A Perspective Method is a repeatable procedure for viewing, forming, capturing, calculating, constructing, projecting, measuring, transferring, checking or representing a perspective image, view or spatial appearance.
Perspective is not one single method. Different perspective methods have been developed for direct observation, optical imaging, graphical construction, measurement, parallel and central projection, freehand drawing, computer modelling, image matching and many other purposes.
The essential question answered by a Perspective Method is therefore: How is the perspective operation actually carried out?
Definition of Perspective Method
Volume 1 defines a Perspective Method as a repeatable procedure that applies one or more perspective principles in order to form, calculate, record, project, measure or check a perspective view, image, representation or model.
A method can embody theoretical principles, mathematical formulae, physical or optical mechanisms, information-processing procedures and practical techniques.
Several methods can also operate together within the same perspective process or system.
Perspective Is Not a Single Method
Perspective is a broad interdisciplinary field involving natural appearance, human vision, optics, mathematics, graphical construction, instruments, simulation and computational media.
Consequently, the term perspective should not be understood as referring only to the familiar graphical construction of lines towards vanishing points.
An eye, camera, perspective window, geometrical construction, projector, measuring procedure or computer model can all participate in perspective through very different methods.
Perspective Principle and Perspective Method
A Perspective Principle and a Perspective Method are closely related but should be distinguished.
- Perspective Principle: the theoretical mechanism or relationship underlying a perspective process.
- Perspective Method: the repeatable procedure through which one or more such principles are applied.
A principle explains why or according to what relationship a perspective effect occurs; a method specifies how the operation is performed.
Perspective Method, Category, Class, Type and Form
The Dictionary distinguishes a Perspective Method from several other basic terms used within Perspective Category Theory:
- Perspective Category identifies the principal source or mode through which the perspective process is produced.
- Perspective Class identifies the principal direction in which the process operates.
- Perspective Type identifies a particular method, system, process or subdivision.
- Perspective Form is the visual, optical, geometrical or spatial appearance produced.
- Perspective Method describes how the perspective operation is carried out.
These concepts are related but they answer different questions about the same perspective process.
Perspective Method and Perspective Type
A Perspective Type can itself be defined by a particular method, system, process or subdivision. Consequently, Perspective Method and Perspective Type can overlap in terminology without being identical concepts.
The term Linear Perspective, for example, can refer to a geometrical type or system, while several different construction methods can be used to produce a linear-perspective image.
It is therefore important to distinguish the perspective configuration being produced from the particular procedure used to construct it.
Perspective Method and Perspective Form
A Perspective Method is also different from the Perspective Form that results from it.
Perspective Form refers to the visible, optical, geometrical or spatial appearance produced, including changes in apparent size, shape, convergence, colour, clarity, contrast, direction, curvature, compression, depth or immersion.
The method is the procedure; the Form is the resulting appearance.
Perspective as Method and Outcome
Many perspective terms are ambiguous because the same name can describe both a method and its resulting image or appearance.
Linear Perspective, for example, can describe a mathematical projection system, a graphical construction method, an optical appearance involving converging lines or the completed geometrical Form visible in an image.
The Dictionary therefore uses the broader principle:
Perspective = Method or Process + Resulting Image, View or Spatial Appearance.
Two Directional Classes of Perspective Method
Perspective methods can operate within either of the two principal directional classes of perspective.
- Viewing or Imaging Class: light, visual information or spatial data passes from an object, scene or existing image towards an eye, sensor, image plane or imaging system.
- Projecting Class: light, lines, images, shadows or spatial information are projected from a source, station point, projector, picture plane or representational system into physical, graphical, optical or simulated space.
Some Perspective Methods operate principally in one direction, while others combine or chain both directions.
Perspective Methods — Master Classification
The Dictionary groups Perspective Methods into eight principal operational families:
- 1. Direct-Observation and Tracing Methods
- 2. Instrument Viewing and Imaging Methods
- 3. Central-Projection Graphical Methods
- 4. Parallel-Projection Graphical Methods
- 5. Ground-Grid and Recession Methods
- 6. Measurement, Subdivision and Repetition Methods
- 7. Shortcut, Modular and Freehand Methods
- 8. Digital and Computational Methods
These families overlap. A single working procedure can employ several Perspective Methods in combination.
