After an initial 3D model has been created and verified through measurement or through a CAD program, you can go back to the photographs and from them add more feature detail. If the first 3D model is only a rough outline, you can zoom in and add point and line marks on detailed features.
If the initial model has no surface elements and you are using the model for 3D visualization or rendering work, then adding Surfaces to the model before export would be a good idea. See Creating Surfaces.
Once additional detail has been marked and referenced, you can reprocess the 3D model to create 3D information for the newly added features.
Note: You do not need to reprocess the project if all you have added to an already processed project, is Surfaces. Surfaces use the 3D points that are already there and do not create new ones.