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Assets/Pixel3D/Scripts/MeshSurfaceSampler.cs

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+using System.Collections.Generic;
+using UnityEngine;
+
+public class MeshSurfaceSampler : MonoBehaviour
+{
+
+    [SerializeField] float _density = 1;
+    [SerializeField] int seed = 42;
+
+    Mesh _mesh;
+
+    [HideInInspector] public Vector3[] points;
+    [HideInInspector] public Vector3[] normals;
+
+    void OnEnable()
+    {
+        _mesh = GetComponent<MeshFilter>().mesh;
+        GeneratePoints();
+    }
+
+    public void GeneratePoints()
+    {
+        Random.InitState(seed);
+
+        var tris = _mesh.triangles;
+        var triangleAreas = new float[tris.Length / 3];
+
+        var totalArea = 0.0f;
+        for (var i = 0; i < tris.Length; i += 3)
+        {
+            var v1 = _mesh.vertices[tris[i]];
+            var v2 = _mesh.vertices[tris[i + 1]];
+            var v3 = _mesh.vertices[tris[i + 2]];
+            var area = TriangleArea(v1, v2, v3);
+            totalArea += area;
+            triangleAreas[i / 3] = area;
+        }
+
+        var pointList = new List<Vector3>();
+        var normalList = new List<Vector3>();
+
+        var totalPoints = Mathf.CeilToInt(totalArea * _density);
+        for (var i = 0; i < triangleAreas.Length; i++)
+        {
+            var pointsInThisTriangle = Mathf.CeilToInt(triangleAreas[i] / totalArea * totalPoints);
+            for (var j = 0; j < pointsInThisTriangle; j++)
+            {
+                (Vector3 point, Vector3 normal) = RandomPointAndNormalInTriangle(
+                    _mesh.vertices[tris[i * 3]], _mesh.vertices[tris[i * 3 + 1]], _mesh.vertices[tris[i * 3 + 2]],
+                    _mesh.normals[tris[i * 3]], _mesh.normals[tris[i * 3 + 1]], _mesh.normals[tris[i * 3 + 2]]);
+
+                pointList.Add(transform.TransformPoint(point));
+                // normalList.Add(normal);
+                normalList.Add(transform.TransformDirection(normal));
+                // Debug.DrawRay(point, normal, Color.red, 10);
+            }
+        }
+        points = pointList.ToArray();
+        normals = normalList.ToArray();
+    }
+
+    float TriangleArea(Vector3 v1, Vector3 v2, Vector3 v3)
+    {
+        return Vector3.Cross(v1 - v2, v1 - v3).magnitude * 0.5f;
+    }
+
+    (Vector3, Vector3) RandomPointAndNormalInTriangle(Vector3 v1, Vector3 v2, Vector3 v3, Vector3 n1, Vector3 n2, Vector3 n3)
+    {
+        var r1 = Mathf.Sqrt(Random.value);
+        var r2 = Random.value;
+        var point = (1 - r1) * v1 + r1 * (1 - r2) * v2 + r1 * r2 * v3;
+        var normal = ((1 - r1) * n1 + r1 * (1 - r2) * n2 + r1 * r2 * n3).normalized;
+        return (point, normal);
+    }
+
+    public bool ArePointsGenerated()
+    {
+        return points != null && points.Length > 0;
+    }
+}