rebound.lua

-- rebound: a kinetic sequencer
--
-- key1: shift^
-- key2: add/^remove orb
-- key3: select next orb
-- enc1: change orb note
-- enc2: rotate orb^s
-- enc3: accelerate orb^s

-- written by nf in august 2018
-- params and scales taken from tehn/awake, thanks

local cs = require 'controlspec'

engine.name = "PolyPerc"

local balls = {}
local cur_ball = 0

local scale_degrees = {2,1,2,2,2,1,2}
local notes = {}
local freqs = {}

local BeatClock = require 'beatclock'
local clk = BeatClock.new()

local freq_queue = {}

local shift = false

function init()
  screen.aa(1)

  local u = metro.alloc()
  u.time = 1/60
  u.count = -1
  u.callback = update
  u:start()

  clk.on_step = play_notes
  clk.on_select_internal = function() clk:start() end
  clk:add_clock_params()

  params:add_separator()

  params:add_number("scale mode",1,7,3)
  params:set_action("scale mode", function(n) 
    build_scale()
  end) 
  params:add_number("trans",-12,24,0)
  params:set_action("trans", function(n) 
    build_scale()
  end)

  params:add_separator()

  cs.AMP = cs.new(0,1,'lin',0,0.5,'')
  params:add_control("amp",cs.AMP)
  params:set_action("amp",
  function(x) engine.amp(x) end) 

  cs.PW = cs.new(0,100,'lin',0,80,'%')
  params:add_control("pw",cs.PW)
  params:set_action("pw",
  function(x) engine.pw(x/100) end) 

  cs.REL = cs.new(0.1,3.2,'lin',0,0.2,'s') 
  params:add_control("release",cs.REL)
  params:set_action("release",
  function(x) engine.release(x) end) 

  cs.CUT = cs.new(50,5000,'exp',0,555,'hz')
  params:add_control("cutoff",cs.CUT)
  params:set_action("cutoff",
  function(x) engine.cutoff(x) end) 

  cs.GAIN = cs.new(0,4,'lin',0,1,'')
  params:add_control("gain",cs.GAIN)
  params:set_action("gain",
  function(x) engine.gain(x) end) 

  params:bang()
end

function build_scale()
  local scale = params:get("scale mode")
  local trans = params:get("trans")
  local n = 0
  for i=1,32 do
    notes[i] = n
    n = n + scale_degrees[(scale + i)%#scale_degrees + 1]
  end
  for i=1,#notes do
    freqs[i] = 55*2^((notes[i]+trans)/12)
  end
end 

function redraw()
  screen.clear()
  if shift then
    screen.level(5)
    screen.line_width(1)
    screen.rect(1,1,126,62)
    screen.stroke()
  end
  for i=1,#balls do
    drawball(balls[i], i == cur_ball)
  end
  screen.update()
end

function update()
  for i=1,#balls do
    updateball(balls[i])
  end
  redraw()
end

function enc(n, d)
  if n == 1 and not shift and cur_ball > 0 then
    -- note
    balls[cur_ball].n = math.min(math.max(balls[cur_ball].n+d, 1), #notes)
  elseif n == 2 then
    -- rotate
    for i=1,#balls do
      if shift or i == cur_ball then
        balls[i].a = balls[i].a - d/10
      end
    end
  elseif n == 3 then
    -- accelerate
    for i=1,#balls do
      if shift or i == cur_ball then
        balls[i].v = balls[i].v + d/10
      end
    end
  end
end

function key(n, z)
  if n == 1 then
    -- shift
    shift = z == 1
  elseif n == 2 and z == 1 then
    if shift then
      -- remove ball
      table.remove(balls, cur_ball)
      if cur_ball > #balls then
        cur_ball = #balls
      end
    else
      -- add ball
      table.insert(balls, newball())
      cur_ball = #balls
    end
  elseif n == 3 and z == 1 and not shift and #balls > 0 then
    -- select next ball
    cur_ball = cur_ball%#balls+1
  end
end

function newball()
  return {
    x = 64,
    y = 32,
    v = 0.5*math.random()+0.5,
    a = math.random()*2*math.pi,
    n = math.floor(math.random()*#notes+1),
  }
end

function drawball(b, hilite)
  screen.level(hilite and 15 or 5)
  screen.circle(b.x, b.y, hilite and 2 or 1.5)
  screen.fill()
end

function updateball(b)
  b.x = b.x + math.sin(b.a)*b.v
  b.y = b.y + math.cos(b.a)*b.v

  local minx = 2
  local miny = 2
  local maxx = 126
  local maxy = 62
  if b.x >= maxx then
    b.x = maxx
    b.a = 2*math.pi - b.a
    enqueue_note(b, 0)
  elseif b.x <= minx then
    b.x = minx
    b.a = 2*math.pi - b.a
    enqueue_note(b, 1)
  elseif b.y >= maxy then
    b.y = maxy
    b.a = math.pi - b.a
    enqueue_note(b, 2)
  elseif b.y <= miny then
    b.y = miny
    b.a = math.pi - b.a
    enqueue_note(b, 3)
  end
end

function enqueue_note(b, z)
  local f = freqs[b.n]
  if z == 0 then
    f = f * 2
  elseif z == 1 then
    f = f / 2
  end
  table.insert(freq_queue, f)
end

function play_notes()
  while #freq_queue > 0 do
    engine.hz(table.remove(freq_queue))
  end
end