wolkd/lib/animate.js

Server and user interface to control WS2801 RGB LED strips via SPI

module.exports = function(config, mapping, screen, patterns, modifiers) {
  var bpm = config.bpm;
  var framesPerBeat = config.framesPerBeat;
  var beatMs = 60 / bpm * 1000;
  var msPerFrame = beatMs / framesPerBeat;

  var t = 0;
  var beat = 0;
  var firstMs = new Date().getTime();

  function pixelColor(i) {
    var coordinates = mapping[i];

    var frames = Object.keys(patterns)
      .map(function(name) {
        return patterns[name];
      })
      .filter(function(animation) {
        return animation.value;
      })
      .map(function(pattern) {
        var rgb;
        if (pattern.getPixel) {
          rgb = pattern.getPixel(beat, t, i, coordinates[0], coordinates[1]);
        } else if (pattern.frames) {
          // either t or beat, depending on continuous/perBeat
          var frame = t % pattern.frames.length;
          rgb = pattern.frames[frame][i];
        } else {
          rgb = [0, 0, 0];
        }

        return [
          Math.round(rgb[0] * pattern.value),
          Math.round(rgb[1] * pattern.value),
          Math.round(rgb[2] * pattern.value)
        ];
      });

    if (frames.length) {
      var rgb = frames.reduce(function(rgb1, rgb2) {
        return [
          Math.min(rgb1[0] + rgb2[0], 255),
          Math.min(rgb1[1] + rgb2[1], 255),
          Math.min(rgb1[2] + rgb2[2], 255)
        ];
      });

      Object.keys(modifiers)
        .map(function(name) {
          return modifiers[name];
        })
        .filter(function(modifier) {
          return modifier.value;
        }).forEach(function(modifier) {
          if (modifier.type === 'rgb') {
            rgb = modifier.getPixel(rgb, modifier.value, modifier.data);
          } else if (modifier.type === 'position') {
            rgb = modifier.getPixel(beat, t, i, coordinates[0], coordinates[1], rgb, modifier.value, modifier.data);
          }
        });

      return rgb;
    } else {
      return [0, 0, 0];
    }
  }

  function frame() {
    var currentMs = new Date().getTime();

    for (var i = 0; i < config.pixels && i < mapping.length; i++) {
      var rgb = pixelColor(i);
      screen.setPixel(i, rgb);
    }

    screen.update();

    var timeout = -1;
    while (timeout < 0) {
      timeout = ((t + 1) * msPerFrame + firstMs) - currentMs;
      t += 1;
    }

    beat = Math.floor(t / framesPerBeat);

    setTimeout(frame, timeout);
  }

  frame();

  return {
    setPattern: function(name, value) {
      patterns[name].value = value;
    },

    setModifier: function(name, value, data) {
      modifiers[name].value = value;
      modifiers[name].data = data;
    },

    setBpm: function(bpm, startMs) {
      var beatMs = 60 / bpm * 1000;

      t = 0;
      beat = 0;
      msPerFrame = beatMs / framesPerBeat;
      firstMs = startMs;
    }
  };
};