I have been going through the NEUS paper repository on GitHub and came across a mention of a logistic density distribution in the paper. However, I couldn't find the corresponding implementation in the code.
In the paper, it states:
I am particularly interested in understanding how this logistic density distribution is utilized within the volume rendering process. Unfortunately, I haven't been able to locate the implementation in the codebase.
I would appreciate it if someone could provide guidance on where I can find the implementation of the logistic density distribution in the code.
This is what I managed to get so far:
The equation (13) in the paper 
shows how alpha is calculated. This matches with the 171st line of code in the file models/renderer.py:
alpha = (prev_cdf - next_cdf + 1e-5) / (prev_cdf + 1e-5)
However, I could not clearly track how prev_cdf and next_cdf include the calculation of the logistic density distribution function.
Thanks in advance!