Möbius boosts enable shear-free 360° viewport zoom with +3.26 dB PSNR gain

Viewport-adaptive 360-degree imaging aims to allocate limited sampling budget to regions a viewer is likely to observe. Existing view-biased projections increase resolution through non-conformal warps, which introduce anisotropic stretching and shear, degrading visual quality. Researchers Boyang Li and Hezhao Xu from an undisclosed institution propose Spherical Möbius Boosts as exact conformal maps for fixed-budget viewport magnification. The continuous spherical warp maintains quasiconformal dilatation K=1, meaning local angles are perfectly preserved while samples are concentrated toward a target direction. This eliminates the shear distortion common in offset cubemaps and other projection methods.

On a SUN360 saliency audit comprising 72 panoramas and 216 paired viewport targets, C1 Möbius boosting outperformed optimized offset cubemaps on every paired case. The case-level median PSNR gain was +3.26 dB, with image-level median +3.23 dB and a panorama-level bootstrap 95% CI of [+3.15, +3.33] dB. However, Pareto analysis reveals a trade-off: the method sacrifices full-sphere WS-PSNR for shear-free viewport fidelity. Prediction-error and filtering studies show that strong boosts work best for accurately targeted viewports, while large target uncertainty calls for weaker boosts or fallback. The result positions Möbius boosting as a geometric primitive for prediction-conditioned foveated 360-degree resampling rather than a universal encode-once layout.