Blended Perspective

Blended Perspective is a perspective form in which two or more scene geometries, image geometries or views are combined within one resulting view.

Within the terminology of Perspective Category Theory (PCT), two principal forms are distinguished:

Blended Scene Perspective — two or more separate spatial geometries are made to appear as one coherent spatial scene;
Blended Image Perspective — several images or views are blended or merged into one resulting image or view.

The essential principle is therefore one of spatial or image integration. What begins as several separately organised scenes, spaces or views is presented as a single resulting perspective.

Blended Perspective within Perspective Category Theory

Blended Perspective describes the organisation of the scene or image geometry within a resulting perspective view.

It should therefore be distinguished from classifications concerned with the source, direction or production process of perspective.

A blended view may be produced through Natural, Graphical, Optical, Instrument, Simulated or New Media processes. It may also participate in Composite, Synthetic or Combined Perspective.

What defines Blended Perspective is the fact that more than one scene geometry, image geometry or view has been brought into one resulting perspective.

Ordinary and Blended Perspective

Two broad scene-perspective forms can be distinguished: Ordinary Perspective and Blended Perspective.

Ordinary Scene Perspective concerns a single geometrically coherent scene. The scene may be viewed directly or represented in a photograph, drawing, film or digital image. Its defining feature is the coherence of its scene geometry.

Blended Perspective, by contrast, combines two or more scene or image geometries within one resulting view.

The distinction can therefore be summarised as:

Ordinary Perspective → one coherent scene geometry
Blended Perspective → two or more scene or image geometries combined

1. Blended Scene Perspective

Blended Scene Perspective, also described as a form of multi-scene perspective, occurs when a spatial view contains two or more separately scaled or structured spatial geometries that are made to appear as one integrated scene.

The resulting scene may appear to possess a homogeneous or single-scale geometry even though its constituent spaces actually possess different scales, structures or spatial organisations.

The basic relationship can be represented as:

Scene Geometry A + Scene Geometry B → apparently unified Scene Geometry

The viewer may therefore perceive one continuous space even though the underlying physical or represented scene contains more than one spatial geometry.

Multi-scene transformed into single-scene

Blended Scene Perspective can be understood as a transformation from a multi-scene structure into an apparent single-scene structure.

The constituent scene spaces may differ in:

scale;
depth;
spacing;
shape;
position;
orientation; or
perspective geometry.

These differences are coordinated so that, from the intended viewpoint, the scene appears to possess one continuous spatial organisation.

The apparent unity may therefore conceal substantial differences in the actual geometry of the component spaces.

The importance of viewpoint

Blended Scene Perspective is often dependent upon a restricted or particular viewpoint.

From the intended viewing position, differently organised spatial components can align so that their boundaries or differences become difficult to detect. The resulting view appears geometrically coherent.

If the observer moves substantially away from this position, however, the geometrical differences between the component spaces may become visible and the illusion may break down.

The successful blending of several spatial geometries may therefore depend upon the precise relationship between:

observer position;
viewing direction;
object position;
scale;
scene geometry; and
the perspective process used to form the view.

Blended Perspective and the Ames Room

The Ames Room provides an important example of the principles involved in Blended Scene Perspective.

The physical room is deliberately distorted rather than possessing the regular geometry that the observer assumes. From the controlled viewpoint, however, the room appears to possess a more ordinary spatial form.

People standing in different parts of the room can consequently appear to differ dramatically in size.

The apparent scene therefore presents a coherent spatial arrangement while the underlying physical geometry has been deliberately altered.

This illustrates a central feature of Blended Perspective: the apparent geometry of the viewed scene need not correspond directly to the actual geometry of its constituent spaces.

Accelerated and Decelerated Perspective

Blended Scene Perspective may employ Accelerated Perspective and Decelerated Perspective to coordinate differently scaled or structured parts of a scene.

Accelerated Perspective increases apparent recession or convergence, while Decelerated Perspective produces the reverse effect.

By applying such spatial transformations to different parts of a scene, otherwise incompatible geometries can be made to appear continuous from a selected viewpoint.

A blended scene can therefore contain spatial regions whose actual geometry differs significantly while their apparent perspective relationships are coordinated visually.

Blended Perspective and Forced Perspective

Forced Perspective is closely related to many forms of Blended Scene Perspective.

Forced Perspective deliberately alters the scale, spacing, position or geometry of physical objects or scene structures so that their apparent size, depth or distance differs from their actual physical arrangement.

When two or more differently structured regions of space are coordinated in this way and made to appear as one scene, the resulting view may constitute Blended Perspective.

For example, objects at different physical scales or distances may be arranged so that they appear to occupy a common spatial environment.

The scene is therefore both simulated in its deliberately altered physical construction and blended in the relationship between its different spatial geometries.

Blended Perspective and Double Perspective

Double Perspective is closely associated with Blended Perspective when two distinct perspective spaces are combined into an apparently unified scene.

Two separately organised spatial geometries may be visually conjoined so that they appear to belong to the same physical or represented environment.

The term Blended (Double) Perspective therefore emphasises the presence of multiple underlying perspective structures within one apparent view.

More complex forms may contain more than two component scene or image geometries, so the underlying principle extends beyond strictly double arrangements.

2. Blended Image Perspective

Blended Image Perspective concerns the second principal form of Blended Perspective.

