Unity中判断平面上两条线段是否有交点代码参考

        一般的写法参考如下：

bool IsSegmentsIntersect(Vector2 a, Vector2 b, Vector2 c, Vector2 d)
{Vector2 ab = b - a;Vector2 ac = c - a;Vector2 ad = d - a;Vector2 cd = d - c;Vector2 ca = a - c;Vector2 cb = b - c;float crossAB_AC = CrossProduct(ab, ac);float crossAB_AD = CrossProduct(ab, ad);float crossCD_CA = CrossProduct(cd, ca);float crossCD_CB = CrossProduct(cd, cb);// Check general caseif (crossAB_AC * crossAB_AD < 0 && crossCD_CA * crossCD_CB < 0) return true;// Check special cases where points are collinearif (Mathf.Approximately(crossAB_AC, 0) && IsPointOnSegment(c, a, b)) return true;if (Mathf.Approximately(crossAB_AD, 0) && IsPointOnSegment(d, a, b)) return true;if (Mathf.Approximately(crossCD_CA, 0) && IsPointOnSegment(a, c, d)) return true;if (Mathf.Approximately(crossCD_CB, 0) && IsPointOnSegment(b, c, d)) return true;return false;float CrossProduct(Vector2 a, Vector2 b) { return a.x * b.y - a.y * b.x; }bool IsPointOnSegment(Vector2 p, Vector2 a, Vector2 b) { return Mathf.Min(a.x, b.x) <= p.x && p.x <= Mathf.Max(a.x, b.x) && Mathf.Min(a.y, b.y) <= p.y && p.y <= Mathf.Max(a.y, b.y); }
}

        但是有些时候可能我们需要判断大量的线段互相之间是否相交，而且大部分情况是不相交的，我门希望能够快速判断出不相交的结果，这时候需要使用包围盒来提升速度，代码参考如下：

bool IsSegmentsIntersect(Vector2 a, Vector2 b, Vector2 c, Vector2 d)
{if (!BoundingBoxCheck(a, b, c, d)) return false;Vector2 ab = b - a;Vector2 ac = c - a;Vector2 ad = d - a;Vector2 cd = d - c;Vector2 ca = a - c;Vector2 cb = b - c;float crossAB_AC = CrossProduct(ab, ac);float crossAB_AD = CrossProduct(ab, ad);float crossCD_CA = CrossProduct(cd, ca);float crossCD_CB = CrossProduct(cd, cb);if (crossAB_AC * crossAB_AD < 0 && crossCD_CA * crossCD_CB < 0)return true;if (Mathf.Approximately(crossAB_AC, 0) && IsPointOnSegment(c, a, b)) return true;if (Mathf.Approximately(crossAB_AD, 0) && IsPointOnSegment(d, a, b)) return true;if (Mathf.Approximately(crossCD_CA, 0) && IsPointOnSegment(a, c, d)) return true;if (Mathf.Approximately(crossCD_CB, 0) && IsPointOnSegment(b, c, d)) return true;return false;bool BoundingBoxCheck(Vector2 a, Vector2 b, Vector2 c, Vector2 d) { return Mathf.Max(a.x, b.x) >= Mathf.Min(c.x, d.x) && Mathf.Max(c.x, d.x) >= Mathf.Min(a.x, b.x) && Mathf.Max(a.y, b.y) >= Mathf.Min(c.y, d.y) && Mathf.Max(c.y, d.y) >= Mathf.Min(a.y, b.y); }float CrossProduct(Vector2 a, Vector2 b) { return a.x * b.y - a.y * b.x; }bool IsPointOnSegment(Vector2 p, Vector2 a, Vector2 b) { return Mathf.Min(a.x, b.x) <= p.x && p.x <= Mathf.Max(a.x, b.x) && Mathf.Min(a.y, b.y) <= p.y && p.y <= Mathf.Max(a.y, b.y); }
}