2. Envelopes and Metro

New objects: line~, vline~, metro, random

Review previous patch

• Patcher Elements
  • connections
  • inlets
  • outlets
• Sliders
  • right-click to show properties
• Numbers
  • drag to change in read/perform mode
• Objects
  • inlets and outlets differ depending on object type
  • objects that deal with audio signals get ~ at the end of the name

Help!

• All computer programmers use documentation.
• Two ways to access:
  • Help > Browser
    • start with the folder at the top, called “Pure Data”
  • right-click an object > Help
• All help files are Pd patches!
  • open in perform mode
  • test different inputs/outputs
  • ⌘E to switch to edit mode
  • copy-paste into your patch and edit

Smoothing things out with line~

• Note the noise artifacts from moving the amplitude slider
  • Why do those occur?
  • Answer, the clicks are the result of the computer trying to change the waveform instantly, which creates a vertical jump in an otherwise smooth sine curve.
• Solve artifacts with line~
  • creates a smooth change over time
  • takes a Message as input
    • message formatted with two numbers: the target value, and the amount of time to reach it (in ms)
  • demo: line~ to control volume
    • disconnect volume slider
    • connect new line~ to right inlet of multiplication
    • create a message box that goes to 0.8 over 400ms
    • create a second message box that goes to 0 over 1000ms
  • What’s the problem with this approach to smoothing out our slider behavior?
    • we can’t make enough Messages for the levels of volume we would want.
  • Message variables take input and incorporate them into the output. They’re number with $ in front
  • demo: line~ with message variables to smooth out slider numbers
    • replace 0.6 (or whatever value) with $1
    • discuss second number (something short is good, 50ms or smaller)

Generating an envelope with vline~

• Note that using this slider for setting volume is nice, but it’s not very practical for attacks
• vline~ allows us do the equivalent of stringing several line~ objects together
  • takes a message object like line~
  • uses a comma to separate line segments:
    • first segment is target and time
    • second and later are target, then time, then offest
    • the offset is from the beginning of the vline
  • demo: create a triggerable envelope
    • Add a new *~ element above the final volume slider
    • connect new vline~ to right inlet of new *~
    • connect new Message to vline~ that defines an attact and a release

Automating with metro

• This envelope is cool, but it would be cooler if we didn’t have to click it each time we wanted something to happen!
• Metro is short for metronome and it behaves pretty close to what you might expect
• demo: automate envelope triggering with metro
  • create a metro and connect to vline~’s message
  • give metro a creation argument in ms
  • create a toggle
  • start em up
  • add a number box (or slider) to the right inlet of metro
    • What’s happening here?
    • You’re overriding metro’s default argument with a new input.