The use of 3D assets to perform technical analysis on scenes: determine camera type, lenses, rigging, portions of sets which need to be physically built vs. virtual, stunts, etc. Techvis often includes physically accurate digital camera rigs (eg, a motion control system or technocrane) and when used in ICVFX workflows, can also show if planned shots are ‘volume-friendly’.
This image shows previs vs final shot. The previs was provided by The Third Floor, Inc.