Instead of combining different physical or simulated scene geometries, several images or views of a spatial scene are blended or merged into one image or view.

The relationship can therefore be represented as:

View A + View B + View C → single blended image or view

This is sometimes described as a transformation from multi-view to single-view.

The source views may have been recorded from different positions, at different times, through different instruments or using different imaging processes.

Multi-view transformed into single-view

Blended Image Perspective provides a way of combining information contained in several individual perspective images.

The resulting image may contain a wider, more complete or differently organised representation of spatial reality than any one of its constituent views.

Processes capable of producing such imagery include:

image processing;
multi-view imaging;
satellite imaging;
photogrammetry;
point-cloud generation;
image stitching; and
other forms of computational image integration.

The individual views may remain partly detectable, or the blending process may produce an apparently continuous single image space.

Blended Scene and Blended Image Perspective

The two principal forms of Blended Perspective therefore operate at different levels.

Blended Scene Perspective combines different spatial geometries.

Blended Image Perspective combines different images or views.

The distinction can be stated simply:

Blended Scene Perspective = multi-scene → apparent single-scene
Blended Image Perspective = multi-view → single image/view

A complex imaging system may potentially involve both. Several differently structured spaces may first be combined within a scene, and several views of that scene may subsequently be merged into one image.

Blended Perspective and Combined Perspective

Combined Perspective and Blended Perspective are related but not synonymous.

Combined Perspective is the broader intentional joining of two or more distinct views, images, methods or perspective spaces within one presented view or image.

Blended Perspective concerns the more specific situation in which multiple scene or image geometries are integrated into a resulting scene or view.

The distinction can therefore be expressed as:

Combined Perspective → distinct components intentionally brought together
Blended Perspective → their scene or image geometries integrated into one resulting view

A Combined Perspective may retain visibly distinct components, whereas a Blended Scene Perspective normally aims to make its constituent spaces appear continuous or geometrically unified.

Blended Perspective and Synthetic Perspective

Synthetic Perspective describes the unified visual or perceptual result produced when several perspective categories or processes combine.

Blended Perspective instead identifies a particular organisation of scene or image geometry.

A Blended Perspective may therefore also be Synthetic when its separate spatial or image components produce a perceptually unified result.

For example, two differently scaled scene geometries may be physically or graphically combined and then viewed optically as one continuous space.

In such a case:

Blended Perspective describes the integration of the geometries.

Synthetic Perspective describes the unified visual outcome.

Blended Perspective and Composite Perspective

Composite Perspective identifies a multi-category perspective process, system, image or environment produced when several Perspective Categories operate in sequence or combination.

Blended Perspective does not require its defining distinction to be made at the Category level. Its principal concern is the integration of multiple scene or image geometries.

A Blended Perspective system may nevertheless be Composite if, for example, its production combines Simulated, Optical, Instrument and New Media Perspective.

The two concepts therefore describe different aspects of the same potentially complex system:

Composite Perspective → categorical organisation
Blended Perspective → scene or image geometrical organisation

Blended Perspective in cinema and visual effects

Blended Perspective has important applications in cinema and visual effects because filmmakers frequently need separately produced spaces or images to appear as one scene.

Possible methods include:

Forced Perspective;
scaled scenery;
matte backgrounds;
front or rear projection;
optical compositing;
digital compositing;
computer-generated imagery; and
virtual production.

A foreground and background may occupy different scales or originate through different processes but be coordinated from the camera viewpoint so that the finished image appears spatially continuous.

The apparent scene can therefore possess a unity that does not exist in its underlying physical or represented construction.

Blended Perspective in New Media

New Media systems greatly extend the possibilities of Blended Perspective because digital processes can merge physical, represented and computational spaces.

Computer-generated imagery, visual effects, augmented reality and virtual production can combine several visual layers or scene geometries within one apparent spatial environment.

Different views may also be computationally aligned and merged to produce panoramic, photogrammetric or three-dimensional representations.

Blended Perspective is therefore relevant both to the construction of hybrid spatial scenes and to the computational merging of multiple images or viewpoints.

Apparent and actual spatial geometry

Blended Scene Perspective demonstrates an important distinction between actual geometry and apparent geometry.

The actual scene may contain several separately scaled or structured spatial regions.

The perspective process can nevertheless cause the observer to perceive these regions as a single homogeneous or single-scale space.

Thus:

actual space → multiple geometries
apparent view → one integrated geometry

This difference between the physical arrangement and its apparent perspective structure makes Blended Perspective particularly important in the analysis of visual illusion, simulation and spatial representation.

Why Blended Perspective matters

Many perspective images and spatial illusions cannot be adequately described as views of one geometrically uniform scene.

They may instead bring together several differently organised spaces or multiple views and present them as one resulting perspective.

The concept of Blended Perspective makes it possible to distinguish:

a single coherent scene from a multi-scene construction;
actual spatial geometry from apparent spatial geometry;
multi-scene from apparent single-scene perspective;
multi-view from single-image perspective;
Blended Scene Perspective from Blended Image Perspective; and
geometrical blending from the broader processes identified by Composite, Combined and Synthetic Perspective.

Blended Perspective is therefore an important perspective form because it identifies the integration of two or more scene or image geometries within one resulting perspective view.