Isaac-Medina, B.K.S. and Willcocks, C.G. and Breckon, T.P. (2023) 'Exact-NeRF: An Exploration of a Precise Volumetric Parameterization for Neural Radiance Fields.', IEEE/CVF Conference on Computer Vision and Pattern Recognition 2023 Vancouver, BC, 18-22 June 2023.
Neural Radiance Fields (NeRF) have attracted significant attention due to their ability to synthesize novel scene views with great accuracy. However, inherent to their underlying formulation, the sampling of points along a ray with zero width may result in ambiguous representations that lead to further rendering artifacts such as aliasing in the final scene. To address this issue, the recent variant mipNeRF proposes an Integrated Positional Encoding (IPE) based on a conical view frustum. Although this is expressed with an integral formulation, mip-NeRF instead approximates this integral as the expected value of a multivariate Gaussian distribution. This approximation is reliable for short frustums but degrades with highly elongated regions, which arises when dealing with distant scene objects under a larger depth of field. In this paper, we explore the use of an exact approach for calculating the IPE by using a pyramid-based integral formulation instead of an approximated conical-based one. We denote this formulation as Exact-NeRF and contribute the first approach to offer a precise analytical solution to the IPE within the NeRF domain. Our exploratory work illustrates that such an exact formulation (Exact-NeRF) matches the accuracy of mip-NeRF and furthermore provides a natural extension to more challenging scenarios without further modification, such as in the case of unbounded scenes. Our contribution aims to both address the hitherto unexplored issues of frustum approximation in earlier NeRF work and additionally provide insight into the potential future consideration of analytical solutions in future NeRF extensions.
|Item Type:||Conference item (Paper)|
|Full text:||Publisher-imposed embargo |
(AM) Accepted Manuscript
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|Publisher Web site:||https://ieeexplore.ieee.org/xpl/conhome/1000147/all-proceedings|
|Publisher statement:||© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.|
|Date accepted:||27 February 2023|
|Date deposited:||19 April 2023|
|Date of first online publication:||No date available|
|Date first made open access:||No date available|
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