Step 4: Rendering and Displaying a Scene

To render and display the scene, the sample code in this step clears the back buffer to a blue color, transfers the contents of the back buffer to the front buffer, and presents the front buffer to the screen.

To clear a scene, call the IDirect3DDevice9::Clear method.

// Clear the back buffer to a blue color
g_pd3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0,0,255), 1.0f, 0 );

The first two parameters accepted by IDirect3DDevice9::Clear inform Microsoft?Direct3D?of the size and address of the array of rectangles to be cleared. The array of rectangles describes the areas on the render target surface to be cleared.

In most cases, you use a single rectangle that covers the entire rendering target. You do this by setting the first parameter to 0 and the second parameter to NULL. The third parameter determines the method's behavior. You can specify a flag to clear a render-target surface, an associated depth buffer, the stencil buffer, or any combination of the three. This tutorial does not use a depth buffer, so D3DCLEAR_TARGET is the only flag used. The last three parameters are set to reflect clearing values for the render target, depth buffer, and stencil buffer. The CreateDevice sample project sets the clear color for the render target surface to blue (D3DCOLOR_XRGB(0,0,255)). The final two parameters are ignored by the IDirect3DDevice9::Clear method because the corresponding flags are not present.

After clearing the viewport, the CreateDevice sample project informs Direct3D that rendering will begin, then it signals that rendering is complete, as shown in the following code fragment.

// Begin the scene.
g_pd3dDevice->BeginScene();

// Rendering of scene objects happens here.

// End the scene.
g_pd3dDevice->EndScene();

The IDirect3DDevice9::BeginScene and IDirect3DDevice9::EndScene methods signal to the system when rendering is beginning or is complete. You can call rendering methods only between calls to these methods. Even if rendering methods fail, you should call EndScene before calling BeginScene again.

After rendering the scene, you display it by using the IDirect3DDevice9::Present method.

g_pd3dDevice->Present( NULL, NULL, NULL, NULL );

The first two parameters accepted by Present are a source rectangle and destination rectangle. The sample code in this step presents the entire back buffer to the front buffer by setting these two parameters to NULL. The third parameter sets the destination window for this presentation. Because this parameter is set to NULL, the hWndDeviceWindow member of D3DPRESENT_PARAMETERS is used. The fourth parameter is the DirtyRegion parameter and in most cases should be set to NULL.

The final step for this tutorial is shutting down the application, as described in Step 5: Shutting Down.