Goals of Perspective

The Goals of Perspective describe what a perspective process, method or system is intended to achieve.

Perspective is not concerned only with making drawings appear three-dimensional. Across vision, optics, measurement, representation, photography, instruments and New Media, perspective enables humans to observe, image, measure, model, represent and explore spatial reality, as well as to create convincing illusions and immersive visual environments.

At the broadest level, the central human goal of perspective can be described as visual knowledge: acquiring, organising and communicating knowledge about spatial reality through views, images, measurements, models and representations.

Goals within Perspective Category Theory

Within Perspective Category Theory (PCT), goals are distinguished from Perspective Categories, Classes, Types and Forms.

Perspective Category — identifies the principal source or mode of a perspective process;
Perspective Class — identifies the principal direction in which the process operates;
Perspective Type — identifies a particular method, system, process or subdivision;
Perspective Form — identifies the visual, optical, geometrical or spatial appearance produced;
Perspective Goal or Function — identifies what the process is intended to achieve;
Perspective Outcome or Product — identifies what results from the process.

This distinction is important because viewing, measuring, representing, illusion and immersion are not additional Perspective Classes. They are goals, functions or outcomes that may be achieved through either of the two directional classes or through systems in which both classes operate.

The central goal: visual knowledge

At the broadest human level, the central goal of perspective is the acquisition and organisation of visual knowledge.

Humans seek to know what exists in spatial reality, where things are located, how they are shaped, how large they are, how they relate to one another and how they change through time.

Much of this knowledge is acquired visually. In many circumstances involving great distance, very small scale, inaccessible environments or complex spatial structures, visual or instrument-generated information may provide the principal means by which physical reality can be examined.

Perspective therefore extends human vision by providing systematic methods for observing, recording, measuring, modelling and representing spatial objects and scenes.

Five principal human goals of perspective

Volume 1 groups the principal human goals of perspective into five broad goals:

Viewing reality — observing spatial Form;
Matching reality — measuring, surveying or modelling spatial Form;
Representing reality — copying or constructing images of spatial Forms;
Creating illusion — producing convincing appearances of spatial reality;
Producing immersion — enabling apparent or actual visual participation within a spatial reality.

These goals overlap considerably in practice. One perspective system may fulfil several of them simultaneously.

A broader operational list of goals

The Dictionary of Perspective expresses the Goals of Perspective in a more detailed operational form.

The principal goal terms are:

Viewing;
Imaging;
Projecting;
Measuring;
Matching;
Representing;
Creating illusion; and
Producing immersion.

This expanded list makes explicit several important operations that may occur within the broader five-goal framework, particularly imaging, projecting and measuring.

A single perspective system may pursue several of these goals at the same time or at different stages of its operation.

Viewing

Viewing is the goal of directly or indirectly observing a spatial object, scene, view or image.

It includes looking at physical spatial reality with the eyes as well as viewing through optical and technical instruments.

Viewing may involve:

direct observation;
visual inspection;
observation through optical instruments;
exploration of represented environments;
comparison of different viewpoints; and
observation of spatial relationships and Perspective Phenomena.

The immediate product may be a perspective view: a live or real-time visual relationship with the object, scene or image under examination.

Imaging

Imaging is the formation, capture, recording or presentation of a perspective image or view.

It may occur naturally through the eye or technically through cameras, microscopes, telescopes, scanners and other imaging instruments.

Imaging can preserve or transform information concerning:

size;
shape;
position;
orientation;
colour;
clarity;
depth;
surface structure; and
spatial relationships.

The goal is not necessarily to produce an artistic picture. Imaging can also provide scientific, technical, medical, navigational or analytical information about spatial reality.

Projecting

Projecting concerns sending light, images, shadows, lines or spatial information forwards from a source or representational system.

Projection is therefore a goal or operation associated particularly with the Projecting Class.

Examples include:

projecting an image onto a screen;
casting a shadow;
graphically projecting lines from a station point;
optically projecting light into physical space;
displaying generated imagery within a viewing environment; and
projecting information into virtual or augmented spatial systems.

Projection can be used to represent, measure, communicate, illuminate, create illusion or produce immersion.

Measuring

Measuring uses perspective relationships to obtain quantitative or spatial information about objects, scenes or images.

Perspective can assist in determining or comparing:

size;
shape;
scale;
distance;
position;
angle;
orientation;
proportion; and
other spatial relationships.

Measurement may be direct, graphical, optical, mathematical, instrument-based or computational.

Surveying, photogrammetry, mapping, scientific imaging and computer vision demonstrate that perspective is not simply a system for producing appearances: it can also be used to obtain structured information from spatial reality.

Matching

Matching is one of the fundamental functions and goals of perspective.

It concerns measuring or evaluating images and views in relation to known spatial forms, standards, impressions or measuring scales.

Matching may involve:

figuring and calculating;
surveying;
classifying;
segmenting;
comparing and identifying;
mapping;
indexing and gauging;
cross-matching;
orienting and navigating;
prescribing and certifying; and
comparing represented forms with physical spatial reality.

Perspective therefore provides a means of relating the structure of an image or view to the structure of the object or scene from which it is derived.

Representing

Representing is the goal of producing a visual, graphical, optical, mathematical or computational representation of spatial reality.

