//=============================================================================
  // ShadowDemo.cpp by Frank Luna (C) 2005 All Rights Reserved.
  //
  // Prevents double blending with the stencil buffer.
  //
  // Controls: Use mouse to orbit and zoom; use the 'W' and 'S' keys to 
  //           alter the height of the camera.
  //           Use 'A' and 'D' keys to translate the teapot on the x-axis.
  //=============================================================================
  
  include <d3dApp.h>
  include <DirectInput.h>
  include <crtdbg.h>
  include <GfxStats.h>
  include <list>
  include <Vertex.h>
  
  class ShadowDemo : public D3DApp
  {
  public:
          ShadowDemo(HINSTANCE hInstance, std::string winCaption, D3DDEVTYPE devType, DWORD requestedVP);
          ~ShadowDemo();
  
          bool checkDeviceCaps();
          void onLostDevice();
          void onResetDevice();
          void updateScene(float dt);
          void drawScene();
  
          // Helper methods
          void buildRoomGeometry();
          void buildFX();
          void buildViewMtx();
          void buildProjMtx();
  
          void drawRoom();
          void drawMirror();
          void drawTeapot();
          void drawReflectedTeapot();
          void drawTeapotShadow();
          void genSphericalTexCoords();
  
  private:
          GfxStats* mGfxStats;
          
          IDirect3DVertexBuffer9* mRoomVB;
          ID3DXMesh*              mTeapot;
  
          IDirect3DTexture9*     mFloorTex;
          IDirect3DTexture9*     mWallTex;
          IDirect3DTexture9*     mMirrorTex;
          IDirect3DTexture9*     mTeapotTex;
  
          ID3DXEffect* mFX;
          D3DXHANDLE   mhTech;
          D3DXHANDLE   mhWVP;
          D3DXHANDLE   mhWorldInvTrans;
          D3DXHANDLE   mhLightVecW;
          D3DXHANDLE   mhDiffuseMtrl;
          D3DXHANDLE   mhDiffuseLight;
          D3DXHANDLE   mhAmbientMtrl;
          D3DXHANDLE   mhAmbientLight;
          D3DXHANDLE   mhSpecularMtrl;
          D3DXHANDLE   mhSpecularLight;
          D3DXHANDLE   mhSpecularPower;
          D3DXHANDLE   mhEyePos;
          D3DXHANDLE   mhWorld;
          D3DXHANDLE   mhTex;
  
          Mtrl mWhiteMtrl;
          Mtrl mShadowMtrl;
  
          D3DXVECTOR3 mLightVecW;
          D3DXCOLOR   mAmbientLight;
          D3DXCOLOR   mDiffuseLight;
          D3DXCOLOR   mSpecularLight;
  
          float mCameraRotationY;
          float mCameraRadius;
          float mCameraHeight;
  
          D3DXMATRIX mRoomWorld;
          D3DXMATRIX mTeapotWorld;
  
          D3DXMATRIX mView;
          D3DXMATRIX mProj;
  };
  
  int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE prevInstance,
                                     PSTR cmdLine, int showCmd)
  {
          // Enable run-time memory check for debug builds.
          #if defined(DEBUG) | defined(_DEBUG)
                  _CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
          #endif
  
          ShadowDemo app(hInstance, "Shadow Demo", D3DDEVTYPE_HAL, D3DCREATE_HARDWARE_VERTEXPROCESSING);
          gd3dApp = &app;
  
          DirectInput di(DISCL_NONEXCLUSIVE|DISCL_FOREGROUND, DISCL_NONEXCLUSIVE|DISCL_FOREGROUND);
          gDInput = &di;
  
      return gd3dApp->run();
  }
  
  ShadowDemo::ShadowDemo(HINSTANCE hInstance, std::string winCaption, D3DDEVTYPE devType, DWORD requestedVP)
  : D3DApp(hInstance, winCaption, devType, requestedVP)
  {
          if(!checkDeviceCaps())
          {
                  MessageBox(0, "checkDeviceCaps() Failed", 0, 0);
                  PostQuitMessage(0);
          }
  
