包含多边形点的数组。我们可以遍历它的边界吗？

Question

假设我们有一个由点 (x,y)(tile) 填充的数组，所有这些都是伪代码，形成一个封闭且填充的二维多边形。我们如何才能仅遍历构成多边形边界的点？

Answer 1

应用 gift-wrapping algorithm 也称为 Jarvis 行进，它将仅输出构成边界的那些点。

jarvis(S)

    // S is the set of points
    pointOnHull = leftmost point in S // which is guaranteed to be part of the CH(S)

   i = 0
   repeat
      P[i] = pointOnHull
      endpoint = S[0]      // initial endpoint for a candidate edge on the hull
      for j from 1 to |S|
         if (endpoint == pointOnHull) or (S[j] is on left of line from P[i] to endpoint)
            endpoint = S[j]   // found greater left turn, update endpoint
      i = i+1
      pointOnHull = endpoint
   until endpoint == P[0]      // wrapped around to first hull point

包含多边形点的数组。我们可以遍历它的边界吗？

Array that contains points of polygon. Can we iterate through it's border?

arrays

pseudocode