Nicolas S. Holliman

Controlling perceived depth in stereoscopic images.

Stereoscopic images are hard to get right, and comfortable images are often only produced after repeated trial and error. The main difficulty is controlling the stereoscopic camera parameters so that the viewer does not experience eye strain or double images from excessive perceived depth. Additionally, for head tracked displays, the perceived objects can distort as the viewer moves to look around the displayed scene. We describe a novel method for calculating stereoscopic camera parameters with the following contributions: (1) Provides the user intuitive controls related to easily measured physical values. (2) For head tracked displays; necessarily ensures that there is no depth distortion as the viewer moves. (3) Clearly separates the image capture camera/scene space from the image viewing viewer/display space. (4) Provides a transformation between these two spaces allowing precise control of the mapping of scene depth to perceived display depth. The new method is implemented as an API extension for use with OpenGL, a plug-in for 3D Studio Max and a control system for a stereoscopic digital camera. The result is stereoscopic images generated correctly at the first attempt, with precisely controlled perceived depth. A new analysis of the distortions introduced by different camera parameters was undertaken.

Three-Dimensional Displays: A Review and Applications Analysis

S. Benton published a definitive taxonomy of the first one hundred and seventy years of 3D displays covering the field up to the year 2000. In this article we review how display technologies have advanced in the last ten years and update Bentons taxonomy to include the latest additions. Our aim is to produce a display taxonomy suitable for content producers highlighting which displays have common requirements for image delivery. We also analyze key technical characteristics of 3D displays and use these characteristics to suggest the future applications for each category of display.

Mapping perceived depth to regions of interest in stereoscopic images

The usable perceived depth range of a stereoscopic 3D display is limited by human factors considerations to a defined range around the screen plane. There is therefore a need in stereoscopic image creation to map depth from the scene to a target display without exceeding these limits. Recent image capture methods provide precise control over this depth mapping but map a single range of scene depth as a whole and are unable to give preferential stereoscopic representation to a particular region of interest in the scene. A new approach to stereoscopic image creation is described that allows a defined region of interest in scene depth to have an improved perceived depth representation compared to other regions of the scene. For example in a game this may be the region of depth around a game character, or in a scientific visualization the region around a particular feature of interest. To realize this approach we present a novel algorithm for stereoscopic image capture and describe an implementation for the widely used ray-tracing package POV-Ray. Results demonstrate how this approach provides content creators with improved control over perceived depth representation in stereoscopic images.

Autostereoscopic 3D display systems with observer tracking

An analysis of the basic approaches to autostereoscopic 3D display is presented, together with a discussion of the application of liquid crystal displays (LCDs) in this field. We show that of particular importance in the design of such displays is the illumination optical system and the optical quality of viewing windows produced. The window illumination quality determines many performance criteria including image fidelity, cross talk, viewing freedom and observer dynamics in a wide range of displays. The effects of degradation in window structure are described. Recent progress in 3D systems incorporating two LCD panels based on bulk and micro-optic systems is described. Further a new single LCD flat panel display is described in which observer tracking can be achieved without a requirement for moving parts. We detail the modifications to the LCD pixel structure necessary and how tracking may be achieved by manipulating the video information presented to the display panel.

Observer-tracking autostereoscopic 3D display systems

This paper presents an examination of the requirements for observer tracking autostereoscopic 3D display systems. The optical requirements for the imaging of autostereoscopic viewing windows in order to maintain high image quality over a large range of observer positions are described. A number of novel displays based on LCD (liquid crystal display) technology have been developed and demonstrated at Sharp Laboratories of Europe Ltd (SLE). This includes an electronically switchable illuminator for the macro-optic twin-LCD display; and a compact micro-optic twin-LCD display which maintains image quality while extending display size and viewing freedom. Work has also been in progress with flat panel displays to improve window quality using a new arrangement of LCD pixels. This has led to a new means to track such a display with no moving parts.