          InitAllVertexDeclarations();
  
          mGfxStats = new GfxStats();
          
  
          mCameraRadius    = 15.0f;
          mCameraRotationY = 1.4f * D3DX_PI;
          mCameraHeight    = 5.0f;
  
          mLightVecW     = D3DXVECTOR3(-0.577f, 0.577f, -0.577f);
          mDiffuseLight  = D3DXCOLOR(1.0f, 1.0f, 1.0f, 1.0f);
          mAmbientLight  = D3DXCOLOR(0.6f, 0.6f, 0.6f, 1.0f);
          mSpecularLight = D3DXCOLOR(1.0f, 1.0f, 1.0f, 1.0f);
  
          mWhiteMtrl.ambient   = WHITE;
          mWhiteMtrl.diffuse   = WHITE;
          mWhiteMtrl.spec      = WHITE * 0.8f;
          mWhiteMtrl.specPower = 16.0f;
  
          mShadowMtrl.ambient   = BLACK;
          mShadowMtrl.diffuse   = BLACK;
          mShadowMtrl.diffuse.a = 0.5f; // 50% transparent.
          mShadowMtrl.spec      = BLACK;
          mShadowMtrl.specPower = 1.0f;
  
          D3DXMatrixIdentity(&mRoomWorld);
          D3DXMatrixTranslation(&mTeapotWorld, 0.0f, 3.0f, -6.0f);
  
          HR(D3DXCreateTextureFromFile(gd3dDevice, "checkboard.dds", &mFloorTex));
          HR(D3DXCreateTextureFromFile(gd3dDevice, "brick2.dds", &mWallTex));
          HR(D3DXCreateTextureFromFile(gd3dDevice, "ice.dds", &mMirrorTex));
          HR(D3DXCreateTextureFromFile(gd3dDevice, "brick1.dds", &mTeapotTex));
  
          HR(D3DXCreateTeapot(gd3dDevice, &mTeapot, 0));
          // Generate texture coordinates for the teapot.
          genSphericalTexCoords();
  
          // Room geometry count.
          mGfxStats->addVertices(24);
          mGfxStats->addTriangles(8);
  
          // We draw the teapot 3 times--one regularly, one reflected and one shadowed.
          mGfxStats->addVertices(mTeapot->GetNumVertices() * 3);
          mGfxStats->addTriangles(mTeapot->GetNumFaces()   * 3);
  
          buildRoomGeometry();
          buildFX();
  
          onResetDevice();
  }
  
  ShadowDemo::~ShadowDemo()
  {
          delete mGfxStats;
          ReleaseCOM(mRoomVB);
          ReleaseCOM(mTeapot);
          ReleaseCOM(mFloorTex);
          ReleaseCOM(mWallTex);
          ReleaseCOM(mMirrorTex);
          ReleaseCOM(mTeapotTex);
          ReleaseCOM(mFX);
  
          DestroyAllVertexDeclarations();
  }
  
  bool ShadowDemo::checkDeviceCaps()
  {
          D3DCAPS9 caps;
          HR(gd3dDevice->GetDeviceCaps(&caps));
  
          // Check for vertex shader version 2.0 support.
          if( caps.VertexShaderVersion < D3DVS_VERSION(2, 0) )
                  return false;
  
          // Check for pixel shader version 2.0 support.
          if( caps.PixelShaderVersion < D3DPS_VERSION(2, 0) )
                  return false;
  
          return true;
  }
  
  void ShadowDemo::onLostDevice()
  {
          mGfxStats->onLostDevice();
          HR(mFX->OnLostDevice());
  }
  
  void ShadowDemo::onResetDevice()
  {
          mGfxStats->onResetDevice();
          HR(mFX->OnResetDevice());
  
