Parameter

On this page, you can set the size of particles and, optionally, how the size changes over the life span of the particles.

Size [-∞..+∞]
Variation [0..100%]

The Size parameter is a multiplier for the size of the particles. For example, a setting of 5 means the particles will become five times larger. You can vary the size of the particles using the Variation parameter.

Over Age
Age Gradient

If Over Age is enabled, you can use the gradient to control the size of particles based on their ages. For example, you can make particles grow larger as they get older. The Age Gradient is especially useful for explosion effects and smoke — smoke or steam spreads and thins out over time.

The left edge of the gradient represents the moment the particles are born and the right edge the moment they die. Thus, the gradient covers the life span of the particles. The brightness at a position on the graph acts as a multiplier for the Size value.

To create a knot, click in an empty area below the gradient and a knot of the color at that position will be added. To change the color of a knot, double-click it and choose the desired color using the system color dialog. To remove a knot, Drag & drop it away from the gradient. The small diamonds on the gradient are bias handles and they pull the interpolation of the color knots from side to side for more control over how the gradient changes. How such gradients work and the effect individual interpolation methods have is explained here.

This example shows how you can affect the size of a particle so its size will vary depending on its speed (the length of the velocity vector). The Math mode is included to produce a single value from the velocity vector and scale the speed down to a sensible value.

Additional input ports:

• Particle

Connect this port to the particle stream that should be re-sized, such as to the Particle output port of a PPass node.

• On

A Boole value of True switches the node on; a value of False switches it off.

• Animation Time

Since the node’s parameters can be keyframe animated, by default the Cinema 4D time is used internally to ensure that the values are interpolated correctly. However, you can pass your own time value to this port. This should be of the data type Time, which is a Real number in the simplest case. If no value is passed, Cinema 4D’s time is used.