selene tan

I recently needed to make something spiral outwards on a grid. With a bit of experimentation, I found that the steps taken by the spiral always have a pattern like Left Up RightRight DownDown LLL UUU etc. Here’s the snippet I came up with. You can change the starting direction and spiral direction by changing the values in the switch statement.

var currDir:int = 0;
var stepsPerSide:int = 1;
var currSteps:int = 0;
var x:int = startX;
var y:int = startY;

while (notDone())
{
  doThingAt(x, y);

  switch(currDir)
  {
    case 0:
      x += 1;
      break;
    case 1:
      y += 1;
      break;
    case 2:
      x -= 1;
      break;
    case 3:
      y -= 1;
      break;
  }

  currSteps++;
  if (currSteps >= stepsPerSide)
  {
    currDir = (currDir + 1) % 4;
    if (currDir == 0 || currDir == 2)
    {
      ++stepsPerSide;
    }
    currSteps = 0;
  }
}