With the help of 3DA you can change different graphic options under DirectX 8 and OpenGL. 3DA changes different CAP-bits for example, if a game requires HW T&L 3DA emulates these bits and the games runs on graphic boards which don't have HW T&L capabilities. 3DA doesn't emulate any features in software(except cube mapping, which is done ith a simple 2D texture), like Pixel or Vertex Shader. 3DA is also a very nice tool for benchmarking. It generates detailed log files (CSV) with FPS and other parameters.