          // The aspect ratio depends on the backbuffer dimensions, which can 
          // possibly change after a reset.  So rebuild the projection matrix.
          buildProjMtx();
  }
  
  void ShadowDemo::updateScene(float dt)
  {
          mGfxStats->update(dt);
  
          // Get snapshot of input devices.
          gDInput->poll();
  
          // Check input.
          if( gDInput->keyDown(DIK_W) )         
                  mCameraHeight   += 25.0f * dt;
          if( gDInput->keyDown(DIK_S) )         
                  mCameraHeight   -= 25.0f * dt;
  
          // Divide by 50 to make mouse less sensitive. 
          mCameraRotationY += gDInput->mouseDX() / 100.0f;
          mCameraRadius    += gDInput->mouseDY() / 25.0f;
  
          // If we rotate over 360 degrees, just roll back to 0
          if( fabsf(mCameraRotationY) >= 2.0f * D3DX_PI ) 
                  mCameraRotationY = 0.0f;
  
          // Don't let radius get too small.
          if( mCameraRadius < 3.0f )
                  mCameraRadius = 3.0f;
  
          // The camera position/orientation relative to world space can 
          // change every frame based on input, so we need to rebuild the
          // view matrix every frame with the latest changes.
          buildViewMtx();
  
          // Update teapot position by modifying the translation elements
          // in its world matrix.
          if( gDInput->keyDown(DIK_A) )         
                  mTeapotWorld(3,0)   -= 2.0f * dt;
          if( gDInput->keyDown(DIK_D) )         
                  mTeapotWorld(3,0)   += 2.0f * dt;
  }
  
  void ShadowDemo::drawScene()
  {
          // Clear the backbuffer and depth buffer.
          HR(gd3dDevice->Clear(0, 0, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER |
                  D3DCLEAR_STENCIL, 0xffeeeeee, 1.0f, 0));
  
          HR(gd3dDevice->BeginScene());
  
          HR(mFX->SetTechnique(mhTech));
          HR(mFX->SetValue(mhLightVecW, &mLightVecW, sizeof(D3DXVECTOR3)));
          HR(mFX->SetValue(mhDiffuseLight, &mDiffuseLight, sizeof(D3DXCOLOR)));
          HR(mFX->SetValue(mhAmbientLight, &mAmbientLight, sizeof(D3DXCOLOR)));
          HR(mFX->SetValue(mhSpecularLight, &mSpecularLight, sizeof(D3DXCOLOR)));
  
          // All objects use the same material (except the shadow).
          HR(mFX->SetValue(mhAmbientMtrl, &mWhiteMtrl.ambient, sizeof(D3DXCOLOR)));
          HR(mFX->SetValue(mhDiffuseMtrl, &mWhiteMtrl.diffuse, sizeof(D3DXCOLOR)));
          HR(mFX->SetValue(mhSpecularMtrl, &mWhiteMtrl.spec, sizeof(D3DXCOLOR)));
          HR(mFX->SetFloat(mhSpecularPower, mWhiteMtrl.specPower));
  
          drawRoom();
          drawMirror();
          drawTeapot();
          drawReflectedTeapot();
  
          HR(mFX->SetValue(mhAmbientMtrl, &mShadowMtrl.ambient, sizeof(D3DXCOLOR)));
          HR(mFX->SetValue(mhDiffuseMtrl, &mShadowMtrl.diffuse, sizeof(D3DXCOLOR)));
          HR(mFX->SetValue(mhSpecularMtrl, &mShadowMtrl.spec, sizeof(D3DXCOLOR)));
          HR(mFX->SetFloat(mhSpecularPower, mShadowMtrl.specPower));
          drawTeapotShadow();
  
          mGfxStats->display();
  
          HR(gd3dDevice->EndScene());
  
