Computer Graphics Laboratory ETH Zurich

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Multi-planar plenoptic displays

N. Ranieri, S. Heinzle, P. Barnum, W. Matusik, M. Gross

Journal of the Society for Information Display, Blackwell Publishing Ltd, vol. 21, no. 10, 2013, pp. 451-459

Abstract

Multi-planar plenoptic displays consist of multiple spatially varying light-emitting and light-modulating planes. In this work, we introduce a framework to display light field data on this new type of display device. First, we present a mathematical notation that describes each of the layers in terms of the corresponding light transport operators. Next, we explain an algorithm that renders a light field with depth into a given multi-planar plenoptic display and analyze the approximation error. We show two different physical prototypes that we have designed and built: The first design uses a dynamic parallax barrier and a number of bi-state (translucent/opaque) screens. The second design uses a beam splitter to co-locate two pairs of parallax barriers and static image projection screens. We evaluate both designs on a number of different 3D scenes. Finally, we present simulated and real results for different display configurations.

Figure 1: Illustration of the decomposition algorithm for a display layer configuration of one front-most modulating layer followed by three emissive layers. View independent emissive elements are assigned, occlusions computed and the residue added using parallax barrier rendering.

Overview

Glasses-free 3D displays have experienced a major renaissance in the past few years. In general, these displays can be divided into two main categories: parallax-based displays and volumetric displays. Parallax-based approaches such as integral imaging and parallax barriers redirect spatially varying pixels onto different viewing directions. These approaches trade off spatial resolution in favor of angular resolution, which directly relates to the depth range that can be displayed without aliasing. Though being capable of view dependent effects and proper occlusions, these devices often exhibit low spatial or angular resolution and lack correct accommodation cues. Volumetric displays, on the other hand, physically deploy light-emitting voxels in 3D space and provide a direct and natural approximation of the input scene. They provide correct accommodation cues but are, with few exceptions, not capable of providing proper occlusions or view dependent effects.
As alternative, multi-planar displays have been suggested to provide natural ways to show 3D scenes at nearly correct accommodation cues with increased display bandwidth and hence higher angular and spatial resolution. In essence, these displays combine parallax and volumetric displays and draw benefits from both. In our work, we generalize these concepts to multi-planar plenoptic displays by defining basic display layer primitives, consisting of emissive and modulating layers.

Figure 2: Two views captured on our spatially multiplexed prototype with clearly visible parallax and proper occlusions. The spaceship is rendered on the front layer where to moon is displayed by the layer in the back.

Results

We demonstrate several examples for both the spatially and temporally multiplexed setups. Figure 1 shows all steps of our algorithm. Figure 2 shows real results displayed on the spatially multiplexed prototype with visible parallax between the two views. Our displays are quite unique since an observer is provided with accommodation cues, visible in Figure 3, as well as binocular cues and motion parallax. In addition to this, view-dependent effects can be observed clearly and they add to the depth perception. We believe that the superimposed spatial modulator does not significantly influence the accommodation cues.

Figure 3: Multi-planar plenoptic displays provide good accommodation cues as visible in these images, captured on our spatially multiplexed prototype with different camera focus.

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