Neural radiance fields (NeRFs) are able to synthesize realistic novel views
from multi-view images captured from distinct positions and perspectives. In
NeRF's rendering pipeline, neural networks are used to represent a scene
independently or transform queried learnable feature vector of a point to the
expected color or density. With the aid of geometry guides either in occupancy
grids or proposal networks, the number of neural network evaluations can be
reduced from hundreds to dozens in the standard volume rendering framework.
Instead of rendering yielded color after neural network evaluation, we propose
to render the queried feature vectors of a ray first and then transform the
rendered feature vector to the final pixel color by a neural network. This
fundamental change to the standard volume rendering framework requires only one
single neural network evaluation to render a pixel, which substantially lowers
the high computational complexity of the rendering framework attributed to a
large number of neural network evaluations. Consequently, we can use a
comparably larger neural network to achieve a better rendering quality while
maintaining the same training and rendering time costs. Our model achieves the
state-of-the-art rendering quality on both synthetic and real-world datasets
while requiring a training time of several minutes.

本研究提出了将本应在神经网络评估后再进行渲染的颜色，改为直接渲染出射线查询的特征向量，从而大幅降低了神经网络评估的复杂度和计算开销，并取得了较好的渲染质量。