滑动响应指向 - 广场碰撞

Question

在一般条款和伪代码，这将是有沿墙壁滑动的碰撞响应的最好方式，如果墙面实际上只是一个整个广场的那一个点的一部分正在碰撞？所使用的碰撞测试方法是测试以确定点是否位于正方形中。

我应该把正方形分成四条线，只计算最短的距离，然后将点移回距离？如果是，那我怎样才能确定点后最接近的平方的边缘？

Answer 1

由靠墙测试的移动矢量检测碰撞点。如果你知道你的事情的表面（例如，你说这是一个框部分）你也许可以同时测试多个墙壁。

该溶液可以是2D和3D之间略有不同。因为你说的是​​“正方形”而不是“立方体”或“盒子”，所以我会使用2D。

一旦你知道你的点击中的位置，就可以将剩余的运动矢量与墙壁方向对齐（从另一个点减去墙上的一个点然后标准化），然后按照该方向缩放墙的方向。假设没有摩擦，这是平行于墙的运动量。

编辑添加以下代码：

样板：

import math 

class Vector2d: 
    def __init__(self, x, y): 
     self.x = x 
     self.y = y 

    def __add__(self, rhs): 
     return Vector2d(self.x + rhs.x, self.y + rhs.y) 

    def __sub__(self, rhs): 
     return Vector2d(self.x - rhs.x, self.y - rhs.y) 

    def GetScaled(self, scale): 
     return Vector2d(self.x * scale, self.y * scale) 

    def GetLength(self): 
     return math.sqrt((self.x * self.x) + (self.y * self.y)) 

    def GetNormalized(self): 
     return self.GetScaled(1.0/self.GetLength()) 

def DotProduct(v0, v1): 
    return (v0.x * v1.x) + (v0.y * v1.y) 

真正的业务：

class Wall2d: 
    def init(self, point0, point1): 
     """point0, point1 are Vector2ds""" 
     self.p0 = point0 
     self.p1 = point1 

     # these three steps could be combined to optimize, but 
     # for demonstration are left explicit 
     self.dir = self.p1 - self.p0 
     self.length = self.dir.GetLength() 
     self.dir = self.dir.GetNormalized() 

     # computing the normal in 3D would require three points 
     # on the face and a cross product 
     self.normal = Vector2d(self.length.y, -self.length.x) 

    def LineSegmentCollides(self, pointStart, pointEnd): 
     startDot = DotProduct(pointStart - self.p0, self.normal) 
     endDot = DotProduct(pointEnd - self.p0, self.normal) 
     if startDot * endDot < 0: 
      # the only way a collision can occur is if the start 
      # and end are on opposite sides of the wall, so their 
      # dot product results will have opposite signs, so 
      # the result of the multiplication is negative 
      moveVector = pointEnd - pointStart 

      # scale the movement vector by the ratio of the move 
      # vector on the "start" side versus the total length 
      # of the movement in the axis of the normal 
      collisionDelta = moveVector.GetScaled(startDot/
                (startDot + endDot)) 
      collisionPoint = pointStart + collisionDelta 

      collisionDot = DotProduct(collisionPoint - self.p0, self.dir) 
      if (collisionDot > 0) && (collisionDot < self.length): 
       # we've hit the wall between p0 and p1 (other 
       # values of collisionDot mean we missed on one 
       # end or the other) 

       # now, collision response is up to you. In this 
       # case, we'll just zero out the movement in the 
       # direction of the wall after the collision 
       # (sorry about the poor naming) 
       # note that we don't actually care about the actual 
       # point of collision here. 
       collisionPushBack = moveVector.GetScaled(
             endDot/(startDot + endDot)) 
       endPoint = pointEnd + collisionPushBack 

       return True 
     return False 

我希望这是有益的。