Architectural Rendering Definition
Architectural rendering, or architectural illustration, is the art of creating two-dimensional images or animations showing the attributes of a proposed architectural design.
Images that are generated by a computer using three-dimensional modeling software or other computer software for presentation purposes are commonly termed 'Computer Generated Renderings'. Rendering techniques vary. Some methods create simple flat images or images with basic shadows. A popular technique uses sophisticated software to approximate accurate lighting and materials. This technique is often referred to as a 'Photo Real' rendering. Renderings are usually created for presentation, marketing and design analysis purposes.
3D Walk through and fly by animations (movie)
Photo realistic 3D Rendering
Realtime 3D Renderings
Light and Shadow (sciography) study renderings
Renovation Renderings (photomontage)
3D renderings play a major role in real estate sales. It also makes it possible to make design related decisions well before the building is actually built. Thus it helps experimenting with building design and its visual aspects.
Hand-Drawn Renderings or Architectural Illustration
Until 3D computer modeling became common, most architectural renderings were created by hand. There are still many architectural illustrators who create renderings entirely by hand. Some hand illustrators use a combination of hand and computer generated linework. Common mediums for hand architectural renderings include:
Pen and Ink
Paraphrased from Wikipedia: http://en.wikipedia.org/wiki/Architectural_rendering