Programming with DirectX : Implementing Per-Pixel Lighting (part 2) - The Main Source File

The Main Source File

In the main source file, two new objects are added to the global section: one to pass the light position to the shaders and one to pass the camera position. The end of the global section with the new variables in the Lighting demo are shown in Listing 1. In the InitializeDemo() function, these effect variables are obtained so we can use them to actually pass data to the shaders. The InitializeDemo() function is partially shown in Listing 2. The only new code in it is the effect variable calls that obtain access so we can set the light and camera position.

Listing 1. Partial Look at the Lighting Demo’s Global Variables

…

ID3D10Effect *g_shader = NULL;
ID3D10EffectTechnique *g_lightingTech = NULL;
ID3D10EffectVectorVariable *g_lightPosEffectVar = NULL;
ID3D10EffectVectorVariable *g_eyePosEffectVar = NULL;
ID3D10EffectMatrixVariable *g_worldEffectVar = NULL;
ID3D10EffectMatrixVariable *g_viewEffectVar = NULL;
ID3D10EffectMatrixVariable *g_projEffectVar = NULL;

D3DXMATRIX g_worldMat, g_viewMat, g_projMat;


// Scene rotations.
float g_xRot = 0.0f;
float g_yRot = 0.0f;

Listing 2. Partial Look at the `InitializeDemo()` Function

bool InitializeDemo()
{
  // Load the shader.

  DWORD shaderFlags = D3D10_SHADER_ENABLE_STRICTNESS;

#if defined( DEBUG ) || defined( _DEBUG )
   shaderFlags |= D3D10_SHADER_DEBUG;
#endif

   ID3D10Blob *errors = NULL;

   HRESULT hr = D3DX10CreateEffectFromFile("LambertBlinnPhong.fx",
      NULL, NULL, "fx_4_0", shaderFlags, 0, g_d3dDevice, NULL,
      NULL, &g_shader, &errors, NULL);

   if(errors != NULL)
   {
      MessageBox(NULL, (LPCSTR)errors->GetBufferPointer(),
                 "Error in Shader!", MB_OK);

      errors->Release()
   }

   if(FAILED(hr))
      return false;

   g_lightingTech = g_shader->GetTechniqueByName(
      "BlinnPhongSpecular");

   g_worldEffectVar = g_shader->GetVariableByName(
      "World")->AsMatrix();

   g_viewEffectVar = g_shader->GetVariableByName(
      "View")->AsMatrix();

   g_projEffectVar = g_shader->GetVariableByName(
      "Projection")->AsMatrix();

   g_lightPosEffectVar = g_shader->GetVariableByName(
      "lightPos")->AsVector();

   g_eyePosEffectVar = g_shader->GetVariableByName(
      "eyePos")->AsVector();

   …

   return true;
}

In the Update() function the world matrix is rotated along the X and Y axes so we can see the specular lighting changes as the orientation moves in real time. In the RenderScene() function the only new code is the code that passes the light and camera positions to the shaders. The light position is located 5 units along the negative Z axis, while the camera position is located at the origin. The object itself is positioned 6 units along the Z axis, which can be seen in the Update() function.

The Update() and RenderScene() functions are shown in Listing 3. Figure 1 shows a screenshot from the running demo.

Listing 3. The `Update()` and `RenderScene()` Functions from the Lighting Demo

void Update()
{
   g_xRot += 0.0001f;
   g_yRot += 0.0002f;

   if(g_xRot < 0) g_xRot = 359;
   else if(g_xRot >= 360) g_xRot = 0;

   if(g_yRot < 0) g_yRot = 359;
   else if(g_yRot >= 360) g_yRot = 0;

   D3DXMATRIX trans, rotX, rotY;

   D3DXMatrixRotationX(&rotX, g_xRot);
   D3DXMatrixRotationY(&rotY, g_yRot);
   D3DXMatrixTranslation(&trans, 0, 0, 6);

   g_worldMat = (rotX * rotY) * trans;
}


void RenderScene()
{
   float col[4] = { 0, 0, 0, 1 };

   g_d3dDevice->ClearRenderTargetView(g_renderTargetView, col);
   g_d3dDevice->ClearDepthStencilView(g_depthStencilView,
                                    D3D10_CLEAR_DEPTH, 1.0f, 0);

   g_d3dDevice->IASetInputLayout(g_layout);
   g_d3dDevice->IASetPrimitiveTopology(
      D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST);

   D3D10_TECHNIQUE_DESC techDesc;
   g_lightingTech->GetDesc(&techDesc);

   unsigned int stride = sizeof(DX10Vertex);
   unsigned int offset = 0;

   float lightPos[4] = { 0, 0, -5, 1 };
   float eyePos[4] = { 0, 0, 0, 1 };

   g_worldEffectVar->SetMatrix((float*)&g_worldMat);
   g_lightPosEffectVar->SetFloatVector(lightPos);
   g_eyePosEffectVar->SetFloatVector(eyePos);

   for(int m = 0; m < (int)g_meshes.size(); m++)
   {
      g_d3dDevice->IASetVertexBuffers(0, 1,
         &g_meshes[m].m_vertices, &stride, &offset);

      for(unsigned int i = 0; i < techDesc.Passes; i++)
      {
         g_lightingTech->GetPassByIndex(i)->Apply(0);
         g_d3dDevice->Draw(g_meshes[m].m_totalVerts, 0);
      }
   }

   g_swapChain->Present(0, 0);

   Update();
}