1. Direct-Observation and Tracing Methods
Direct-Observation and Tracing Methods record the apparent position, size, shape or direction of objects by observing them through, or in relation to, a fixed picture plane.
Examples include:
- the Perspective Window;
- veil or net methods;
- sighting grids;
- string methods;
- spider-line methods;
- mechanical perspectographs; and
- pencil-sighting methods.
These methods establish a controlled relationship between the observer, spatial object and picture surface so that the apparent scene can be recorded systematically.
The Perspective-Window Method
In the Perspective-Window, Veil or Net Method, a transparent or gridded picture plane is positioned between the observer and the spatial scene.
The observer views the scene from a fixed eye point and records where the apparent outlines of Forms intersect the picture plane or its grid.
Fixing the station point, Direction of Vision and picture plane stabilises the geometrical relationship while the image is being recorded.
String and Spider-Line Methods
In a String or Spider-Line Method, a taut string or equivalent visual ray extends from a fixed eye point towards a selected point on an object.
The intersection of that direction with a frame or picture plane is then marked and transferred to the drawing.
Mechanical forms of the method can use threads, pointers, sliding elements or articulated mechanisms to establish corresponding projected positions.
Mechanical Perspective Methods
A Mechanical Perspectograph constrains the relationships between eye point, object point and image point so that selected positions can be transferred systematically onto a drawing surface.
Historical Perspective Machines have employed frames, strings, pointers, grids, linkages and tracing mechanisms to assist the production of perspective images.
Pencil-Sighting Method
The Pencil-Sighting Method is a direct observational procedure in which an artist uses a pencil, ruler, proportional divider or similar object to compare apparent angles, alignments and relative dimensions.
The observed relationships are transferred proportionally to the drawing rather than being derived from a complete geometrical projection construction.
Perspective Checking Methods
Some Perspective Methods are used primarily for checking rather than generating the original image.
A mirror, for example, can display a drawing in reversed or altered form, helping reveal errors of alignment, proportion, balance or perspective that may be difficult to recognise in the original view.
The checking operation is therefore itself a Perspective Method even though it does not constitute the principal construction procedure.
2. Instrument Viewing and Imaging Methods
Instrument Viewing and Imaging Methods form, capture, magnify, reduce, transmit or otherwise modify a perspective image through an optical or imaging instrument.
Examples include:
- pinhole cameras;
- camera obscuras;
- photographic cameras;
- digital cameras;
- telescopes;
- microscopes;
- binocular instruments;
- scanners;
- range-imaging systems; and
- camera-display or camera-projector systems.
These methods principally belong to the Viewing or Imaging Class, although complete instrument systems may subsequently project, transmit or display the resulting image and therefore chain both directional classes.
The Human Eye and Perspective Method
The Dictionary distinguishes the human eye from an artificial perspective instrument.
The eye is the natural visual organ through which Visual Perspective Type 2 is experienced. Artificial optical instruments can nevertheless imitate, extend, magnify, reduce, record or transform some functions associated with natural vision.
Perspective methods can therefore arise through natural visual processes as well as through deliberately constructed graphical, optical and computational procedures.
3. Central-Projection Graphical Methods
Central-Projection Graphical Methods construct a perspective image by projecting selected spatial points or lines from a fixed station point or centre of projection towards a picture plane.
The intersections of these projectors with the picture plane establish the corresponding image points.
Central projection provides the general geometrical principle underlying ordinary One-, Two- and Three-Point Linear Perspective, but these point classifications should not themselves be confused with complete construction methods.
One-, Two- and Three-Point Perspective Are Not Complete Methods
The Dictionary makes an important distinction: One-Point, Two-Point and Three-Point Perspective identify geometrical configurations or types of central projection rather than complete drawing methods in themselves.
Several different procedures can be used to construct the same point configuration.
A one-point image, for example, can be established through direct observation, a Perspective Window, plan-and-elevation construction, ground-grid construction, measuring points or digital modelling.
Central-Projection Method
In the general Central-Projection Method, a three-dimensional object or scene is related to a fixed centre of projection and picture plane.
Selected object points are projected towards the picture plane, and the intersections determine their corresponding positions in the perspective image.
The same underlying principle can be implemented through several graphical, mathematical, instrumental or computational methods.
Plan-and-Elevation or Direct-Projection Method
The Plan-and-Elevation or Direct-Projection Method is a precise graphical procedure in which spatial information from two or more orthographic views is transferred into a perspective drawing.
