This method clears the viewport — or a set of rectangles in the viewport — to a specified RGBA color, clears the depth buffer, and erases the stencil buffer.
HRESULT Clear( DWORD Count, CONST RECT* pRects, DWORD Flags, D3DMCOLOR Color, float Z, DWORD Stencil );
[in] Number of rectangles in the array at pRects. If you set pRects to NULL, this parameter must be set to 0.
[in] Pointer to an array of RECT structures that describe the rectangles to clear. Set a rectangle to the dimensions of the rendering target to clear the entire surface. Each rectangle uses screen coordinates that correspond to points on the render target surface. Coordinates are clipped to the bounds of the viewport rectangle. This parameter can be set to NULL to indicate that the entire viewport rectangle is to be cleared.
[in] Flags that indicate which surfaces should be cleared. This parameter can be any combination of the following D3DMCLEAR Values.
Clear the stencil buffer to the value in the Stencil parameter.
Clear the render target to the color in the Color parameter.
Clear the depth buffer to the value in the Z parameter.
[in] A 32-bit ARGB color value to which the render target surface is cleared.
[in] New z value that this method stores in the depth buffer. This parameter can be in the range from 0.0 through 1.0 (for z-based or w-based depth buffers). A value of 0.0 represents the nearest distance to the viewer, and 1.0 the farthest distance.
[in] Integer value to store in each stencil-buffer entry. This parameter can be in the range from 0 through 2n1, where n is the bit depth of the stencil buffer.