Altiverb 6 from Audio Ease is a convolution based reverb plug-in for Mac OS X and Windows. Convolution reverb uses impulse response samples of real environments that can range, for example, from the Sydney Opera House to the cockpit of a Jumbo Jet.
The initial impulse that is used to "sweep" the acoustic space is a known factor. Once it is removed from the original sound file, the remaining information represents the acoustic response of the space in question.
However, this information is "static" in the sense that like a camera, the audio capture is done in a moment of time. And while it may be accurate, it may not suit the program material it is being used on. As a solution, Altiverb 6 offers an extensive set of editable parameters that include room size and reverb length, amongst others.
The software provides the ability for the users to sample their own spaces (Mac only,) or indeed other hardware reverb processors, allowing for countless possibilities. And there is nothing like applying a "real space" to, say a MIDI orchestral track for instance, to bring those sounds to life.