Smoothing Region Boundaries in Variable Depth Mapping for Real Time Stereoscopic Images

We believe the need for stereoscopic image generation methods that allow simple, high quality content creation continues to be a key problem limiting the widespread up-take of 3D displays. We present new algorithms for creating real time stereoscopic images that provide increased control to content creators over the mapping of depth from scene to displayed image. Previously we described a Three Region, variable depth mapping, algorithm for stereoscopic image generation. This allows different regions within a scene to be represented by different ranges of perceived depth in the final image. An unresolved issue was that this approach can create a visible discontinuity for smooth objects crossing region boundaries. In this paper we describe two new Multi-Region algorithms to address this problem: boundary smoothing using additional sub-regions and scaling scene geometry to smoothly vary depth mapping. We present real time implementations of the Three-Region and the new Multi-Region algorithms for OpenGL to demonstrate the visual appearance of the results. We discuss the applicability and performance of each approach for rendering real time stereoscopic images and propose a simple modification to the standard graphics pipeline to better support these algorithms.

Describing the dimensionality of geospatial data in the earth sciences—Recommendations for nomenclature

Complications exist when describing the dimensionality of geoscientific data sets. One difficulty is that there are a number of different, valid ways to consider dimensionality. Unlike traditional methods of field data capture, modern digital methods typically record the position of every sample point relative to a three-dimensional (3D) coordinate system, even for simple measurement strategies such as 1D line sampling. Critically, the best way to describe the dimensionality of a data set will depend on the context in which the data are presented. Terms such as “2½D” are generally inappropriate for nonspecialist audiences. Because ambiguity and inconsistency are already widespread, it is usually advisable to explain clearly the nature of each data set, the method used to capture the data, and particularly whether data acquisition was restricted to the outcrop surface or includes sampling of the subsurface.

Stereoscopic game design and evaluation

We report on a new game design where the goal is to make the stereoscopic depth cue sufficiently critical to success that game play should become impossible without using a stereoscopic 3D (S3D) display and, at the same time, we investigate whether S3D game play is affected by screen size. Before we detail our new game design we review previously unreported results from our stereoscopic game research over the last ten years at the Durham Visualisation Laboratory. This demonstrates that game players can achieve significantly higher scores using S3D displays when depth judgements are an integral part of the game. Method: We design a game where almost all depth cues, apart from the binocular cue, are removed. The aim of the game is to steer a spaceship through a series of oncoming hoops where the viewpoint of the game player is from above, with the hoops moving right to left across the screen towards the spaceship, to play the game it is essential to make decisive depth judgments to steer the spaceship through each oncoming hoop. To confound these judgements we design altered depth cues, for example perspective is reduced as a cue by varying the hoops depth, radius and cross-sectional size. Results: Players were screened for stereoscopic vision, given a short practice session, and then played the game in both 2D and S3D modes on a seventeen inch desktop display, on average participants achieved a more than three times higher score in S3D than they achieved in 2D. The same experiment was repeated using a four metre S3D projection screen and similar results were found. Conclusions: Our conclusion is that games that use the binocular depth cue in decisive game judgements can benefit significantly from using an S3D display. Based on both our current and previous results we additionally conclude that display size, from cell-phone, to desktop, to projection display does not adversely affect player performance.

Investigating the performance of path-searching tasks in depth on multiview displays

Multiview auto-stereoscopic displays support both stereopsis and head motion parallax depth cues and could be superior for certain tasks. Previous work suggests that a high viewpoint density (100 views/10cm at the eye) is required to convincingly support motion parallax. However, it remains unclear how viewpoint density affects task performance, and this factor is critical in determining display and system design requirements. Therefore, we present a simulated multiview display apparatus to undertake experiments using a path-searching task in which we control two independent variables: the stereoscopic depth and the viewpoint density. In the first experiment, we varied both cues and found that even small amounts of stereo depth (2cm) reliably improved task accuracy and reduced latency, whereas there was no evidence of dependence on viewpoint density. In the second experiment, we switched off the stereoscopic cue and varied viewpoint density alone. We found that for these monoscopic images increasing viewpoint density resulted in some reduction in response latency (up to eight views/10cm) but had no effect on accuracy. We conclude for cases where occlusion is not an overriding factor that low viewpoint densities may be sufficient to enable effective path-searching task performance.

Binocular coordination in response to two-dimensional, three-dimensional and stereoscopic visual stimuli

Citation information: Blythe HI, Holliman NS, Jainta S, Tbaily LW & Liversedge SP. Binocular coordination in response to two‐dimensional, three‐dimensional and stereoscopic visual stimuli. Ophthalmic Physiol Opt 2012, 32, 397–411. doi:10.1111/j.1475‐1313.2012.00926.x