Perspective provides ways of spatialising, examining and representing reality. Technical perspective, in particular, uses systematic methods to probe a spatial reality and produce an image or structured representation of it.
Every perspective image is therefore, to some degree, an abstraction of reality. It selects, transforms or represents aspects of a spatial scene rather than reproducing the physical world in its entirety.
Levels of abstraction can be understood as a bridge between the concreteness of physical reality and increasingly abstract forms of description, modelling and representation. Visual abstraction creates a meaningful visual representation of something, whether its source is physical, mathematical or imaginary.
Modern imaging and new-media systems greatly extend these possibilities. They allow us to move between different scales and levels of representation; examine wholes and parts, interiors and exteriors; and relate physical objects, images, models and ideas.
Perspective and Multiple Realities
Another way of understanding perspective is to distinguish between different kinds of spatial reality that may be viewed, modelled, represented or imagined.
Physical Reality
Physical Reality is the physical world or actual spatial reality comprising objects, environments and the wider physical universe.
Mathematical Reality
Mathematical Reality is a modelled world: a mathematical or geometrical abstraction used to describe, analyse or approximate aspects of physical or other spatial realities.
Artificial Reality
Artificial Reality is a human-made representation of a physical, mathematical or imaginary reality. Examples include drawings, paintings, photographs, films, computer models, graphics and Virtual Reality systems.
Imaginary Reality
Imaginary Reality is a spatial reality formed or conceived in the human mind.
Perspective can operate between these realities, allowing one form of spatial information to be viewed, represented, modelled or interpreted through another.
From Spatial Reality to Optical Images
Optical perspective is concerned with forming and analysing images of spatial reality.
An optical image is generally produced from a particular viewpoint and can provide information about the three-dimensional forms and spatial relations from which it arises. However, an image does not necessarily provide enough information to determine the structure of those forms unambiguously.
This gives rise to the equivalence problem: different spatial arrangements can potentially produce the same or very similar optical information, so contextual and other evidence may be needed to infer the underlying spatial reality.
Graphical systems such as linear perspective provide one means of systematically encoding and decoding spatial information through known geometrical structures and relations.
Three Interrelated Worlds
Perspective can also be understood through three closely related but distinct worlds: the Physical World, the Optical World and the Visual World.
The Physical World
The Physical World consists of the objects and spatial scenes that exist in physical reality.
The Optical World
The Optical World concerns the changing appearance of those objects as light is emitted, reflected, transmitted or otherwise conveyed to an eye, camera, instrument or detector.
It therefore mediates between physical spatial reality and the images through which that reality may be observed or recorded.
A central concern of optical perspective is to use the Optical World to examine, represent and understand the Physical World.
The Visual World
The Visual World is the world produced through human vision: the transformation and interpretation of optical information through the physiological and psychological processes of sight.
It is therefore related to, but not identical with, either the Physical World or the Optical World.
Mapping Between Worlds
Humans also create represented and modelled worlds based upon physical, optical and visual realities.
Perspective provides many of the principles, phenomena, methods and systems through which relationships between these worlds can be established.
These mappings are not always simple or exact. A physical object, its optical appearance, its human visual appearance and its represented image may correspond closely in some respects while differing substantially in others.
Understanding these different levels of abstraction is therefore fundamental to understanding how perspective connects reality, appearance, vision, modelling and representation.