          // Present the backbuffer.
          HR(gd3dDevice->Present(0, 0, 0, 0));
  }
  
  void ShadowDemo::buildRoomGeometry()
  {
          // Create and specify geometry.  For this sample we draw a floor
          // and a wall with a mirror on it.  We put the floor, wall, and
          // mirror geometry in one vertex buffer.
          //
      //   |----|----|----|
      //   |Wall|Mirr|Wall|
          //   |    | or |    |
      //   /--------------/
      //  /   Floor      /
          // /--------------/
  
          // Create the vertex buffer.
          HR(gd3dDevice->CreateVertexBuffer(24 * sizeof(VertexPNT), D3DUSAGE_WRITEONLY,
                  0, D3DPOOL_MANAGED,        &mRoomVB, 0));
  
          // Write box vertices to the vertex buffer.
          VertexPNT* v = 0;
          HR(mRoomVB->Lock(0, 0, (void**)&v, 0));
  
          // Floor: Observe we tile texture coordinates.
          v[0] = VertexPNT(-7.5f, 0.0f, -10.0f, 0.0f, 1.0f, 0.0f, 0.0f, 4.0f);
          v[1] = VertexPNT(-7.5f, 0.0f,   0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f);
          v[2] = VertexPNT( 7.5f, 0.0f,   0.0f, 0.0f, 1.0f, 0.0f, 4.0f, 0.0f);
          
          v[3] = VertexPNT(-7.5f, 0.0f, -10.0f, 0.0f, 1.0f, 0.0f, 0.0f, 4.0f);
          v[4] = VertexPNT( 7.5f, 0.0f,   0.0f, 0.0f, 1.0f, 0.0f, 4.0f, 0.0f);
          v[5] = VertexPNT( 7.5f, 0.0f, -10.0f, 0.0f, 1.0f, 0.0f, 4.0f, 4.0f);
  
          // Wall: Observe we tile texture coordinates, and that we
          // leave a gap in the middle for the mirror.
          v[6]  = VertexPNT(-7.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 2.0f);
          v[7]  = VertexPNT(-7.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f);
          v[8]  = VertexPNT(-2.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 2.0f, 0.0f);
          
          v[9]  = VertexPNT(-7.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 2.0f);
          v[10] = VertexPNT(-2.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 2.0f, 0.0f);
          v[11] = VertexPNT(-2.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 2.0f, 2.0f);
  
          v[12] = VertexPNT(2.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 2.0f);
          v[13] = VertexPNT(2.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f);
          v[14] = VertexPNT(7.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 2.0f, 0.0f);
          
          v[15] = VertexPNT(2.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 2.0f);
          v[16] = VertexPNT(7.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 2.0f, 0.0f);
          v[17] = VertexPNT(7.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 2.0f, 2.0f);
  
          // Mirror
          v[18] = VertexPNT(-2.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f);
          v[19] = VertexPNT(-2.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f);
          v[20] = VertexPNT( 2.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f);
          
          v[21] = VertexPNT(-2.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f);
          v[22] = VertexPNT( 2.5f, 5.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f);
          v[23] = VertexPNT( 2.5f, 0.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f);
  
          HR(mRoomVB->Unlock());
  }
  
  void ShadowDemo::buildFX()
  {
          // Create the FX from a .fx file.
          ID3DXBuffer* errors = 0;
          HR(D3DXCreateEffectFromFile(gd3dDevice, "DirLightTex.fx", 
                  0, 0, D3DXSHADER_DEBUG, 0, &mFX, &errors));
          if( errors )
                  MessageBox(0, (char*)errors->GetBufferPointer(), 0, 0);
  
