title: Unity Raycasting does not work with imported object (meshcollider is generated)
body: <p>I have imported a surface which I modeled with 'blender', I imported it with mesh collider. When I want to do a ray casting on this surface to place random objects it won't work. When I set a standard plane above this surface, the ray casting works on this plane. So I think my modeled surface isn't catching the ray casting, but I don't know why. Can anybody help me?</p>
  
  <pre><code>void Start ()
  {
      for(int i = 0; i &lt; numberOfObjects; i++)
      {
          //What we will spawn
          GameObject objectToSpawn = objectsToSpawn[Random.Range(0,objectsToSpawn.Length)];
  
          Vector2 spawnPositionV2 = Random.insideUnitCircle*spawnRadius;
  
          Vector3 spawnPosition = new Vector3(spawnPositionV2.x,0.0f,spawnPositionV2.y);
  
          Vector3 transformOffsetSpawnPosition = transform.position+spawnPosition;
  
          RaycastHit hit;
  
          if (Physics.Raycast (transformOffsetSpawnPosition, Vector3.down, out hit)) {
  
              Vector3 finalSpanPosition = hit.point;
              Instantiate (objectToSpawn, finalSpanPosition, Quaternion.identity);
  
          }
      }
  }
  </code></pre>
  
  <p>}</p>