GMA X3000 supports the D3D occlusion query capability, which can be used to reduce overdraw.
Refer to IDirect3DDevice9::CreateQuery(). This query capability can be used to count the number of pixels that passed the Z test. With this you can determine if an object is potentially visible by rendering its bounding box. If the query returns zero then the bounding box was not visible so there is no need to render the object. This can provide a very large performance boost when it is used on complex objects such as trees that contain hundreds of branches and leaves. The technique should not be used on simple objects since the bounding box test could be more expensive than simply rendering the object. When rendering the bounding box be sure to turn off both Z writes and color writes.
