Storing Bitmaps in Display Memory

Blitting from display memory to display memory is usually much more efficient than blitting from system memory to display memory. As a result, you should store as many of the sprites your application uses as possible in display memory.

Most display adapter hardware contains enough extra memory to store more than only the primary surface and the back buffer. You can use the dwVidMemTotal and dwVidMemFree members of the DDCAPS structure (if you used the IDirectDraw2::GetCaps method to get the capabilities of the user's display hardware) to determine the amount of available memory for storing bitmaps in the display adapter's memory. If you want to see how this works, use the DirectX Viewer sample application included with the DirectX APIs in the Platform SDK. Under DirectDraw Devices, open the Primary Display Driver folder, and then open the General folder. The amount of total display memory (minus the primary surface) and the amount of free memory is displayed. Each time a surface is added to the DirectDraw object, the amount of free memory decreases by the amount of memory used by the added surface.