RaycastHit.barycentricCoordinate

설명

The barycentric coordinate of the triangle we hit.

This lets you interpolate any of the vertex data along the 3 axes.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Update() {
        RaycastHit hit;
        if (!Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit))
            return;
        
        MeshCollider meshCollider = hit.collider as MeshCollider;
        if (meshCollider == null || meshCollider.sharedMesh == null)
            return;
        
        Mesh mesh = meshCollider.sharedMesh;
        Vector3[] normals = mesh.normals;
        int[] triangles = mesh.triangles;
        Vector3 n0 = normals[triangles[hit.triangleIndex * 3 + 0]];
        Vector3 n1 = normals[triangles[hit.triangleIndex * 3 + 1]];
        Vector3 n2 = normals[triangles[hit.triangleIndex * 3 + 2]];
        Vector3 baryCenter = hit.barycentricCoordinate;
        Vector3 interpolatedNormal = n0 * baryCenter.x + n1 * baryCenter.y + n2 * baryCenter.z;
        interpolatedNormal = interpolatedNormal.normalized;
        Transform hitTransform = hit.collider.transform;
        interpolatedNormal = hitTransform.TransformDirection(interpolatedNormal);
        Debug.DrawRay(hit.point, interpolatedNormal);
    }
}