprehend the turbulence functionality some perlin noise fractal theory helps. Perlin noise was invented by Ken Perlin (kudos to Mr. Perlin, this is amazing stuff!). Perlin noise is a quick way to produce a pseudo-random field that can be of any dimensionality (1D, 2D, 3D etc...). The field is "smooth" and can look something like this (2D):



If the same field is scaled down (or "zoomed out"), it looks something like this:



Now, if a couple of these fields with different scales are added together they form what is called a Perlin Noise Fractal:



The number of fields added together is called Complexity (if three fields are added together complexity equals three). The difference in scale for each field is called Octave Scale and the difference in influence for each field is called Octave Multiplier. The images above were created using Adobe After Effects built-in perlin noise fractal generator (Effect>Noise>Fractal Noise).

The really interesting part is that these fractals can be evolved over time. What is seen in the images above is actually a cross section of a 3D perlin noise fractal. The cross section can slide through 3D space and thus create a smoothly evolving 2D pattern. This parameter is called Evolution.

However, in Trapcode Particular a 3D displacement field is needed, so that means the perlin noise fractal has to be 4D so it can be smoothly evolved (by sliding the 3D cross-section in 4D space). Ok, enough with the theory and back to the parameters in Trapcode Particular!

Affect Size
This parameter enables using the fractal for particle size distortion. Setting up this parameter means the fractal field will be sampled at each particle's location and the size of that particle will be affected by the value of the field. This can be useful for creating cloud-like particle clusters:

Affect Size Off	Affect Size On

Affect Postion
Use the fractal to displace particle position. This is useful for creating natural looking motion for fire and smoke effects. Notice how different it is to Spin (above):

	Affect Position Off	Low Scale	High Scale

Time Before Affect
Sets the time before the particles are fully affected by the turbulence field.

Scale
The overall scale of the fractal. See animations for Affect Position above

Complexity
The number of Perlin noise fields added together to form the fractal.

Octave Multiplier
The influence of each added noise field compared to the previous.

Octave Scale
The scale of each added noise field compared to the previous.

Evolution Speed
How fast the turbulence field evolves over time.

Move with Wind [%]
Gives the ability to move the turbulence field with the wind. Gives a very realistic look to fire and smoke effects.



Spherical Field
This is a displacement field in the form of a sphere. The sphere can either push particles outward or suck them in. This is not a force field, the effect of the field is instant and as soon as the field is removed everything looks like it never existed.



Strength
Positive values gives a field that pushes particles outward. Negative values means particles get sucked inward.

	Strength Zero	Strength Positive	Strength Negative

Position XY & Z
The position of the field.

Radius
The size of the field

Feather
Softness of the edges of the field

Visualize Field
Check this to get a visualization of the field. Useful when setting up the field.