docs: function(sin, cos, step, shiftX, shiftY, dist, offset) {
      var dx = (cos < 0) ? shiftX : 0;
      var dy = (sin < 0) ? shiftY : 0;
  
      step.type = this.check(step.x - dx, step.y - dy);
      step.height = (step.type) > 0 ? 1 : 0;
      step.dist = dist + Math.sqrt(step.len2);
  
      if (shiftX) {
        step.shading = (cos < 0) ? 2 : 0;
      } else {
        step.shading = (sin < 0) ? 2 : 1;
      }
  
      step.offset = offset - Math.floor(offset);
  
      return step;
    }