          // Obtain handles.
          mhTech          = mFX->GetTechniqueByName("DirLightTexTech");
          mhWVP           = mFX->GetParameterByName(0, "gWVP");
          mhWorldInvTrans = mFX->GetParameterByName(0, "gWorldInvTrans");
          mhLightVecW     = mFX->GetParameterByName(0, "gLightVecW");
          mhDiffuseMtrl   = mFX->GetParameterByName(0, "gDiffuseMtrl");
          mhDiffuseLight  = mFX->GetParameterByName(0, "gDiffuseLight");
          mhAmbientMtrl   = mFX->GetParameterByName(0, "gAmbientMtrl");
          mhAmbientLight  = mFX->GetParameterByName(0, "gAmbientLight");
          mhSpecularMtrl  = mFX->GetParameterByName(0, "gSpecularMtrl");
          mhSpecularLight = mFX->GetParameterByName(0, "gSpecularLight");
          mhSpecularPower = mFX->GetParameterByName(0, "gSpecularPower");
          mhEyePos        = mFX->GetParameterByName(0, "gEyePosW");
          mhWorld         = mFX->GetParameterByName(0, "gWorld");
          mhTex           = mFX->GetParameterByName(0, "gTex");
  }
  
  void ShadowDemo::buildViewMtx()
  {
          float x = mCameraRadius * cosf(mCameraRotationY);
          float z = mCameraRadius * sinf(mCameraRotationY);
          D3DXVECTOR3 pos(x, mCameraHeight, z);
          D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);
          D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);
          D3DXMatrixLookAtLH(&mView, &pos, &target, &up);
  
          HR(mFX->SetValue(mhEyePos, &pos, sizeof(D3DXVECTOR3)));
  }
  
  void ShadowDemo::buildProjMtx()
  {
          float w = (float)md3dPP.BackBufferWidth;
          float h = (float)md3dPP.BackBufferHeight;
          D3DXMatrixPerspectiveFovLH(&mProj, D3DX_PI * 0.25f, w/h, 1.0f, 5000.0f);
  }
  
  void ShadowDemo::drawRoom()
  {
          HR(mFX->SetMatrix(mhWVP, &(mRoomWorld*mView*mProj)));
          D3DXMATRIX worldInvTrans;
          D3DXMatrixInverse(&worldInvTrans, 0, &mRoomWorld);
          D3DXMatrixTranspose(&worldInvTrans, &worldInvTrans);
          HR(mFX->SetMatrix(mhWorldInvTrans, &worldInvTrans));
          HR(mFX->SetMatrix(mhWorld, &mRoomWorld));
  
          HR(gd3dDevice->SetVertexDeclaration(VertexPNT::Decl));
          HR(gd3dDevice->SetStreamSource(0, mRoomVB, 0, sizeof(VertexPNT)));
  
          // Begin passes.
          UINT numPasses = 0;
          HR(mFX->Begin(&numPasses, 0));
          for(UINT i = 0; i < numPasses; ++i)
          {
                  HR(mFX->BeginPass(i));
  
                  // draw the floor
                  HR(mFX->SetTexture(mhTex, mFloorTex));
                  HR(mFX->CommitChanges());
                  HR(gd3dDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2));
  
                  // draw the walls
                  HR(mFX->SetTexture(mhTex, mWallTex));
                  HR(mFX->CommitChanges());
                  HR(gd3dDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 6, 4));
  
                  HR(mFX->EndPass());
          }
          HR(mFX->End());
  }
  
  void ShadowDemo::drawMirror()
  {
          HR(mFX->SetMatrix(mhWVP, &(mRoomWorld*mView*mProj)));
          D3DXMATRIX worldInvTrans;
          D3DXMatrixInverse(&worldInvTrans, 0, &mRoomWorld);
          D3DXMatrixTranspose(&worldInvTrans, &worldInvTrans);
          HR(mFX->SetMatrix(mhWorldInvTrans, &worldInvTrans));
          HR(mFX->SetMatrix(mhWorld, &mRoomWorld));
          HR(mFX->SetTexture(mhTex, mMirrorTex));
  
          HR(gd3dDevice->SetVertexDeclaration(VertexPNT::Decl));
          HR(gd3dDevice->SetStreamSource(0, mRoomVB, 0, sizeof(VertexPNT)));
  
          // Begin passes.
          UINT numPasses = 0;
          HR(mFX->Begin(&numPasses, 0));
          for(UINT i = 0; i < numPasses; ++i)
          {
                  HR(mFX->BeginPass(i));
  
