Most of the time framing for walls and roofs can be shown on a 2D plan or in sections cut through the building. For unusual or complication situations, though, a three dimensional model helps both the architect and the contractor understand what is needed.
For this small addition (click here for more images) the framing had to accommodate several special conditions. The attached video shows how it was done. Color coding helps the contractor see what type of framing material is needed in different places. White is standard lumber. Blue is engineered lumber (parallam framing) and green is LVL structural headers. The red stuff is HVAC coolant lines that have to be threaded through the framing to keep them hidden.