A plan establishes horizontal positions and depths, while an elevation or section supplies heights and other vertical dimensions.
The procedure establishes the station point, Direction of Vision, picture plane, ground line and horizon, projects required object positions to the picture plane and transfers corresponding heights into the final perspective construction.
The method can be used to produce One-, Two- or Three-Point Perspective.
Common One-, Two- and Three-Point Methods
The Dictionary identifies several related graphical procedures, including:
- One-Point Common Method;
- Offset One-Point Method;
- Two-Point Common Method;
- Interior Two-Point Common Method; and
- Three-Point Common Method.
These names describe particular construction procedures rather than redefining the general geometrical principles of One-, Two- or Three-Point Perspective.
4. Parallel-Projection Graphical Methods
Parallel-Projection Methods employ projectors that remain parallel rather than converging at a finite station point.
These methods are particularly useful where dimensional, parallel or constructional information is more important than reproducing the appearance associated with a single finite viewpoint.
The principal families include Orthographic Projection and Oblique Projection.
Orthographic and Axonometric Methods
In Orthographic Projection, the projectors are perpendicular to the projection plane.
Important forms include:
- Multiview Orthographic Projection;
- plan, elevation and side views;
- first-angle and third-angle arrangements;
- Axonometric Projection;
- Isometric Projection;
- Dimetric Projection; and
- Trimetric Projection.
These methods preserve selected parallel and dimensional relationships in ways fundamentally different from central projection from a finite viewpoint.
Oblique-Projection Methods
In Oblique Projection, the parallel projectors are inclined relative to the projection plane.
The Dictionary identifies forms including:
- Cavalier Perspective;
- Cabinet Perspective;
- Military Perspective; and
- General Oblique Projection.
Parallel-projection methods should not be confused with the use of plans and elevations as source information for a central-perspective construction. These are different geometrical and operational relationships.
5. Historical Ground-Grid and Recession Methods
Ground-Grid and Recession Methods are used principally to construct the apparent diminution and spacing of horizontal planes, pavements, grids or repeated intervals extending through depth.
Important examples include:
- Alberti’s Legitimate Construction;
- Distance-Point Method;
- Bifocal Method;
- Diagonal Ground-Grid Methods; and
- Proportional-Recession Methods.
Alberti’s Legitimate Construction
Alberti’s Legitimate Construction is a historical One-Point Central Perspective method for constructing a foreshortened ground grid.
A rectangular picture field is divided along its ground line, orthogonals are directed towards the centric point and a separate lateral or sectional construction establishes the progressively diminishing spacing of the transverse lines.
The resulting construction produces a regular ground-plane grid viewed from a fixed station point.
The auxiliary points used in the procedure do not make the image Multi-Point Perspective: its principal configuration remains One-Point Central Perspective.
Distance-Point or Bifocal Method
The Distance-Point Method uses one or two distance points on the horizon to establish the diminishing depth of equal intervals or a square ground grid.
In a frontal one-point arrangement, these points correspond to horizontal ground-plane directions running at 45 degrees to the principal direction.
When corresponding left and right distance points are used, the construction has sometimes been called a Bifocal Method.
Piero della Francesca’s Perspective Methods
Piero della Francesca systematised mathematical perspective through procedures involving geometrical projection, proportional diminution and the transfer of information from plans, elevations and other auxiliary constructions.
The Dictionary cautions against reducing Piero’s work to one universal construction. His procedures extend from basic ground-plane problems to complex three-dimensional Forms including architecture, polyhedra and the human head.
6. Measurement, Subdivision and Repetition Methods
Measurement, Subdivision and Repetition Methods transfer known dimensions into perspective, locate intermediate divisions, establish the perspective centre of a plane, repeat modules and determine the apparent dimensions of objects at different depths.
Important methods include:
- Measuring-Point Method;
- Measuring-Line or True-Length-Line Method;
- Diagonal Subdivision;
- Fractional Subdivision;
- Scale-Figure or True-Height Method; and
- Reduced or Vanishing-Triangle Method.
Measuring-Point Method
The Measuring-Point Method transfers known dimensions from a measuring line into a receding direction.
A measuring point is geometrically related to the relevant vanishing point and station-point arrangement. Lines drawn towards it allow true intervals to be transferred into perspective.
