[orx-delegate-magic, orx-envelopes] Add orx-delegate-magic, orx-envelopes

orx-envelopes/src/commonMain/kotlin/ADSR.kt

@@ -0,0 +1,37 @@
+package org.openrndr.extra.envelopes
+
+import org.openrndr.math.mix
+import kotlin.math.min
+
+data class ADSR(
+    val attackDuration: Double,
+    val decayDuration: Double,
+    val sustainValue: Double,
+    val releaseDuration: Double
+) : Envelope{
+    override fun value(t: Double, tOff: Double): Double {
+        return adsr(attackDuration, decayDuration, sustainValue, releaseDuration, t, tOff)
+    }
+
+    override fun isActive(t: Double, tOff: Double): Boolean {
+        return !(t - tOff > releaseDuration)
+    }
+}
+
+fun adsr(
+    attackDuration: Double,
+    decayDuration: Double,
+    sustainValue: Double,
+    releaseDuration: Double,
+    t: Double,
+    tOff: Double = 1E10
+): Double {
+
+    val da = t / attackDuration
+    val dc = (t - attackDuration) / decayDuration
+
+    val vOn = mix(min(1.0, da), sustainValue, dc.coerceIn(0.0..1.0))
+
+    return mix(vOn, 0.0, ((t - tOff) / releaseDuration).coerceIn(0.0..1.0))
+
+}