Analyzing the Internals of Neural Radiance Fields

Fuente: arXiv
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Hauptverfasser: Radl, Lukas, Kurz, Andreas, Steiner, Michael, Steinberger, Markus
Format: Preprint
Veröffentlicht: 2023
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author Radl, Lukas
Kurz, Andreas
Steiner, Michael
Steinberger, Markus
author_facet Radl, Lukas
Kurz, Andreas
Steiner, Michael
Steinberger, Markus
contents Modern Neural Radiance Fields (NeRFs) learn a mapping from position to volumetric density leveraging proposal network samplers. In contrast to the coarse-to-fine sampling approach with two NeRFs, this offers significant potential for acceleration using lower network capacity. Given that NeRFs utilize most of their network capacity to estimate radiance, they could store valuable density information in their parameters or their deep features. To investigate this proposition, we take one step back and analyze large, trained ReLU-MLPs used in coarse-to-fine sampling. Building on our novel activation visualization method, we find that trained NeRFs, Mip-NeRFs and proposal network samplers map samples with high density to local minima along a ray in activation feature space. We show how these large MLPs can be accelerated by transforming intermediate activations to a weight estimate, without any modifications to the training protocol or the network architecture. With our approach, we can reduce the computational requirements of trained NeRFs by up to 50% with only a slight hit in rendering quality. Extensive experimental evaluation on a variety of datasets and architectures demonstrates the effectiveness of our approach. Consequently, our methodology provides valuable insight into the inner workings of NeRFs.
format Preprint
id arxiv_https___arxiv_org_abs_2306_00696
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Analyzing the Internals of Neural Radiance Fields
Radl, Lukas
Kurz, Andreas
Steiner, Michael
Steinberger, Markus
Computer Vision and Pattern Recognition
Graphics
Modern Neural Radiance Fields (NeRFs) learn a mapping from position to volumetric density leveraging proposal network samplers. In contrast to the coarse-to-fine sampling approach with two NeRFs, this offers significant potential for acceleration using lower network capacity. Given that NeRFs utilize most of their network capacity to estimate radiance, they could store valuable density information in their parameters or their deep features. To investigate this proposition, we take one step back and analyze large, trained ReLU-MLPs used in coarse-to-fine sampling. Building on our novel activation visualization method, we find that trained NeRFs, Mip-NeRFs and proposal network samplers map samples with high density to local minima along a ray in activation feature space. We show how these large MLPs can be accelerated by transforming intermediate activations to a weight estimate, without any modifications to the training protocol or the network architecture. With our approach, we can reduce the computational requirements of trained NeRFs by up to 50% with only a slight hit in rendering quality. Extensive experimental evaluation on a variety of datasets and architectures demonstrates the effectiveness of our approach. Consequently, our methodology provides valuable insight into the inner workings of NeRFs.
title Analyzing the Internals of Neural Radiance Fields
topic Computer Vision and Pattern Recognition
Graphics
url https://arxiv.org/abs/2306.00696