複雑な形状のmeshcollider向けのraycast。posListに概ね全部の接触の接触が入ってる。

MultiHitRay.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

[ExecuteInEditMode]
public class MultiHitRay : MonoBehaviour
{
	[Range(0.1f, 30f)]
	public float Length = 20;
	public LayerMask Mask;
	private List<Vector3> posList = new List<Vector3> ();
	int rayCount = 0;
	
	void Update ()
	{
		rayCount = 0;
		
		posList.Clear ();
		
		//  双方向Rayで大雑把な形状を取得
		RaycastHit[] foward = Physics.RaycastAll (transform.position, transform.forward, Length, Mask);
		RaycastHit[] back = Physics.RaycastAll (transform.position + transform.forward * Length, transform.forward * -1, Length, Mask);
		
		rayCount += 2;
		
		// 外枠のポイント一覧を登録
		foreach (RaycastHit hit in foward) {
			posList.Add (hit.point);
		}
		foreach (RaycastHit hit in  back) {
			posList.Add (hit.point);
		}
		
		// 内部のコライダーを取得
		foreach (RaycastHit hit in foward) {
			foreach (RaycastHit hit2 in  back) {
				if (hit.collider == hit2.collider) {

					float maxDistance = Vector3.Distance (hit.point, hit2.point);
			
					// 正方向の外枠から逆方向の外枠までをチェック
					{
						RaycastHit inMeshHit;
						float distance = maxDistance;
						Vector3 currentPoint = hit.point;
						while (hit.collider.Raycast (new Ray (currentPoint + transform.forward, transform.forward), out inMeshHit, distance)) {
							posList.Add (inMeshHit.point);
							currentPoint = inMeshHit.point;
							distance -= inMeshHit.distance;

							rayCount ++;
						}
					}
					
					// 逆方向の外枠から正方向の外枠までをチェック
					{
						RaycastHit inMeshHit;
						float distance = maxDistance;
						Vector3 currentPoint = hit2.point;
						while (hit.collider.Raycast (new Ray (currentPoint - transform.forward, transform.forward * -1), out inMeshHit, distance)) {
							posList.Add (inMeshHit.point);
							currentPoint = inMeshHit.point;
							distance -= inMeshHit.distance;

							rayCount ++;
						}
					}
				}
			}	
		}
	}
	
	void OnGUI ()
	{
		GUILayout.Label (string.Format ("point count{0} raycount:{1}", posList.Count, rayCount));
	}

	void OnDrawGizmos ()
	{
		if (posList == null) {
			return;
		}
		Gizmos.color = Color.white;
		Gizmos.DrawSphere (transform.position, 0.1f);
		Gizmos.DrawSphere (transform.position + transform.forward * Length, 0.1f);
		Gizmos.DrawLine (transform.position, transform.position + transform.forward * Length);
		Gizmos.color = Color.red;
		foreach (Vector3 pos in posList) {
			Gizmos.DrawSphere (pos, 0.1f);
		}
		Gizmos.color = Color.white;
	}
}