                  // draw the mirror
                  HR(gd3dDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 18, 2));
  
                  HR(mFX->EndPass());
          }
          HR(mFX->End());
  }
  
  void ShadowDemo::drawTeapot()
  {
          // Cylindrically interpolate texture coordinates.
          HR(gd3dDevice->SetRenderState(D3DRS_WRAP0, D3DWRAPCOORD_0));
  
          HR(mFX->SetMatrix(mhWVP, &(mTeapotWorld*mView*mProj)));
          D3DXMATRIX worldInvTrans;
          D3DXMatrixInverse(&worldInvTrans, 0, &mTeapotWorld);
          D3DXMatrixTranspose(&worldInvTrans, &worldInvTrans);
          HR(mFX->SetMatrix(mhWorldInvTrans, &worldInvTrans));
          HR(mFX->SetMatrix(mhWorld, &mTeapotWorld));
          HR(mFX->SetTexture(mhTex, mTeapotTex));
  
          // Begin passes.
          UINT numPasses = 0;
          HR(mFX->Begin(&numPasses, 0));
          for(UINT i = 0; i < numPasses; ++i)
          {
                  HR(mFX->BeginPass(i));
                  HR(mTeapot->DrawSubset(0));
                  HR(mFX->EndPass());
          }
          HR(mFX->End());
  
          // Disable wrap.
          HR(gd3dDevice->SetRenderState(D3DRS_WRAP0, 0));
  }
  
  void ShadowDemo::drawReflectedTeapot()
  {
          HR(gd3dDevice->SetRenderState(D3DRS_STENCILENABLE,    true));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILFUNC,      D3DCMP_ALWAYS));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILREF,       0x1));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILMASK,      0xffffffff));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILWRITEMASK, 0xffffffff));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILZFAIL,     D3DSTENCILOP_KEEP));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILFAIL,      D3DSTENCILOP_KEEP));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILPASS,      D3DSTENCILOP_REPLACE));
  
          // disable writes to the depth and back buffers
      HR(gd3dDevice->SetRenderState(D3DRS_ZWRITEENABLE, false));
      HR(gd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, true));
      HR(gd3dDevice->SetRenderState(D3DRS_SRCBLEND,  D3DBLEND_ZERO));
      HR(gd3dDevice->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_ONE));
  
          // Draw mirror to stencil only.
          drawMirror();
  
          // Re-enable depth writes
          HR(gd3dDevice->SetRenderState( D3DRS_ZWRITEENABLE, true ));
  
          // Only draw reflected teapot to the pixels where the mirror
          // was drawn to.
          HR(gd3dDevice->SetRenderState(D3DRS_STENCILFUNC,  D3DCMP_EQUAL));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILPASS,  D3DSTENCILOP_KEEP));
  
          // Build Reflection transformation.
          D3DXMATRIX R;
          D3DXPLANE plane(0.0f, 0.0f, 1.0f, 0.0f); // xy plane
          D3DXMatrixReflect(&R, &plane);
  
          // Save the original teapot world matrix.
          D3DXMATRIX oldTeapotWorld = mTeapotWorld;
  
          // Add reflection transform.
          mTeapotWorld = mTeapotWorld * R;
  
          // Reflect light vector also.
          D3DXVECTOR3 oldLightVecW = mLightVecW;
          D3DXVec3TransformNormal(&mLightVecW, &mLightVecW, &R);
          HR(mFX->SetValue(mhLightVecW, &mLightVecW, sizeof(D3DXVECTOR3)));
  
          // Disable depth buffer and render the reflected teapot.
          HR(gd3dDevice->SetRenderState(D3DRS_ZENABLE, false));
          HR(gd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, false));
  
          // Finally, draw the reflected teapot
          HR(gd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CW));
          drawTeapot();
          mTeapotWorld = oldTeapotWorld;
          mLightVecW   = oldLightVecW;
          
