//=============================================================================
  // Terrain.h by Frank Luna (C) 2004 All Rights Reserved.
  //
  // Assumptions: In this book, we only use one terrain per demo and we 
  //              construct the terrain geometry directly in world space.
  //=============================================================================
  
  ifndef TERRAIN_H
  define TERRAIN_H
  
  include <Heightmap.h>
  include <d3dUtil.h>
  include <Vertex.h>
  
   
  class Terrain
  {
  public:
          Terrain(UINT vertRows, UINT vertCols, float dx, float dz, 
                  std::string heightmap, std::string tex0, std::string tex1, 
                  std::string tex2, std::string blendMap, float heightScale, 
                  float yOffset);
          ~Terrain();
  
          DWORD getNumTriangles();
          DWORD getNumVertices();
  
          float getWidth();
          float getDepth();
  
          void onLostDevice();
          void onResetDevice();
  
          // (x, z) relative to terrain's local space.
          float getHeight(float x, float z);
          
          void setDirToSunW(const D3DXVECTOR3& d);
  
          void draw();
  
  private:
          void buildGeometry();
          void buildSubGridMesh(RECT& R, VertexPNT* gridVerts); 
          void buildEffect();
  
          struct SubGrid
          {
                  ID3DXMesh* mesh;
                  AABB box;
  
                  // For sorting.
                  bool operator<(const SubGrid& rhs)const;
  
                  const static int NUM_ROWS  = 33;
                  const static int NUM_COLS  = 33;
                  const static int NUM_TRIS  = (NUM_ROWS-1)*(NUM_COLS-1)*2;
                  const static int NUM_VERTS = NUM_ROWS*NUM_COLS;
          };
  private:
          Heightmap mHeightmap;
          std::vector<SubGrid> mSubGrids;
  
          DWORD mVertRows;
          DWORD mVertCols;
  
          float mWidth;
          float mDepth;
  
          float mDX;
          float mDZ;
  
          IDirect3DTexture9* mTex0;
          IDirect3DTexture9* mTex1;
          IDirect3DTexture9* mTex2;
          IDirect3DTexture9* mBlendMap;
          ID3DXEffect*       mFX;
          D3DXHANDLE         mhTech;
          D3DXHANDLE         mhViewProj;
          D3DXHANDLE         mhDirToSunW;
          D3DXHANDLE         mhTex0;
          D3DXHANDLE         mhTex1;
          D3DXHANDLE         mhTex2;
          D3DXHANDLE         mhBlendMap;
  };
  
  endif // TERRAIN_H