Vertex pipeline
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Vertex Pipeline Oerview
The function of the vertex pipeline in any GPU is to take geometry data(usually supplied as vector points), work with it if needed (with either fixed function processes(Earlier DirectX Version primiarliy), or a vertex shader program(later DirectX Versions primarily)), and create all of the 3D data points in a scene to a 2D plane for display on a flat monitor. It is possible to eliminate unneeded data from going through the rendering pipeline to cut out extroneous work (called view volume clipping and backface culling). After the vertex engine is done working with the geometry, all the 2D calcualted data is sent to the pixel engine for further processing (like texturing and fragment shading).
As of Direct X 9c, the vertex processor is able to do the following by programming the vertex processing under the Direct X API: Tessellation Displacement Mapping Geometry Blending Higher-Order Primitives Point Sprites Matrix Stacks