Class
The two Classes may operate separately, sequentially or together.
Perspective Visual
Perspective Optical
Perspective Mathematical
Perspective Graphical
Perspective Instrument
Perspective Simulated
Perspective New Media
Perspective
A Perspective Class may operate within one or more Category modes.
The Projecting Class, or Projection Perspective, is one of the two fundamental directional Classes of perspective. It concerns processes in which light, radiation, an image, shadow, beam or related pattern is projected forwards into or across space.
In simplified form:
Light, radiation, image, shadow or beam → forwards into or across space
Projecting Class / Projection Perspective
The defining feature of the Projecting Class is direction. The perspective process proceeds forwards from a source, emitter, projector, illuminated object or other origin into or across spatial reality.
The Class is deliberately broader than geometrical projection or image projection alone. A projected Perspective Product may be a visual image, a pattern of light, an outline, a shadow, a beam or another spatially projected optical or electromagnetic effect.
Two Fundamental Directions
Perspective Category Theory distinguishes two basic directional Classes:
- Viewing or Imaging Class — object, scene or image → eye, sensor or imaging system.
- Projecting Class — light, radiation, image, shadow or beam → forwards into or across space.
The first describes a receiving or image-forming direction. The second describes a forward-projecting direction.
Projection Does Not Necessarily Mean Image Projection
In ordinary usage, the word projection is often associated with cinema, slide projectors or geometrical projection. Within the Projecting Class, however, projection is used in a broader directional sense.
A process can belong to the Projecting Class whenever light, radiation or another relevant pattern proceeds forwards into or across space. A complete pictorial image does not have to be projected.
Natural Projection
Projection can occur naturally. Sunlight travels forwards through space and illuminates objects, surfaces and environments. The resulting light and shadow relationships can reveal position, orientation, shape and spatial structure.
Natural projection therefore does not require a human-made projector or a geometrical construction.
Artificial Light Projection
Artificial illumination provides another straightforward example of the Projecting Class. A candle, lamp, spotlight, torch or laser emits or directs light forwards into space.
The resulting light may illuminate a scene, form shadows, reveal surfaces or create spatial patterns without necessarily forming a conventional projected image.
Image Projection
Image projection is one important special case of the Projecting Class. A cinema projector, slide projector or digital projector sends an already formed image forwards through space onto a screen or other receiving surface.
The resulting image can be considered a Projected Perspective Image. This contrasts with a Captured Perspective Image, formed through the opposite Viewing or Imaging direction.
Shadow Projection
Projected light can also produce shadows. When an object interrupts a light field, its spatial relationship to the source and receiving surface produces an outline or shadow pattern.
Shadow projection shows why the Projecting Class cannot be reduced simply to the projection of pictures. The projected outcome may instead be a spatially organised absence or reduction of light.
A Centre of Projection Is Not Required
The broad Projecting Class does not require every process to possess a single geometric centre of projection.
A source may be extended, diffuse, distributed or otherwise non-central. Sunlight is often treated approximately as parallel because of the very great distance of the Sun; diffuse illumination may arise from many spatial directions; and technical systems can project structured light without corresponding to a simple central-perspective construction.
Central projection is therefore an important geometrical case within the wider field of projection, not the definition of the entire Projecting Class.
Geometrical Projection
In graphical and mathematical perspective, geometrical projection establishes formal relationships between spatial objects and their projected representations.
Central projection uses projectors related to a fixed centre of projection. Parallel projection uses projectors that remain parallel. Orthographic, oblique, axonometric and other systems employ different geometrical conditions.
These geometrical systems are important Perspective Types or methods, but the Projecting Class itself remains the more fundamental directional classification.
Projection onto a Plane
Projection onto a two-dimensional plane is one major application of projection, but it should not be confused with the entire Projecting Class.
Graphical perspective may project spatial relationships onto a picture plane. Optical systems may project images onto screens or sensors. Other projection processes may operate through three-dimensional space without terminating on a single flat surface.
Captured and Projected Images
The distinction between the two Classes becomes especially clear when comparing Captured and Projected Perspective Images.
- Captured Perspective Image — formed in the Viewing or Imaging direction, from spatial reality towards an eye, camera, sensor or image plane.
