The UV projection node uses the Mesh's UV texture coordinates to map the texture onto the surface. It is not always necessary to connect a UV projection node to the texture, as UV projection is the default mapping method. However, it may be useful for mapping a texture to a surface that has multiple UV sets. The UV projection node has a single UV Set parameter, which specifies the UV set needed for the texture. The attribute is a numerical value that ranges from 1 - 3. Figure 1 shows the parameter for the UV projection node in the Maya® Attribute Editor.
Figure 1: UV Projection node parameters