​

const [screen_width, screen_height] = [1024, 512];

const [env_idle, env_attack, env_decay, env_sustain, env_release] = [0,1,2,3,4];

​

let drawing = false;

let timestep = 0;

let lastY = 0;

SCALE_FACTOR = Math.pow(2, 31);//12;

MAX = SCALE_FACTOR - 1;

​

function setup() {

    createCanvas(screen_width, screen_height);

    background(220); //grey

    sampRate = 4096;

    setAttackRate(sampRate);  // .1 second

    setDecayRate(02 * sampRate);

    setReleaseRate(5 * sampRate);

    setSustainLevel(0.6);

  //attackCoef = Math.round(attackCoef * SCALE_FACTOR);

  //attackBase = Math.round(attackBase * SCALE_FACTOR);

  state = 0;

  console.log({ attackRate, decayRate, releaseRate, attackCoef, decayCoef, releaseCoef,   targetRatioA,  targetRatioDR,  attackBase,  decayBase,  releaseBase });

  console.log('attackCoef', attackCoef);

  console.log('attackBase', attackBase);

}

​

function mousePressed() { //gate start

    if (!drawing) background(220);

    drawing = true;

    state = env_attack;

}

​

function mouseReleased() { //gate end

    state = env_release;

}

​

function keyTyped() {

    if (key == 't' && mouseIsPressed) {

        state = env_attack;

    }

}

​

function draw() {

    if (!drawing) return;

​

    for (i = timestep; i < (timestep + 4); i++) {

      for (j = 0; j < 32; j++) {

        process();

      }

        expo = output / SCALE_FACTOR;

        stroke(0); //black line

        strokeWeight(1);

        line(i - 1, (1 - lastY) * screen_height, i, (1 - expo) * screen_height);

        lastY = expo;

    }

​

    timestep = i;

​

    if (timestep >= screen_width) { //stop drawing when we hit the right edge

        timestep = 0;

        drawing = false;

        expo = 0;

    }

}

​

let state;

let output = 0;

let attackRate, decayRate, releaseRate

let attackCoef, decayCoef, releaseCoef;

let sustainLevel;

let targetRatioA = .05, targetRatioDR = .001;

let attackBase, decayBase, releaseBase;

​

let count = 0;

​

function process() {

  count++;

    switch (state) {

        case env_idle:

            break;

        case env_attack:

          output = (output * attackCoef) / SCALE_FACTOR + attackBase;  

          output = Math.round(output);

          //output = (output * attackCoef) + attackBase;

            if (output >= MAX) {

              console.log({ count });

               count = 0;

                output = MAX;

                state = env_decay;

            }

            break;

        case env_decay:

            //output = (output * decayCoef) + decayBase;

          output = (output * Math.round(decayCoef * SCALE_FACTOR)) / SCALE_FACTOR + Math.round(decayBase * SCALE_FACTOR);  

          output = Math.round(output);

            if (output <= sustainLevel * SCALE_FACTOR) {

                output = sustainLevel * SCALE_FACTOR;

                state = env_sustain;

            }

            break;

        case env_sustain:

            break;

        case env_release:

            output = releaseBase + output * releaseCoef;

            if (output <= 0.0) {

                output = 0.0;

                state = env_idle;

            }

    }

    return output;

}

​

function setAttackRate(rate) {

    attackRate = rate;

    attackCoef = calcCoef(rate, targetRatioA);

    attackCoef = Math.round(attackCoef * SCALE_FACTOR);

    attackBase = ((MAX + Math.round(targetRatioA * SCALE_FACTOR)) * (MAX - attackCoef)) / SCALE_FACTOR;

    attackBase = Math.round(attackBase);

}

​

function setDecayRate(rate) {

    decayRate = rate;

    decayCoef = calcCoef(rate, targetRatioDR);

    decayBase = (sustainLevel - targetRatioDR) * (1.0 - decayCoef);

}

​

function setReleaseRate(rate) {

    releaseRate = rate;

    releaseCoef = calcCoef(rate, targetRatioDR);

    releaseBase = -targetRatioDR * (1.0 - releaseCoef);

}

​

function calcCoef(rate, targetRatio) {

    return (rate <= 0) ? 0.0 : Math.exp(-Math.log((1.0 + targetRatio) / targetRatio) / rate);

  //return (rate <= 0) ? 0.0 : Math.pow((1.0 + targetRatio) / targetRatio, -1 / rate);

}

​

function setSustainLevel(level) {

    sustainLevel = level;

    decayBase = (sustainLevel - targetRatioDR) * (1.0 - decayCoef);

}

​