- Annex Detail -

NTTC PRESENTATION


These slides were first seen at the 2019 NATO Training Technology Conference (NTTC) in Virginia Beach, USA. The presentation introduces designers and developers to "Omnidirectional Stereo Computer Generated Images (ODS CGI)", a method of making codeless, passive virtual reality experiences. See also the Case Study: ODS Images and Animation.

T.M.Wilcox, developer of instructional VR prototypes, explains Omni-Directional Stereo Computer Generated Images and Animation (ODS CGI). Mr. Wilcox has 30+ years experience in computer game design, software development, and 3D concept visualization.

The high cost of creating interactive, vector-based virtual reality experiences spurred development of less expensive, passively viewed alternatives. Passive virtual reality does not require game-world interaction design and development, or programming.

Passive virtual reality restricts users to a single viewpoint or predefined pathway. Interactive VR is vector-based and can offer free navigation of an extensive 3D world-space.

The advantages are that non-interactive, omni-directional stereo (ODS) VR content typically takes less time to produce, and can be viewed with less powerful headsets. Complex, interactive VR experiences may require powerful graphics adapters and workstation-class computers.

ODS images and animation are often computer generated like these frames from the ChemSim-VR Prototype. ODS still photography and video require precisely aligned dual cameras with wide angle, fish-eye lenses.

ODS CGI has some unusual production requirements. Developers often use movie and game industry software like 3DS Max and Unity. Game engines like Unity have characteristics making them especially suitable to creating ODS CGI.

3D models, lights, and cameras occupy a scene while motion paths control changes in their position and orientation. For each shot, developers choose a location viewpoint for the camera with an initial, targeted direction.

For each second of animation the whole environment is captured up to 120 times in 360 degrees as if filming with a spherical lens. Stereoscopic, 360 surround animation recorded at 120fps in 8k resolution produces exceptionally large video files.

The Unity game engine allows creative control of ODS frame export parameters with its Recorder plug-in. ODS frames are stored as high resolution equirectangular projections, like flattened maps of a globe.

Software on VR headsets prepares each frame for display by projecting them onto the inside surface of a virtual sphere, with the observer at the center. Deciding what’s important in a scene and placing it within a 180 degree field of view is a design option.

For 3D stereographic effect, Unity records an image for both eyes automatically with a separation value chosen by the developer. Too much stereo separation causes eye strain, too little and the stereographic benefit is lost.

This is the middle of an equirectangular projection. The closer the camera is to an object, the more pronounced the 3D stereographic effect. Too close and minor head movement makes it obvious there’s no lateral translation compensation or head tracking.

A stereographic image stacks a pair of offset views, the uppermost for the left eye, the lower for the right. Other stereo formats include Left/Right and Cubic while Equirectangular is arguably more versatile.

DemoSpheres are non-stereographic, 360 degree panoramic images originally developed for concept visualization with experimental head mounted displays. Popular 3D modeling and animation apps often include an option to export 360 panoramas.

Alongside their seminal research in ODS imaging technology, Google developed a product and process they call PhotoSpheres. PhotoSpheres use an equirectangular panorama with a Javascript wrapper and an XML setup file on a web page.

Using a VR headset, a 360 panoramic scene surrounds the observer whether or not the image is stereographic. Set designers, videographers, and film directors use game engines and VR headsets to pre-visualize dramatic scenes.

Immersive ODS computer generated images on VR headsets are a significant advance beyond two dimensional media. They can be highly detailed thanks to off-line rendering, making them ideal for instructional applications.

Remember, you can’t change your location within a 360 panorama or ODS CGI, or interact with objects in the scene as you can with vector-based virtual reality. But you can build compelling 3D VR presentations with readily available, detailed CAD models of almost anything.