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Fast Physics offers two kinds of displacement models to push along the particles. One is Turbulence Field, based on a 3D displacement of a Perlin Noise fractal. Turbulence adds motion so particles that are close to each other get a similar, but not equal, random motion.
This behavior helps tremendously when creating fire and smoke effects to make particle motion look natural. Turbulence computes fast and can be freely scrubbed back and forth in the Timeline.
If you want to know about the inner workings of Turbulence Field, go to the end of this page to read about Perlin Fractal Noise.
TF Affect Size 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 |
TF Affect Position uses the fractal to displace particle position. This is useful for creating natural looking motion for fire and smoke effects. Notice how different it is from Spin.
Off |
Low Scale | High Scale |
TF Affect Size 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 Opacity Off |
Affect Opacity On |
Fade-in Time sets the amount of time in seconds before the particles are fully affected by the Turbulence Field. High values means the Turbulence takes a while to affect the particles, which makes the animation fade in gradually over time.
This is a fade-in curve control for Turbulence Field. Smooth is on by default, and fades in the field more subtly. Linear gives a linear interpolation to the curve, which can sometimes produces a jerk in the animation.
A group that gives you control over the underlying fractal driving the Turbulence Field offsets.
TF Move with Wind gives the ability to move the Turbulence Field with the Wind X, Y, Z controls in Environment. Measured as a percentage of the Wind value. At 100%, the Turbulence Field follows the Wind exactly. At 50%, it still follows the Wind's direction, but only 50% of the distance.
This control gives a very realistic look to fire and smoke effects. It is useful for getting a natural look in making wind, since the Turbulence Field moves with the wind as it would in real life.
TF Move with Drift gives the ability to move the Turbulence Field with the Drift X, Y, Z controls in Fast Physics. Measured as a percentage of the Drift value. At 100%, the Turbulence Field follows the Drift exactly. At 50%, it still follows the Drift's direction, but only 50% of the distance.
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. For example, 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 of Perlin Noise 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. In Trapcode Particular, a 3D displacement field is needed. This requires the Perlin Noise fractal to be 4D so it can smoothly evolve by sliding the 3D cross-section in time. And now you've been initiated into Fractal Noise Theory!