The method can be used to construct measured floor grids, architectural bays, windows, columns, cubes and other repeated intervals.
Measuring-Line Method
A Measuring Line lies in the picture plane, or in another plane possessing a defined scale, so that dimensions can be marked without perspective foreshortening.
Those dimensions can then be projected into depth by means of vanishing points, measuring points, diagonals or other construction lines.
Vertical measuring lines can transfer heights, while horizontal measuring lines can establish widths or ground-plane distances.
Diagonal and Fractional Subdivision
A rectangular plane represented in perspective can be subdivided through its diagonals.
The intersection of the diagonals represents the projected centre of the original rectangular plane. Repeated diagonals can then generate halves, quarters, eighths and other regular subdivisions.
The method is useful for dividing walls, floors and façades, locating centred features, repeating architectural modules and constructing perspective grids.
Scale-Figure or True-Height Method
The Scale-Figure or True-Height Method uses a figure, post or measuring line of known height to establish the corresponding apparent height of equal Forms positioned at different depths.
Lines extending from the top and bottom of the known height towards the appropriate vanishing point establish a diminishing interval through which equivalent heights can be located.
Reduced or Vanishing-Triangle Method
When a required vanishing or measuring point lies too far outside the available drawing surface, a reduced geometrically similar triangle can be constructed within the working area.
Corresponding proportional directions and intervals can then be transferred into the principal drawing.
The Dictionary treats this as a family of reduced-construction procedures rather than one universally standardised method.
7. Shortcut, Modular and Freehand Methods
Shortcut, Modular and Freehand Methods reduce the number or extent of formal construction lines, work from an established perspective module, or estimate perspective relationships directly.
Examples include:
- One-Point Magic Method;
- Two-Point Magic Method;
- Super-Cube Method;
- Modular-Grid Construction; and
- Freehand Sighting.
These are practical methods of constructing or estimating perspective, not additional Perspective Classes.
Modular Perspective Methods
A modular method establishes a measured perspective cube, grid or other three-dimensional unit and uses it as a framework from which more complex Forms are developed.
The initial module can be subdivided, repeated, multiplied or expanded to organise larger spatial objects and environments.
This provides an efficient alternative to projecting every object point independently from a complete plan and elevation.
Freehand and Estimated Perspective
Freehand Perspective establishes the broad geometrical and proportional relationships of a scene through observation and estimation rather than complete measured construction.
An artist can estimate:
- the horizon;
- principal directions;
- vanishing-point positions;
- angles;
- depths;
- intervals; and
- relative proportions.
Pencil sighting, comparative measurement, simplified grids, diagonals and scale figures can support the process.
The Dictionary cautions that a visually convincing freehand image is not necessarily geometrically exact, although full measured construction is not required for every representational purpose.
8. Digital and Computational Methods
Digital and Computational Perspective Methods generate, reconstruct, measure, analyse, match or transform perspective through computer graphics and related computational procedures.
These methods include:
- three-dimensional computer modelling;
- virtual cameras;
- digital perspective grids and guides;
- vanishing-point tools;
- camera calibration;
- Perspective Matching;
- photogrammetry;
- Computer Vision; and
- digital image transformation.
Digital Three-Dimensional Method
In a Digital Three-Dimensional Method, a spatial model is constructed within a coordinate-based digital object space and viewed through a virtual camera.
The computer calculates the resulting projection according to variables including:
- camera position;
- Direction of Vision;
- Field of View;
- projection type; and
- image-plane settings.
The same model can subsequently generate multiple perspective views without requiring the object to be reconstructed for each new viewpoint.
Examples include CAD, CGI, game-engine, architectural-visualisation and Virtual Reality systems.
Two-Dimensional Digital Perspective Methods
Digital perspective methods do not necessarily require a complete three-dimensional model.
Two-dimensional drawing and image-editing systems can provide:
- perspective grids;
- perspective rulers;
- vanishing-point guides;
- transformation tools; and
- perspective-warp operations.
These tools can assist with construction, transformation or correction of an existing two-dimensional image without reconstructing the complete original object space.
Perspective Matching and Camera Calibration
Perspective Matching works in the reverse direction from ordinary image construction.
An existing photograph or image can be analysed to estimate properties such as:
- the horizon;
- vanishing points;
- Field of View;
- camera orientation; and
- camera position.
