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Src/Unity/Scripts/Physics/GeometryUtils.cs

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace BITKit.Physics
+{
+    public static class GeometryUtils
+    {
+        /// <summary>
+        /// 获取一个点到一条线段的最近点
+        /// </summary>
+        /// <param name="point"></param>
+        /// <param name="lineStart"></param>
+        /// <param name="lineEnd"></param>
+        /// <returns></returns>
+        public static Vector3 PointToLineSegmentDistance(Vector3 point, Vector3 lineStart, Vector3 lineEnd)
+        {
+            Vector3 lineDirection = lineEnd - lineStart;
+            Vector3 pointDirection = point - lineStart;
+ 
+            float lineLength = lineDirection.magnitude;
+            lineDirection.Normalize();
+ 
+            float dotProduct = Vector3.Dot(pointDirection, lineDirection);
+            dotProduct = Mathf.Clamp(dotProduct, 0f, lineLength);
+ 
+            Vector3 closestPoint = lineStart + lineDirection * dotProduct;
+            return closestPoint;
+        }
+        /// <summary>
+        /// 获取一个点到一个三角形内最短距离的点
+        /// </summary>
+        /// <param name="a">三角形顶点a</param>
+        /// <param name="b">三角形顶点b</param>
+        /// <param name="c">三角形顶点c</param>
+        /// <param name="pos"></param>
+        /// <returns></returns>
+        public static Vector3 GetPosInTriangle(Vector3 a, Vector3 b, Vector3 c, Vector3 pos)
+        {
+            Vector3 normal = Vector3.Cross(b - a, c - a).normalized;
+            Vector3 toPoint = pos - a;
+            float distance = Vector3.Dot(toPoint, normal);
+ 
+            Vector3 targetPos = pos - distance * normal;
+ 
+            if(PointInTriangle(targetPos, a, b, c))
+                return targetPos;
+            else
+            {
+                Vector3 p1 = PointToLineSegmentDistance(pos, a, b);
+                Vector3 p2 = PointToLineSegmentDistance(pos, a, c);
+                Vector3 p3 = PointToLineSegmentDistance(pos, b, c);
+ 
+                float d1 = Vector3.Distance(p1, pos);
+                float d2 = Vector3.Distance(p2, pos);
+                float d3 = Vector3.Distance(p3, pos);
+ 
+                if (d1 <= d2 && d1 <= d3)
+                    return p1;
+                else if (d2 <= d3 && d2 <= d1)
+                    return p2;
+                else /*if(d3 <= d1 && d3 <= d2)*/
+                    return p3;
+ 
+                //return default;
+            }
+        }
+ 
+        /// <summary>
+        /// 判断一个点是否在三角形内
+        /// </summary>
+        /// <param name="pos"></param>
+        /// <param name="a"></param>
+        /// <param name="b"></param>
+        /// <param name="c"></param>
+        /// <returns></returns>
+        public static bool PointInTriangle(Vector3 pos, Vector3 a, Vector3 b, Vector3 c)
+        {
+            var v0 = c - a;
+            var v1 = b - a;
+            var v2 = pos - a;
+ 
+            var dot00 = Vector3.Dot(v0, v0);
+            var dot01 = Vector3.Dot(v0, v1);
+            var dot02 = Vector3.Dot(v0, v2);
+            var dot11 = Vector3.Dot(v1, v1);
+            var dot12 = Vector3.Dot(v1, v2);
+ 
+            var invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
+            var u = (dot11 * dot02 - dot01 * dot12) * invDenom;
+            var v = (dot00 * dot12 - dot01 * dot02) * invDenom;
+ 
+            // 如果u和v都在[0,1]的范围内，那么点P在三角形ABC内
+            return (u >= 0) && (v >= 0) && (u + v < 1);
+        }
+    }
+
+}
+