          // Restore render states.
          HR(gd3dDevice->SetRenderState(D3DRS_ZENABLE, true));
          HR(gd3dDevice->SetRenderState( D3DRS_STENCILENABLE, false));
          HR(gd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW));
  }
  
  void ShadowDemo::drawTeapotShadow()
  {
          HR(gd3dDevice->SetRenderState(D3DRS_STENCILENABLE,    true));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILFUNC,      D3DCMP_EQUAL));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILREF,       0x0));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILMASK,      0xffffffff));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILWRITEMASK, 0xffffffff));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILZFAIL,     D3DSTENCILOP_KEEP));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILFAIL,      D3DSTENCILOP_KEEP));
      HR(gd3dDevice->SetRenderState(D3DRS_STENCILPASS,      D3DSTENCILOP_INCR)); 
  
          // Position shadow.
          D3DXVECTOR4 lightDirection(0.577f, -0.577f, 0.577f, 0.0f);
          D3DXPLANE groundPlane(0.0f, -1.0f, 0.0f, 0.0f);
  
          D3DXMATRIX S;
          D3DXMatrixShadow(&S, &lightDirection, &groundPlane);
  
          // Offset the shadow up slightly so that there is no
          // z-fighting with the shadow and ground.
          D3DXMATRIX eps;
          D3DXMatrixTranslation(&eps, 0.0f, 0.001f, 0.0f);
  
          // Save the original teapot world matrix.
          D3DXMATRIX oldTeapotWorld = mTeapotWorld;
  
          // Add shadow projection transform.
          mTeapotWorld = mTeapotWorld * S * eps;
  
          // Alpha blend the shadow.
          HR(gd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, true));
          HR(gd3dDevice->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA));
          HR(gd3dDevice->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA));
  
          drawTeapot();
  
          // Restore settings.
          mTeapotWorld = oldTeapotWorld;
          HR(gd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, false));
          HR(gd3dDevice->SetRenderState(D3DRS_STENCILENABLE,    false));
  }
  
  void ShadowDemo::genSphericalTexCoords()
  {
          // D3DXCreate* functions generate vertices with position 
          // and normal data.  But for texturing, we also need
          // tex-coords.  So clone the mesh to change the vertex
          // format to a format with tex-coords.
  
          D3DVERTEXELEMENT9 elements[64];
          UINT numElements = 0;
          VertexPNT::Decl->GetDeclaration(elements, &numElements);
  
          ID3DXMesh* temp = 0;
          HR(mTeapot->CloneMesh(D3DXMESH_SYSTEMMEM, 
                  elements, gd3dDevice, &temp));
  
          ReleaseCOM(mTeapot);
  
          // Now generate texture coordinates for each vertex.
          VertexPNT* vertices = 0;
          HR(temp->LockVertexBuffer(0, (void**)&vertices));
  
          for(UINT i = 0; i < temp->GetNumVertices(); ++i)
          {
                  // Convert to spherical coordinates.
                  D3DXVECTOR3 p = vertices[i].pos;
          
                  float theta = atan2f(p.z, p.x);
                  float phi   = acosf(p.y / sqrtf(p.x*p.x+p.y*p.y+p.z*p.z));
  
                  // Phi and theta give the texture coordinates, but are not in 
                  // the range [0, 1], so scale them into that range.
  
                  float u = theta / (2.0f*D3DX_PI);
                  float v = phi   / D3DX_PI;
                  
                  // Save texture coordinates.
                  
                  vertices[i].tex0.x = u;
                  vertices[i].tex0.y = v;
          }
          HR(temp->UnlockVertexBuffer());
  
          // Clone back to a hardware mesh.
          HR(temp->CloneMesh(D3DXMESH_MANAGED | D3DXMESH_WRITEONLY,
                  elements, gd3dDevice, &mTeapot));
  
          ReleaseCOM(temp);
  }