A digital model or additional image element can then be aligned with the recovered perspective relationships.
Photogrammetry and Computer Vision can extend this process by using several images to reconstruct aspects of three-dimensional geometry.
Perspective Methods Can Overlap
The eight families in the Master Classification are not rigidly isolated.
A Plan-and-Elevation construction may simultaneously employ:
- Central Projection;
- Measuring Points;
- Diagonal Subdivision;
- a modular grid; and
- digital drawing tools.
The complete workflow can therefore contain several Perspective Methods while still producing one unified perspective image.
Perspective Method and Category Overloading
A single Perspective Method can also belong legitimately to more than one top-level perspective category.
Linear Perspective provides a clear example. It can be mathematical because it follows geometrical relationships, graphical because it can be constructed as a drawing and New Media when its projection is calculated digitally.
Perspective Category Theory describes such legitimate membership in several categories as Category Overloading.
Perspective Method and Category Chaining
Different Perspective Methods can also operate sequentially.
A physical scene might first undergo optical and instrument imaging, then digital processing, then projection or screen display and finally human visual perception.
When several perspective categories operate sequentially in forming, processing, displaying or viewing an image, the Dictionary describes the process as Category Chaining.
Perspective Method and Composite Perspective
Several Perspective Methods can also operate together to produce a Composite Perspective.
A cinematic image, for example, can combine a physical scene, optical camera imaging, graphical or simulated Perspective Methods, digital processing and computer-generated imagery.
The resulting image or system should therefore not necessarily be attributed to one isolated method.
Perspective Method and Perspective System
A Perspective System is broader than an individual Perspective Method.
Volume 1 describes a Perspective System as a scheme of visual or optical perspective operating as a unit for image making, image projection, analysis or matching.
A system may contain one or more perspective categories, types, principles and methods.
A Perspective Method is therefore one operational component that may function within a larger Perspective System.
Perspective Machines and Perspective Methods
Perspective instruments and machines provide physical means through which particular Perspective Methods can be carried out.
The Dictionary groups Perspective Machines according to functions including:
- image capture;
- drawing and graphical construction;
- measurement;
- modelling; and
- illusion or immersion.
An instrument should therefore not automatically be equated with the Perspective Method itself: the machine provides the apparatus through which one or more methods can operate.
Perspective Methods Have Different Goals
Perspective Methods can be employed for different functions or goals, including:
- viewing;
- imaging;
- projecting;
- measuring;
- matching;
- representing;
- modelling;
- creating illusion; and
- producing immersion.
These functions should not be mistaken for additional basic Perspective Classes. The same method or system may pursue several goals simultaneously.
Natural and Artificial Perspective Methods
Perspective processes can occur naturally or through deliberately constructed methods.
Natural and visual processes include the optical and perceptual operations through which spatial reality forms a visible appearance.
Artificial Perspective Methods include mathematical, graphical, instrument, simulated and computational procedures devised to capture, calculate, construct, transform or represent corresponding spatial appearances.
Choosing a Perspective Method
No single Perspective Method is appropriate for every perspective problem.
The method selected depends upon what is being attempted: direct observation, image capture, geometrical construction, dimensional measurement, repeated subdivision, technical representation, digital modelling, image matching or another perspective function.
A highly measured architectural construction may require a different method from a rapid freehand drawing, a photograph, a computer-generated model or an optical measurement.
Historical and Modern Perspective Methods
The development of perspective has produced a large family of methods rather than the replacement of one old procedure by one new procedure.
Historical methods such as the Perspective Window, Alberti’s Legitimate Construction, Distance-Point Method and measuring procedures remain geometrically relevant, while modern systems can automate or extend many of the same relationships through CAD, CGI, virtual cameras, photogrammetry and Computer Vision.
Computer Perspective therefore expands the range of available Perspective Methods without eliminating the principles underlying earlier graphical or optical procedures.
Common Misconceptions about Perspective Methods
- Perspective is not one method. It is a broad field containing many visual, optical, mathematical, graphical, instrument, simulated and computational procedures.
- Perspective Method is not the same as Perspective Form. The method is the procedure; the Form is the resulting appearance.
- Perspective Method is not identical to Perspective Category. A category identifies the principal source or mode of the process; a method describes how the operation is performed.
