3D imaging has become a frequently used method for gathering quantitative rock mass data and documenting in situ rock mass conditions after excavation. As a supplement to conventional geological mapping, it increases working safety and improves data completeness. The method is fast and easy to apply, and provides a permanent, objective, accurate, and detailed 3D record of the rock mass. Apart from the documentation, the results of a 3D image analysis form a part of the final support design and allow for the prediction of the rock mass conditions. This paper briefly reviews the 3D imaging technology following the computer vision principle and subsequently the additional possibilities for the registration of 3D images without the need for any external surveying system. After describing the capabilities for geological mapping, a recent extension of the technology is given where instant geological mapping on digital photographs right in front of a tunnel face is performed and measurements are upgraded to 3D information.