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 *       derived from this software without specific prior written permission.
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using System;
using System.Collections.Generic;
using System.Text;

using OpenSim.Framework;
using OpenSim.Region.Framework;
using OpenSim.Region.PhysicsModules.SharedBase;

using Nini.Config;
using log4net;

using OpenMetaverse;

namespace OpenSim.Region.PhysicsModule.BulletS
{
    public sealed class BSTerrainHeightmap : BSTerrainPhys
    {
        static string LogHeader = "[BULLETSIM TERRAIN HEIGHTMAP]";

        BulletHMapInfo m_mapInfo = null;

        // Constructor to build a default, flat heightmap terrain.
        public BSTerrainHeightmap(BSScene physicsScene, Vector3 regionBase, uint id, Vector3 regionSize)
            : base(physicsScene, regionBase, id)
        {
            Vector3 minTerrainCoords = new Vector3(0f, 0f, BSTerrainManager.HEIGHT_INITIALIZATION - BSTerrainManager.HEIGHT_EQUAL_FUDGE);
            Vector3 maxTerrainCoords = new Vector3(regionSize.X, regionSize.Y, BSTerrainManager.HEIGHT_INITIALIZATION);
            int totalHeights = (int)maxTerrainCoords.X * (int)maxTerrainCoords.Y;
            float[] initialMap = new float[totalHeights];
            for (int ii = 0; ii < totalHeights; ii++)
            {
                initialMap[ii] = BSTerrainManager.HEIGHT_INITIALIZATION;
            }
            m_mapInfo = new BulletHMapInfo(id, initialMap, regionSize.X, regionSize.Y);
            m_mapInfo.minCoords = minTerrainCoords;
            m_mapInfo.maxCoords = maxTerrainCoords;
            m_mapInfo.terrainRegionBase = TerrainBase;
            // Don't have to free any previous since we just got here.
            BuildHeightmapTerrain();
        }

        // This minCoords and maxCoords passed in give the size of the terrain (min and max Z
        //         are the high and low points of the heightmap).
        public BSTerrainHeightmap(BSScene physicsScene, Vector3 regionBase, uint id, float[] initialMap,
                                                        Vector3 minCoords, Vector3 maxCoords)
            : base(physicsScene, regionBase, id)
        {
            m_mapInfo = new BulletHMapInfo(id, initialMap, maxCoords.X - minCoords.X, maxCoords.Y - minCoords.Y);
            m_mapInfo.minCoords = minCoords;
            m_mapInfo.maxCoords = maxCoords;
            m_mapInfo.minZ = minCoords.Z;
            m_mapInfo.maxZ = maxCoords.Z;
            m_mapInfo.terrainRegionBase = TerrainBase;

            // Don't have to free any previous since we just got here.
            BuildHeightmapTerrain();
        }

        public override void Dispose()
        {
            ReleaseHeightMapTerrain();
        }

        // Using the information in m_mapInfo, create the physical representation of the heightmap.
        private void BuildHeightmapTerrain()
        {
            // Create the terrain shape from the mapInfo
            m_mapInfo.terrainShape = m_physicsScene.PE.CreateTerrainShape( m_mapInfo.ID,
                                    new Vector3(m_mapInfo.sizeX, m_mapInfo.sizeY, 0), m_mapInfo.minZ, m_mapInfo.maxZ,
                                    m_mapInfo.heightMap, 1f, BSParam.TerrainCollisionMargin);


            // The terrain object initial position is at the center of the object
            Vector3 centerPos;
            centerPos.X = m_mapInfo.minCoords.X + (m_mapInfo.sizeX / 2f);
            centerPos.Y = m_mapInfo.minCoords.Y + (m_mapInfo.sizeY / 2f);
            centerPos.Z = m_mapInfo.minZ + ((m_mapInfo.maxZ - m_mapInfo.minZ) / 2f);

            m_mapInfo.terrainBody = m_physicsScene.PE.CreateBodyWithDefaultMotionState(m_mapInfo.terrainShape,
                                    m_mapInfo.ID, centerPos, Quaternion.Identity);

