Recalculate the bounding volume of the mesh from the vertices.

After modifying vertices you should call this function to ensure the bounding volume is correct. Assigning triangles will automatically Recalculate the bounding volume.

	function Start () {
		var mesh : Mesh = GetComponent(MeshFilter).mesh;
		mesh.RecalculateBounds();
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Start() {
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        mesh.RecalculateBounds();
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Start() as void:
		mesh as Mesh = GetComponent[of MeshFilter]().mesh
		mesh.RecalculateBounds()