Envelopes

Envelopes

Envelopes are how you customize particle animations and animate properties.
An Envelope is essentially an interpolation of a value over time.
An Envelope can control one property of the particle at a time. Some examples are: POS_X, POS_Y, POS_Z, COUNT. (for a full list, see Envelope.PropertyType)

In Partigon, almost everything is an Envelope. Even the parameters that you pass into Envelopes, are Envelopes themselves.

All Envelopes have expressions, which are strings that are evaluated with exp4j.

Envelopes can be nested inside of each other, resulting in unique effects that are otherwise not possible. In these cases, the property type will be PropertyType.NONE.

Most particle animations can be created using one of the already provided Envelope implementations, or using Envelope Wrappers.

All Envelopes extend BasicEnvelope, but you can create your own implementation.

Envelopes have a completion parameter, which indicates how much of the envelope to animate. For example, setting it to 1.0 will animate it in its entirety, 0.5 only half, -1.0 will play it in reverse, etc.

There are several ways to add Envelopes to particles, in order of preference:

1) Constructor-parameter envelopes

positionY = LinearEnvelope(0.0.envelope, 4.0.envelope, RepeatLoop(40))

2) Property type defined in envelope, add with add() extension function

LinearEnvelope(Envelope.PropertyType.POS_Y, 0.0.envelope, 4.0.envelope, RepeatLoop(40)).add()

3) Pass list of envelopes

envelopes = listOf(
    LinearEnvelope(Envelope.PropertyType.POS_Y, 0.0.envelope, 4.0.envelope, RepeatLoop(40))
)