            // Set current terrain attributes
            m_physicsScene.PE.SetFriction(m_mapInfo.terrainBody, BSParam.TerrainFriction);
            m_physicsScene.PE.SetHitFraction(m_mapInfo.terrainBody, BSParam.TerrainHitFraction);
            m_physicsScene.PE.SetRestitution(m_mapInfo.terrainBody, BSParam.TerrainRestitution);
            m_physicsScene.PE.SetCollisionFlags(m_mapInfo.terrainBody, CollisionFlags.CF_STATIC_OBJECT);

            m_mapInfo.terrainBody.collisionType = CollisionType.Terrain;

            // Return the new terrain to the world of physical objects
            m_physicsScene.PE.AddObjectToWorld(m_physicsScene.World, m_mapInfo.terrainBody);

            // redo its bounding box now that it is in the world
            m_physicsScene.PE.UpdateSingleAabb(m_physicsScene.World, m_mapInfo.terrainBody);

            // Make it so the terrain will not move or be considered for movement.
            m_physicsScene.PE.ForceActivationState(m_mapInfo.terrainBody, ActivationState.DISABLE_SIMULATION);

            return;
        }

        // If there is information in m_mapInfo pointing to physical structures, release same.
        private void ReleaseHeightMapTerrain()
        {
            if (m_mapInfo != null)
            {
                if (m_mapInfo.terrainBody.HasPhysicalBody)
                {
                    m_physicsScene.PE.RemoveObjectFromWorld(m_physicsScene.World, m_mapInfo.terrainBody);
                    // Frees both the body and the shape.
                    m_physicsScene.PE.DestroyObject(m_physicsScene.World, m_mapInfo.terrainBody);
                }
                m_mapInfo.Release();
            }
            m_mapInfo = null;
        }

        // The passed position is relative to the base of the region.
        // There are many assumptions herein that the heightmap increment is 1.
        public override float GetTerrainHeightAtXYZ(Vector3 pos)
        {
            float ret = BSTerrainManager.HEIGHT_GETHEIGHT_RET;

            try {
                int baseX = (int)pos.X;
                int baseY = (int)pos.Y;
                int maxX = (int)m_mapInfo.sizeX;
                int maxY = (int)m_mapInfo.sizeY;
                float diffX = pos.X - (float)baseX;
                float diffY = pos.Y - (float)baseY;

                float mapHeight1 = m_mapInfo.heightMap[baseY * maxY + baseX];
                float mapHeight2 = m_mapInfo.heightMap[Math.Min(baseY + 1, maxY - 1) * maxY + baseX];
                float mapHeight3 = m_mapInfo.heightMap[baseY * maxY + Math.Min(baseX + 1, maxX  - 1)];
                float mapHeight4 = m_mapInfo.heightMap[Math.Min(baseY + 1, maxY - 1) * maxY +  Math.Min(baseX + 1, maxX  - 1)];

                float Xrise = (mapHeight4 - mapHeight3) * diffX;
                float Yrise = (mapHeight2 - mapHeight1) * diffY;

                ret = mapHeight1 + ((Xrise + Yrise) / 2f);
                // m_physicsScene.DetailLog("{0},BSTerrainHeightMap,GetTerrainHeightAtXYZ,pos={1},{2}/{3}/{4}/{5},ret={6}",
                //         BSScene.DetailLogZero, pos, mapHeight1, mapHeight2, mapHeight3, mapHeight4, ret);
            }
            catch
            {
                // Sometimes they give us wonky values of X and Y. Give a warning and return something.
                m_physicsScene.Logger.WarnFormat("{0} Bad request for terrain height. terrainBase={1}, pos={2}",
                                    LogHeader, m_mapInfo.terrainRegionBase, pos);
                ret = BSTerrainManager.HEIGHT_GETHEIGHT_RET;
            }
            return ret;
        }

        // The passed position is relative to the base of the region.
        public override float GetWaterLevelAtXYZ(Vector3 pos)
        {
            return m_physicsScene.SimpleWaterLevel;
        }
    }
}
