从两条有趣的线，创建盒子并获得所有 4 个角

Question

我有两条线相交，我怎样才能在线上放一个盒子来获得 4 个角坐标。

这张图很好的解释了问题。红色虚线（框）只是虚幻的，目的是得到框的 4（？？？？）个角。

可以按方向或形状绘制线条。

我得到了直线的交点和两条直线的中点。

Answer 1

据我了解，您想要一个 world-XY 对齐的 边界矩形。 不然就不是4个而是8个角了;)

实际上，这些线是否相交并不重要。

简单

• 得到直线的四个给定起点和终点
• 根据这些计算 X 轴和 Y 轴的最小值和最大值
• 根据这些最小和最大排列，您可以得到四个角

例如

// The given line points
Vector2 startA;
Vector2 endA;
Vector2 startB;
Vector2 endB;

// calculate min/max for each axis
var minX = Mathf.Min(startA.x, endA.x, startB.x, endB.x);
var maxX = Mathf.Max(startA.x, endA.x, startB.x, endB.x);
var minY = Mathf.Min(startA.y, endA.y, startB.y, endB.y);
var maxY = Mathf.Max(startA.y, endA.y, startB.y, endB.y);

// permutations of these give you the corners
var topRight = new Vector2(maxX, maxY);
var bottomRight = new Vector2(maxX, minY);
var bottomLeft = new Vector2 (minX, minY);
var topLeft = new Vector2 (minX, maxY);

如果你还需要 Z 轴（为了实际得到一个 box），那么 minZ 和 maxZ 相应地只有四个排列.

// The given line points
Vector3 startA;
Vector3 endA;
Vector3 startB;
Vector3 endB;

// calculate min/max for each axis
var minX = Mathf.Min(startA.x, endA.x, startB.x, endB.x);
var maxX = Mathf.Max(startA.x, endA.x, startB.x, endB.x);
var minY = Mathf.Min(startA.y, endA.y, startB.y, endB.y);
var maxY = Mathf.Max(startA.y, endA.y, startB.y, endB.y);
var minZ = Mathf.Min(startA.z, endA.z, startB.z, endB.z);
var maxZ = Mathf.Max(startA.z, endA.z, startB.z, endB.z);

// permutations of these give you the corners
var topRightFront = new Vector3(maxX, maxY, minZ);
var bottomRightFront = new Vector3(maxX, minY, minZ);
var bottomLeftFront = new Vector3 (minX, minY, minZ);
var topLeftFront = new Vector3 (minX, maxY, minZ);
var topRightBack = new Vector3(maxX, maxY, maxZ);
var bottomRightBack = new Vector3(maxX, minY, maxZ);
var bottomLeftBack = new Vector3 (minX, minY, maxZ);
var topLeftBack = new Vector3 (minX, maxY, maxZ);

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所以前面提到的代码假设您希望 rect/box 与世界轴对齐。

如果不是这种情况，您可以使用以下方式

• 有一个空的 GameObject 作为旋转世界的参考（例如通过 QR 码跟踪等对齐）- 我们称它为“WorldAnchor”
• 将线点转换成那个WorldAnchor
的本地space
• 现在在本地space
对所有轴执行相同的min/max计算
• 做同样的排列得到角
• 最终将角落转换回世界space

类似

// The given line points in WORLD Space
Vector3 startA;
Vector3 endA;
Vector3 startB;
Vector3 endB;

// The given oriented world anchor
Transform anchor;

// The line points converted to LOCAL space
var localStartA = anchor.InverseTransformPoint(startA);
var localEndA = anchor.InverseTransformPoint(endA);
var localStartB = anchor.InverseTransformPoint(startB);
var localEndB = anchor.InverseTransformPoint(endB);

// calculate min/max for each axis
var localMinX = Mathf.Min(localStartA.x, localEndA.x, localStartB.x, localEndB.x);
var localMaxX = Mathf.Max(localStartA.x, localEndA.x, localStartB.x, localEndB.x);
var localMinY = Mathf.Min(localStartA.y, localEndA.y, localStartB.y, localEndB.y);
var localMaxY = Mathf.Max(localStartA.y, localEndA.y, localStartB.y, localEndB.y);
var localMinZ = Mathf.Min(localStartA.z, localEndA.z, localStartB.z, localEndB.z);
var localMaxZ = Mathf.Max(localStartA.z, localEndA.z, localStartB.z, localEndB.z);

// permutations of these give you the corners
var localTopRightFront = new Vector3(localMaxX, localMaxY, localMinZ);
var localBottomRightFront = new Vector3(localMaxX, localMinY, localMinZ);
var localBottomLeftFront = new Vector3 (localMinX, localMinY, localMinZ);
var localTopLeftFront = new Vector3 (localMinX, localMaxY, localMinZ);
var localTopRightBack = new Vector3(localMaxX, localMaxY, localMaxZ);
var localBottomRightBack = new Vector3(localMaxX, localMinY, localMaxZ);
var localBottomLeftBack = new Vector3 (localMinX, localMinY, localMaxZ);
var localTopLeftBack = new Vector3 (localMinX, localMaxY, localMaxZ);

现在要么简单地将角可视化器放置在这些位置，但作为 WorldAnchor 对象的子对象。

或者使用

将它们转换回全局世界space

var topRightFront = anchor.TransformPoint(localTopRightFront);
var bottomRightFront = anchor.TransformPoint(localBottomRightFront);
var bottomLeftFront = anchor.TransformPoint(localBottomLeftFront);
var topLeftFront = anchor.TransformPoint(localTopLeftFront);
var topRightBack = anchor.TransformPoint(localTopRightBack);
var bottomRightBack = anchor.TransformPoint(localBottomRightBack);
var bottomLeftBack = anchor.TransformPoint(localBottomLeftBack);
var topLeftBack = anchor.TransformPoint(localTopLeftBack);