For any of the animation controls to have effect, you must first animate the parameter (that is, you must first key its values to create a function curve). The different control modes only define how to interpret that function curve.
Animating Particle Type Parameters
You can add realism to your particle simulation by animating certain particle values such as speed, color, and the influence of environmental forces. Particle values can change as a function of their own lifetime or as a function of the lifetime of the particle simulation itself. This lets you create effects such as making particles change color as they age or having all particles suddenly accelerate at a given point in time.
Particle parameters that are animatable have a list of control modes that lets you specify how they can be animated: Birth, Age, Age %, or Absolute.
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For any of the animation controls to have effect, you must first animate the parameter (that is, you must first key its values to create a function curve). The different control modes only define how to interpret that function curve. |
In Birth mode, the value of the parameter’s function curve at birth time is kept constant over its lifetime (Max Life value).
For example, particles retain whatever color is defined at time of their birth and stay that color until they die. Using this method, you could layer different colors by setting different lifetimes for each colored particle.
Abs(olute) is the same as Birth mode, but instead of keeping the value parameter constant, it evolves according to its function curve over the particle’s lifetime (Max Life value). This means that all particles get the same value over time independently from their age.
All of the particles change at the same time, no matter where they are in their lifetime. Think of filming some smoke with a regular lens on your camera, then adding a blue lens filter: all the smoke particles change color at the same time.
When the particle is born, the value of the parameter that corresponds to the function curve at the start frame of the simulation is used. Then the associated value evolves according to its function curve over the particle’s lifetime (Max Life value).
Transitions that you key happen at the frame you key them and continue to change throughout the lifetime of the particle. It happens based on the particles’ individual ages and occurs separately for all of them.
Also, Age lets you have transitions that do not happen if the frame they are keyed at does not fall within the particle’s lifetime. For example, if you key a transition at frame 50 but the particle dies at frame 35, you would have to increase the lifetime or move the key to be within the lifetime to see that transition.
Age % uses function curve values defined by the particle type Size or the Color’s RGB and/or Alpha controls to map a shift range between 0 and 100% (a percentage of the particle’s lifetime). This creates a size or color shift effect over a particle’s lifetime (Max Life) that corresponds to the values defined by the keys. It refers to the percentage of the particle’s age as opposed to a particular keyframe, as Age does.
When you use Age %, keying the size or color over 100 frames gives you more predictable results because each frame represents a percentage point (one percentage point for every 10 frames). Then, for example, if you want the particle to change color or size halfway through its lifetime, you would key it at frame 50.
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Always key the parameter’s values in another animation mode and then switch to Age % when you’re done. |
Creating a Size Shift with Age %
This example shows you how to create a shift by keying the particle type’s Size and then using the Age % mode to compress the animation into the particle’s lifetime.
1. Select a particle type and open the Particle Type property editor.
2. On the General page, set the Size to 0.2.
3. Go to frame 1 and click the Size’s animation icon to set a key for this value.
4. Go to frame 90, change the size to 2 and set a key for this value.
5. Select Age % as the method of animation for Size.
Now the size shifts within the lifetime of the particle (Max Life), not over the whole simulation of 100 frames (meaning that you can change the particle’s lifetime and the shift will retain the same proportions).
6. Right-click the Size parameter’s animation icon and choose Animation Editor to see the age percentage function curves for the Size parameter.
Note: The fcurves are expressed in seconds, not in frames. 100 frames corresponds to 3.333 seconds if you are at 30 fps or 4.17 if you are at 24 fps.
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