- Perspective Method is not identical to Perspective Class. Class concerns the direction of operation: Viewing or Imaging, or Projecting.
- Perspective Type and Perspective Method can overlap without being identical. A type may identify a particular method, system, process or subdivision.
- One-, Two- and Three-Point Perspective are not by themselves complete drawing methods. They describe geometrical configurations that can be produced using several different methods.
- Linear Perspective is not the only Perspective Method. Optical imaging, parallel projection, direct observation, measurement and computational processes are also perspective methods.
- A Perspective Method does not have to involve vanishing points. Parallel Projection Methods, instrument imaging and other perspective procedures can operate differently.
- A Perspective Method does not have to be graphical. It can be optical, mathematical, instrumental, physical or computational.
- An instrument is not necessarily the same thing as a method. An instrument provides apparatus through which one or more Perspective Methods can operate.
- Several Perspective Methods can operate within one workflow. The Master Classification families deliberately overlap.
- Older Perspective Methods are not necessarily obsolete. Modern digital systems can implement, automate or combine many of the same geometrical principles.
- Freehand Perspective is not automatically geometrically exact. It is an estimated method that can nevertheless provide an effective spatial representation where full measured construction is unnecessary.
- A Perspective Method can operate within several categories. Mathematical, Graphical, Instrument and New Media Perspective can overlap within a single procedure.
Why Perspective Method Matters
Perspective Method matters because understanding perspective requires more than recognising the appearance of a completed image. It requires understanding how that image, view, measurement or spatial representation was produced.
Two perspective images can possess similar visible Forms while being produced by entirely different methods. A scene might be observed directly through a Perspective Window, constructed geometrically, captured by a camera, generated from a digital 3-D model or reconstructed from existing images.
Conversely, the same Perspective Method can be adapted to produce several different perspective configurations or Forms.
The concept of Perspective Method therefore connects theoretical perspective principles with the practical operations used in vision, optics, drawing, painting, photography, architecture, engineering, measurement, computer graphics and digital imaging.
Understanding Perspective Method provides a foundation for understanding Perspective Principle, Perspective System, Perspective Category, Perspective Class, Perspective Type, Perspective Form, Viewing or Imaging Perspective, Projecting Perspective, Direct-Observation Methods, Perspective-Window Methods, Instrument Perspective, Central Projection, Parallel Projection, Linear Perspective, Plan-and-Elevation Perspective, Ground-Grid Methods, Measuring-Point Methods, Subdivision Methods, Freehand Perspective, Digital Perspective, Computer Perspective, Perspective Matching, Photogrammetry, Computer Vision, Category Overloading, Category Chaining and Composite Perspective.
Explore Theory
Explore the principal theories, classifications, types, forms, geometries, spatial concepts and visual phenomena of perspective.
Theory Hubs
Foundations of Perspective Theory · Perspective Category Theory & Classification · Perspective Types and Forms · Perspective Geometry & Projection · Vanishing, Horizons & Directional Reference · Form, Space & Perspective Images · Perspective Phenomena, Vision & Problems · Advanced & Additional Perspective Concepts
Foundations & Classification
Theory of Perspective · Functions of Perspective · Perspective Process · Perspective Principle · Perspective System · Perspective Category Theory · Perspective Category · Perspective Type · Categorical Ambiguity · Combined Perspective
Perspective Types & Forms
Types of Perspective · Central Perspective · Parallel Perspective · Linear Perspective · Curvilinear Perspective · Axonometric Perspective · Camera Perspective · Digital Perspective · Artificial Perspective · 360-Degree Perspective · Panoramic Perspective
Geometry, Vanishing & Spatial Reference
Perspective Projection · Perspective Geometry · Projective Transformation · Picture Plane · Station Point · Vanishing Point · Horizon Line · Viewpoint · Vanishing Structures · Optical Versus Geometrical Vanishing
Form, Space & Perspective Images
Perspective and 3-D Space · Object Space · Image Space · Perspective Image / View · Optical Image Chain · Linear Perspective Images · Perspective Product
Vision, Phenomena & Problems
Perspective Phenomena · Foreshortening · Depth Cues · Field of View · Binocular Vision · Scale–Shape–Size Problem · Equivalence / Correspondence Problem · Perspective and Illusion · Perspective and Spatial Immersion
Further reference:
Dictionary of Perspective ·
Perspective Research Centre