- Projected Perspective Image — sent forwards from a projector or source into spatial reality or onto a receiving surface.
The same image can therefore participate in both Classes sequentially. A camera may first capture it, after which a projector displays it forwards onto a screen.
Projection Across the Electromagnetic Spectrum
The Projecting Class is not restricted conceptually to visible light. Technical perspective systems may employ other regions of the electromagnetic spectrum for illumination, sensing, ranging, imaging or spatial analysis.
The relevant principle remains directional: radiation is emitted or projected forwards into or across a spatial reality.
Projecting Class and Perspective Categories
Class and Category describe different properties of a perspective process.
A Category identifies a principal source or mode. A Class identifies the fundamental direction of operation.
A Projecting-Class process may therefore operate within Natural, Optical, Mathematical, Graphical, Instrument, Simulated or New Media Category modes, depending upon the particular system involved.
Why the Distinction Matters
Separating the Viewing or Imaging Class from the Projecting Class prevents several different processes from being treated as though they were the same.
A camera receives and forms an image; a projector sends an image forwards. An eye receives light; a lamp emits light. A shadow is produced through forward illumination; a photograph records incoming light.
These processes may work together within a single technical system, but their basic directional relationships remain analytically distinct.
Projecting Class Within the Analytical System
Within the PRC analytical framework, the Projecting Class belongs to the Class analytical level.
The seven principal analytical levels are:
Category · Class · Type · Form · Phenomenon · Function · Product
The Class level asks: in which fundamental direction does the perspective process operate? For the Projecting Class, the answer is forwards into or across space.
Related Perspective Topics
- Perspective Class
- Viewing or Imaging Class
- Perspective Category
- Optical Perspective
- Mathematical Perspective
- Graphical Perspective
- Instrument Perspective
- Perspective Image
- Perspective Product
- Abridged Dictionary of Perspective
Perspective Projection, in its broadest sense, belongs to the Projecting Class: one of the two fundamental directional Classes of perspective. It includes processes in which light, radiation, images, shadows, lines, beams or other structured information are projected forwards from a source or system into or across space.
Projection therefore does not necessarily require a picture plane, a projected image, or a centre of projection. Sunlight entering space, light radiating from a candle, a torch or spotlight beam, a cast shadow, cinema projection and digital projection mapping can all involve the projecting direction in different ways.
Source / system → light, image, shadow, beam or structured information → space
Projecting Class / Projection Perspective
The Projecting Class describes the outward or forward direction of a perspective process. Something originates at, passes through, or is controlled by a source or system and is projected into physical, optical, graphical or simulated space.
The thing projected may be extremely simple, such as light spreading from a candle, or highly structured, such as a moving cinematic image projected onto a screen. What defines the Class is primarily the direction of the process, rather than a particular device, geometry or type of image.
The Two Fundamental Directions of Perspective
The PRC distinguishes two fundamental directional Classes:
- Viewing or Imaging Class — light or visual information passes from an object, scene or existing image towards an eye, sensor, image plane or imaging system.
- Projecting Class — light, radiation, images, shadows, beams or other structured information are projected forwards from a source or system into or across space.
A perspective system may employ either Class independently, or may combine the two sequentially or simultaneously.
Projection Does Not Necessarily Mean Image Projection
The word projection is often understood too narrowly as the projection of a pre-existing image onto a screen. That is only one form of projection.
Within the broader Projecting Class, what is projected may include:
- light or other electromagnetic radiation;
- a beam or field of illumination;
- an image;
- a shadow or silhouette;
- lines or geometrically defined projectors;
- patterns or structured light;
- spatially organised graphical or digital information.
The output need not even constitute a recognisable image. A simple beam of light projected into physical space still exhibits the fundamental projecting direction.
Natural Projection
Projection is not necessarily artificial. Natural sources can project light and radiation through space.
- The Sun projects electromagnetic radiation through space; over the scale of ordinary terrestrial scenes its incoming rays can often be treated as approximately parallel.
- A candle or flame radiates light outward into the surrounding environment.
- Natural illumination can produce cast shadows when objects interrupt projected light.
These cases demonstrate why the Projecting Class cannot be defined only by cinema, graphical construction or central projection geometry.
