Glossary

Cubic

A projection which represents the view around the observer as six faces of a cube in which the observer is at the center. Cubic panoramas are capable of showing the view all around the observer, including straight up and straight down, in very high quality. This is the form of projection used in the most recent versions of QuickTime VR and has been traditionally used in VRML scenes, background environments in action games, and other 3D technologies.

Cylindrical

A projection which represents the view from the observer on a cylinder of varying height and field of view. Cylindrical panoramas do not show the view straight up or straight down. This was the form of projection used in the first versions of QuickTime VR, and is what most users of the QuickTime VR Authoring Studio (QTVRAS) are familiar with.

Equirectangular

A projection which represents the surface of a sphere as a flat rectangle. An equirectangular image has the horizontal circumference of the sphere's equator as the width, and half the sphere's vertical circumference (a line of longitude) as the height. Equirects are thus exactly 2:1 in proportion, and must have these proportions to be correctly identified as equirectangular images. (Also called spherical by some stitcher programs.)

Historically, the projection is thought to have been invented by Marinus of Tyre in about AD 100, and though less suited to traditional geography because of its inherent distortions, it is very suitable for use in with computer based panoramic VR as it can be undistorted in real time with little effort.

Equirects are usually the format produced by panorama photographers who stitch using PanoTools or related programs, and either left in this format for showing as a PTViewer Java applet, or subsequently converted to another projection, eg, cubic, for use in QuickTime VR or other technologies.

Hotspot

A region of the panoramic image which, when clicked, links to somewhere else, such as another node in a multinode tour, or a URL to another web location altogether.

Multinode

Refers to having more than one node in a scene. A "multinode movie" contains more than just one location, allowing you to traverse locations and have a more complete experience of the photographed area.

Node

A 360° panorama showing a single physical location, the place where the panorama was originally photographed. The term is often used to refer to a single VR panorama.

Object VR

A different form of VR, though still represented on the computer screen and still consisting of photographs. Object VRs or "VR Objects" represent a physical object as seen from many sides. They are created either by taking photographs from many angles around the object, or through modeling the object in a 3D rendering program. Object VRs are different from panoramas in that they show the scene/object from the outside looking in, while panoramas show the view from inside the panorama looking out. Some VR technologies provide a means for creating both panoramas and objects and linking them together through hotspots.

OpenGL

"Open Graphics Libary" - an industry standard software-to-hardware interface for making use of the high performance 3D display capabilities of graphics cards present inside most current computers.

Panning

The process of moving a panoramic image around by dragging it with the mouse. In this context, "panning" refers to both horizontal and vertical movement, though the term "tilting" can also be used to specify just the vertical direction.

Panorama

Traditionally, a photograph showing a wide area. In multimedia software use, "panorama" usually refers to an image that moves as the user moves their mouse to show a realistic view of the area originally photographed, usually 360° around and a variable amount up and down. To distinguish these from the sorts of photographic panoramas shown in coffee table books, additional terms such as "immersive" or "VR" are often included to specify their interactive nature.

PanoTools

Comprehensive series of software tools created by mathematics professor and panorama expert Helmut Dersch. Included both standalone programs and Photoshop filters. Regarded by many professional photographers as very powerful, though somewhat difficult to use. Front-end programs such as PTGui (Windows) and PTMac (Mac OS X) provide a friendly interface to the core PanoTools functions.

Photographic VR

A term often used to describe the type of VR that is being shown, that is, VR displayed with a photo rather than through special goggles. "Photo VR" uses photographic techniques to prepare a usually seamless image (a panorama) which encompasses a large part of the area photographed. The result is usually displayed to the viewer in one of the interactive playback formats such as QuickTime VR, PTViewer, etc.

Projection

The process of representing a three dimensional object, such as a sphere, cylinder or cube, on a flat two dimensional space, such as a rectangular image or computer screen.

PTViewer

Java based panorama viewer included in the PanoTools package. Often used as the "everyone-will-be-able-to-view-this" solution for embedding panoramas in web pages.

QTVR

Shorthand for "QuickTime VR"

QuickTime VR

Refers to the software technologies introduced in 1995 to allow photographs to be joined in a seamless fashion to create a continuous panoramic image, then to manipulate this image in real-time to show a realistic viewpoint of the area originally photographed, with additional features such as hotspots linking the locations photographed.

The term "QuickTime VR" is mainly used to indicate a specific form of panoramic media which can be shown either by the QuickTime application, the QuickTime plugin in a web page, or other programs that work with the QuickTime VR format. Sometimes "QuickTime VR" is used in a general sense to talk about immersive panoramas that can be displayed on a computer.

In the photographic VR community, QuickTime VR is generally recognized as having the highest quality and most pleasing playback characteristics. It's chief drawback in the past, the lack of default installation on the majority of Windows PCs, has in recent times become much less of an issue given the favorable combination of:

• antitrust court settlement against Microsoft discouraging their anti-competitive behavior, which included "highjacking" media intended for non-Microsoft plugins,
• popularity of the iTunes software which itself requires and installs QuickTime, meaning vast numbers of web users have it available, and
• widespread prevalence of broadband internet access allowing for the download of either the 11MB installer if required, or the large high-resolution movies popular with QuickTime VR creators.

Resolution

The quality or detail available in a photographic image. Generally, panoramas are divided into high-resolution ("hi-res"), meaning a lot of detail is available but the size is large and slow to load, or low-resolution ("lo-res"), meaning the image may appear blurry and less distinct, but the size is small so it loads faster. Sometimes web site authors include both hi-res and lo-res versions of the same panorama to cater for both broadband/patient users and dial-up/impatient people.

Scene

Usually refers to a collection of nodes. For example, you may be viewing node 3 of a scene containing 7 nodes. Some VR technologies refer to a single node as a scene, so a term like "multinode tour" is usually less ambiguous.

Spherical

Relating to a sphere. Some stitchers use this term to refer to an image consisting of an equirectangular panorama.

Stitching

The process of joining smaller images into a larger, more encompassing panoramic image. Stitching programs usually overlap and merge the source photographs to create a seamless blend between them. Stitchers in common use include Realviz Stitcher, PTGui (Windows), PTMac (Mac OS), and various others. Older stitchers include Apple's QuickTime VR Authoring Studio.

Tilting

Moving a panoramic image up and down. When you "tilt" up, you look towards the sky, and when you tilt down, you look towards your feet.

Tour

A presentation of varying complexity aimed at revealing what a given area looks like. Tours usually have more than one node (see multinode) and may have other embellishments such as maps which show an overview of the area and sounds which play when the viewer enters certain parts.

URL

Uniform Resource Locator. An address for something on the internet, most commonly used to specify an address of a web page. Also known as a URI (Uniform Resource Indentifer).

VR

Acronym for Virtual Reality, a means of simulating reality using technology. In the context of panoramas, it refers to having an image manipulated in real-time to show an authentic viewpoint of the area originally photographed, then displayed on the viewer's two-dimensional computer screen. To distinguish its use from the technologies where a scene is projected into a special pair of goggles, the terms "photographic VR" or "VR panorama" are often used.

VRML

Virtual Reality Modeling Language. A specification for defining virtual worlds containing 3D objects and interactions. Some VR technologies extend it to use background textures to contain panoramic VR images.

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