GHZShaPAN/Assets/WorldComposer/Scripts/MultiTerrainBoost.cs

using UnityEngine;
using System.Collections;

namespace WorldComposer
{
    public class MultiTerrainBoost : MonoBehaviour
    {
        Camera MainCamera;
        bool[] active1;
        Terrain[] terrains;
        Bounds[] bounds;
        Plane[] planes;
        float distance;
        int count_terrain;

        void Start()
        {
            MainCamera = GetComponent<Camera>();
            terrains = Resources.FindObjectsOfTypeAll(typeof(Terrain)) as Terrain[];
            bounds = new Bounds[terrains.Length];
            active1 = new bool[terrains.Length];
            calcBounds();
        }

        void LateUpdate()
        {
            calcFrustrum();

            for (count_terrain = 0; count_terrain < bounds.Length; ++count_terrain)
            {
                if (IsRenderedFrom(bounds[count_terrain]))
                {
                    if (!active1[count_terrain])
                    {
                        terrains[count_terrain].enabled = true;
                        active1[count_terrain] = true;
                    }
                }
                else
                {
                    if (active1[count_terrain])
                    {
                        terrains[count_terrain].enabled = false;
                        active1[count_terrain] = false;
                    }
                }
            }
        }

        void calcBounds()
        {
            for (count_terrain = 0; count_terrain < terrains.Length; ++count_terrain)
            {
                bounds[count_terrain].size = terrains[count_terrain].terrainData.size;
                bounds[count_terrain].center = new Vector3(terrains[count_terrain].transform.position.x + (bounds[count_terrain].size.x / 2), terrains[count_terrain].transform.position.y + (bounds[count_terrain].size.y / 2), terrains[count_terrain].transform.position.z + (bounds[count_terrain].size.z / 2));
                active1[count_terrain] = true;
            }
        }

        void calcFrustrum()
        {
            planes = GeometryUtility.CalculateFrustumPlanes(MainCamera);
        }

        bool IsRenderedFrom(Bounds bound)
        {
            return GeometryUtility.TestPlanesAABB(planes, bound);
        }
    }
}