The projectUV operation creates the final texture coordinates of the selected uv-set by applying the corresponding projection matrix. Thus, this operation 'bakes' the texture projection into the texture coordinates of the geometry of the current shape. The projection is based on the uvw-coordinate system specified by the setupProjection operation.
Colormap has uvSet 0, bumpmap will have uvSet 1, dirtmap has uvSet 2.
Please refer to the examples in the setupProjection reference.