ADSR (Attack, Decay, Sustain, Release) envelopes and tools.
Attack, decay, sustain, release.
Demonstrates how to use an ADSRTracker.
The ADSRTracker keeps a collection of active ADSR envelopes.
An ADSR envelope is commonly used in musical synthesizers to track the volume of a sound produced in response to pressing, holding and releasing a key in it keyboard.
The ADSR envelope in OPENRNDR, when triggerOn is called, tracks the change of a
Double value increasing from 0.0 to 1.0 in attack seconds,
then decays to the sustain level in decay seconds, and finally when
triggerOff is called, decreases back to 0.0 in release seconds.
The time in seconds is tracked by a Clock passed in the constructor.
This allows to use alternative clocks, for instance, frame-based.
In this interactive program the t key can be pressed, held, and released to
go through the ADSR cycle. Try also pressing the t key repeatedly and observe
how multiple instances are tracked.
The current ADSR instances are visualized as growing and shrinking circles at the top of the window.
In the center of the window one can see the added value of all current ADSR instances represented as the radius of a white circle.
Demonstrates using ADSRTracker. The core difference
with DemoADSRTracker01 is how shapes are rendered.
Both programs listen to key presses, but the first
program renders tracked shapes inside the extend block,
while this program attaches a unique rendering block
to each tracked shape.
The ADSRTracker maintains a mutable list of trackers,
but they do not have a stable ID. The element with index 3
will have index 2 when elements with lower indices expire.
This is the reason why visualized elements jump left when
an older tracker runs through its complete cycle.
Attaching a function to each triggerOn event allows
rendered shapes to have a stable position on the window.
Notice how the program works with two different triggerIds:
one used when pressing the t key, and the other for the r
key.
This is needed on the triggerOff calls: to tell the tracker
which type of element should wind down. If several items
with that same triggerId exist (when we repeatedly pressed
the same keyboard key), the most recent of them will receive
the event.
