Version 4.2.0

include/Asymp.h

@@ -0,0 +1,84 @@
+/***************************************************/
+/*! \class Asymp
+    \brief STK asymptotic curve envelope class
+
+    This class implements a simple envelope generator
+    which asymptotically approaches a target value.
+    The algorithm used is of the form:
+
+    x[n] = a x[n-1] + (1-a) target,
+
+    where a = exp(-T/tau), T is the sample period, and
+    tau is a time constant.  The user can set the time
+    constant (default value = 0.3) and target value.
+    Theoretically, this recursion never reaches its
+    target, though the calculations in this class are
+    stopped when the current value gets within a small
+    threshold value of the target (at which time the
+    current value is set to the target).  It responds
+    to \e keyOn and \e keyOff messages by ramping to
+    1.0 on keyOn and to 0.0 on keyOff.
+
+    by Perry R. Cook and Gary P. Scavone, 1995 - 2004.
+*/
+/***************************************************/
+
+#ifndef STK_ASYMP_H
+#define STK_ASYMP_H
+
+#include "Envelope.h"
+
+const StkFloat TARGET_THRESHOLD = 0.000001;
+
+class Asymp : public Envelope
+{
+ public:
+
+  //! Default constructor.
+  Asymp(void);
+
+  //! Class destructor.
+  ~Asymp(void);
+
+  //! Set target = 1.
+  void keyOn(void);
+
+  //! Set target = 0.
+  void keyOff(void);
+
+  //! Set the asymptotic rate via the time factor \e tau (must be > 0).
+  /*!
+    The rate is computed as described above.  The value of \e tau
+    must be greater than zero.  Values of \e tau close to zero produce
+    fast approach rates, while values greater than 1.0 produce rather
+    slow rates.
+  */
+  void setTau(StkFloat tau);
+
+  //! Set the asymptotic rate based on a time duration (must be > 0).
+  void setTime(StkFloat time);
+
+  //! Set the target value.
+  void setTarget(StkFloat target);
+
+  //! Return one envelope output value.
+  StkFloat tick(void);
+
+  //! Compute \e vectorSize outputs and return them in \e vector.
+  StkFloat *tick( StkFloat *vector, unsigned int vectorSize );
+
+  //! Fill a channel of the StkFrames object with computed outputs.
+  /*!
+    The \c channel argument should be one or greater (the first
+    channel is specified by 1).  An StkError will be thrown if the \c
+    channel argument is zero or it is greater than the number of
+    channels in the StkFrames object.
+  */
+  StkFrames& tick( StkFrames& frames, unsigned int channel = 1 );
+
+ protected:
+  StkFloat factor_;
+  StkFloat constant_;
+};
+
+#endif