A representation may copy, model, describe, reconstruct or transform an object or scene.

Perspective representations include:

drawings;
paintings;
diagrams;
photographs;
maps;
films;
computer-generated images;
three-dimensional models;
scientific visualisations; and
virtual environments.

The goal may be realism, analysis, communication, design, documentation, prediction or exploration rather than merely visual imitation.

Creating illusion

Creating illusion is the goal of producing an appearance that causes the viewer to experience a spatial relationship that differs in some respect from the underlying physical or represented reality.

Perspective illusions can affect apparent:

size;
depth;
distance;
position;
shape;
scale;
transparency; or
spatial organisation.

Linear-perspective drawings can create an impression of depth on a flat surface, while Forced, Simulated, Blended, Anamorphic and other Perspective Types can produce much more specialised spatial illusions.

Illusion is therefore an important goal of perspective, but it is only one among several.

Producing immersion

Immersion occurs when a perspective system creates the impression that the observer is situated within, surrounded by or able to participate in a represented or simulated spatial environment.

The goal may range from a simple apparent sense of spatial presence to interactive exploration of a three-dimensional environment.

Immersive perspective systems may include:

panoramic displays;
stereoscopic systems;
cinema;
virtual reality;
augmented reality;
mixed and extended reality; and
interactive New Media environments.

Immersion differs from ordinary representation because the observer’s apparent place within the visual or spatial system becomes an important part of the perspective experience.

One perspective system can have several goals

The Goals of Perspective should not be treated as mutually exclusive categories.

A single perspective system may view, image, measure, match, represent and project spatial information while also creating illusion or immersion.

A computer-based three-dimensional model, for example, may be used to:

represent an existing spatial environment;
measure its geometry;
compare alternative structures;
generate views from different positions;
display or project those views;
explore the environment interactively; and
produce an immersive visual experience.

The appropriate Goal of Perspective therefore depends upon what the system is being used to accomplish at a particular stage or in a particular application.

Goals and Functions of Perspective

Perspective Goals and Perspective Functions are closely related.

A goal describes what the perspective process is intended to achieve. A function describes the operation through which the system contributes towards that goal.

The functions of perspective include:

capturing;
observing;
prescribing;
measuring;
calculating;
classifying;
modelling;
surveying;
mapping;
indexing;
gauging;
certifying;
linking;
mixing;
exploring;
displaying; and
projecting.

These operations explain how perspective systems accomplish their broader goals.

Goals and Products of Perspective

A Goal of Perspective should also be distinguished from the Product or Outcome of Perspective.

The goal is what the process seeks to achieve. The product is what the process actually produces.

Typical products of perspective include:

a visual image;
a view;
a measurement;
a calculation;
a representation;
a model; or
a spatial appearance.

The relationship can therefore be expressed as:

Goal → Perspective Process or Function → Product or Outcome

For example:

Goal: measure spatial reality → surveying or imaging process → measured spatial data

or:

Goal: represent spatial reality → graphical or imaging process → perspective image or model

Perspective as a source of spatial data

The products of perspective can provide several different kinds of information about spatial reality.

These may include:

Subsumptive data — information about wholes and parts;
Ordinal data — information about figure, size, scale and position;
Determinative data — information concerning state and activity.

This reinforces the role of perspective as a means of acquiring and organising visual knowledge rather than merely producing pictures.

The historical goal of graphical perspective

Traditional accounts of graphical or Linear Perspective often describe its goal much more narrowly.

From the Renaissance onwards, one important goal was to imitate the appearance of spatial reality as if viewed through a window, preserving an impression of depth on a flat picture surface.

Perspective could therefore make depicted objects appear dimensional, suggest nearness or distance and create an apparent spatial environment within a picture.

This remains an important Goal of Perspective, but it represents only one part of the much larger modern field.

Perspective today also serves measurement, imaging, modelling, scientific observation, mapping, navigation, computer vision, virtual environments and many other applications that cannot adequately be described simply as attempts to imitate what the eye sees.

Perspective is more than illusion

Perspective is sometimes reduced to a technique for creating the visual illusion of three-dimensional depth on a two-dimensional surface.

This interpretation is too narrow.

Illusion and immersion are important goals, but perspective also enables humans to view, image, measure, match, model, represent and project information about the spatial world.

Its practical purpose is therefore much broader: to examine spatial reality in a detailed, systematic, realistic and analytical manner and to create visual models through which new spatial forms, relationships and possibilities can be explored.

Why the Goals of Perspective matter

Identifying the goal of a perspective system helps explain why that system exists and how its success should be judged.

A perspective method intended for measurement should not necessarily be evaluated according to the same criteria as one intended to produce illusion. A representation intended for scientific analysis may require different properties from an immersive entertainment environment.

The Goals of Perspective therefore provide an important analytical layer for understanding:

what a perspective process is intended to accomplish;
which functions are required to achieve that purpose;
which Perspective Categories, Classes and Types participate;
which products or outcomes are produced; and
how successfully the resulting perspective system fulfils its intended role.

At their broadest level, the Goals of Perspective concern the use of visual and optical processes to acquire, analyse, organise, represent and extend human knowledge of spatial reality.