Dynamo_Arcs.ino

/*
 * Rise and Fall Arc Animation
 */

byte start = 0;
byte end;

Timer arcTimer;
#define ARC_DURATION  500
#define ARC_DELAY     100

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:
  if(arcTimer.isExpired()) {
    // pick a new start
    start = random(6);
    // pick a new end
    end = getAdjacentFace(start);
    arcTimer.set(ARC_DURATION);
  }

  if(!arcTimer.isExpired()) {
    if(arcTimer.getRemaining() > ARC_DELAY) {
      // show start of arc
      byte bri = map(arcTimer.getRemaining(), ARC_DELAY, ARC_DURATION, 0, 255); 
      setColorOnFace(dim(WHITE, bri), start);  
    }
    if(arcTimer.getRemaining() < ARC_DURATION - ARC_DELAY) {
      // show end of arc
      byte bri = map(arcTimer.getRemaining(), 0, ARC_DURATION - ARC_DELAY, 0, 255); 
      setColorOnFace(dim(WHITE, bri), end);  
    }
  }
}

byte getAdjacentFace(byte enter) {
  if(random(2) == 0) {
    return (enter + 1) % 6;
  }
  else {
    return (enter + 6 - 1) % 6;
  }
}