Globally and Locally Optimized Pannini Projection for High FoV Rendering of 360-degree Images

TL;DR

This paper introduces a content-aware Pannini projection method that globally and locally optimizes high field-of-view rendering of 360-degree images, reducing distortions and improving visual quality.

Contribution

It presents a novel automatic projection technique combining global content-based optimization with local refinement for high FoV 360-degree images.

Findings

Crowdsourcing tests show high user preference for the proposed projection.

The method effectively reduces geometric distortions in high FoV renderings.

The approach outperforms existing sphere-to-plane projection methods.

Abstract

To render a spherical (360 degree or omnidirectional) image on planar displays, a 2D image -- called as viewport -- must be obtained by projecting a sphere region on a plane, according to the users viewing direction and a predefined field of view (FoV). However, any sphere to plan projection introduces geometric distortions, such as object stretching and/or bending of straight lines, which intensity increases with the considered FoV. In this paper, a fully automatic content-aware projection is proposed, aiming to reduce the geometric distortions when high FoVs are used. This new projection is based on the Pannini projection, whose parameters are firstly globally optimized according to the image content, followed by a local conformality improvement of relevant viewport objects. A crowdsourcing subjective test showed that the proposed projection is the most preferred solution among the considered state-of-the-art sphere to plan projections, producing viewports with a more pleasant visual quality.