Artificial Light Projection
Artificial sources provide equally clear examples of the projecting direction. A torch, spotlight, searchlight or other lighting system projects light forwards into physical space.
The projected light may form a narrow beam, a broad cone or field of illumination, or a more complex controlled distribution. The defining feature is not whether a picture is formed, but that radiation travels outwards from the source or system into the target space.
Image Projection
Image projection is an important but more specialised case of the Projecting Class. Here the outgoing light is structured so that an image is produced on or within a target surface or space.
Examples include:
- slide and photographic projection;
- cinema projection;
- video and digital projection;
- dome and panoramic projection;
- projection mapping onto buildings and three-dimensional surfaces;
- other optical or simulated image-projection systems.
In such cases the projector does more than illuminate the target: it projects spatially organised image information.
Shadow Projection
A shadow is another important projecting phenomenon. Light travels from a source into space, but an intervening object blocks part of that light. The resulting absence or reduction of illumination produces a projected shadow on another surface or within the surrounding spatial field.
Shadow projection therefore demonstrates that the Projecting Class is not restricted to the positive projection of luminous images. Object outlines, occlusions and interruptions of projected radiation can also generate perspective information.
A Centre of Projection Is Not Required
A centre of projection belongs to particular projection geometries, especially central or perspective projection. It is not a necessary condition of the Projecting Class itself.
Projecting processes may involve diverging, converging, approximately parallel, collimated, reflected, refracted, structured or simulated rays and beams. Different systems therefore require different geometrical descriptions.
Central projection is consequently one important type or geometrical arrangement of projection, not a definition of projection as a whole.
Geometrical Projection
In graphical and mathematical perspective, projection has a more specific geometrical meaning: spatial points, lines, surfaces or forms are related to another plane, surface or space by defined projectors, rays or mappings.
Such methods include both central projection and forms of parallel projection. Orthographic, axonometric and oblique systems therefore belong to projection geometry even though they do not operate through the same finite projection centre used in central linear perspective.
This geometrical meaning should be distinguished from the broader analytical meaning of the Projecting Class.
Projection onto a Plane
Projection onto a two-dimensional plane is one familiar geometrical case. Spatial information is transferred to a plane through a defined family of projectors or rays.
In central perspective projection, those projectors pass through a finite projection point. In parallel projection, the projectors remain parallel and no finite centre of projection is required.
Projection onto a plane is therefore a specialised construction within the much larger subject of projection.
Captured and Projected Images
The directional distinction becomes particularly clear when a camera and projector are compared.
- Camera: spatial reality → camera or sensor → captured image. This belongs to the Viewing or Imaging Class.
- Projector: image source → projector → projected light/image → screen or spatial environment. This belongs to the Projecting Class.
A cinema system can therefore contain both Classes in sequence: the scene is first captured through an imaging process and the resulting image is later projected back into physical space.
Projection Across the Electromagnetic Spectrum
The Projecting Class is not confined to visible light. Perspective processes may involve other forms of electromagnetic radiation where radiation is transmitted, directed, projected or used to obtain spatial information.
Depending on the particular system, this may include infrared, ultraviolet, X-rays, microwaves, radio waves or other wavelengths. The relevant perspective process may be natural, optical, instrumental, computational or simulated.
Projecting Class and Perspective Categories
The Projecting Class can operate within more than one perspective Category. A projecting process may be Natural, Optical, Graphical, Mathematical, Instrument, Simulated or New Media in character, depending on its source, method and medium.
These Categories describe how or where the perspective process operates. The Class identifies its fundamental directional behaviour.
Why the Distinction Matters
The term projection is used in optics, geometry, drawing, photography, cinema, computer graphics, lighting and many other fields, often with different meanings. Treating every projection as though it were central geometrical projection obscures these differences.
The Projecting Class provides the broader analytical framework. It identifies the common directional principle first; more specific projection systems, geometries and image forms can then be classified underneath it.
Related Perspective Topics
- Perspective Class
- Viewing or Imaging Class
- Perspective Direction
- Perspective Geometry
- Linear Perspective
- Parallel Perspective
- Orthographic Perspective
- Axonometric Perspective
- Oblique Perspective
- Stereographic Perspective
- Abridged Dictionary of Perspective
Explore Theory
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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