3D Graph of Energy Distribution

I wanted to post a 3D graph since we've been studying 3D displays this week in lecture. Many of the graphs I came across were unnecessarily 3D, rendered in 3D to produce a more fascinating aesthetic, and created by someone uninterested or unaware of Tufte's data-ink principle. However, this graph's 3D nature seems to serve a purpose, with three different axis measuring different aspects of energy distribution. Unfortunately, each axis is not labeled, and because of this, I can't comprehend what the graph represents. Also, it is unclear whether or not the coloring of the graph represents a fourth dimension or if it is unnecessary ink. If it does represent a fourth dimension, then a key is needed.