Very good extended documentation. The README.md in the project folder should serve as main documentation, and point to all specific documentation pages (installation, exampes, code documentation, etc ...).
Some warning because coming from dependency code, but I won't remove points for that.
Use of YAML files, with complete parameter settings.
You developped quite a lot of features, a GUI, a lot of parameters. And even if there is some examples to get inspired from, it's quite hard to see how to do simple things, or to build a scene from scratch, or to understand the significance of each parameter in a scene setting (for instance, what is the far/fov parameters for the camera ?). So at the end, it's quite an impressive huge machinery, but I'm not sure that people (other than you) would easily use your program.
All right.
A bit messy (PlantUML would have been more clear than Mermaid for that), and hard to distringuish between inheritance, composition and aggregation. Also, there is no interface in C++ : it's a Java concept, which roughly corresponds to a fully abstract class in C++ (only abstract methods, i.e prototype for class inheriting from it).
None seen
Automatically build using CMake (good!), however still missing some main code documentation file.
Lot of additional libraries used.
2 - Implementation of required features (primitive objects, transformations, combinations and light model) : 1.5/2 points
Missing combinations (intersection, union, ...)
None seen
Plenty on that side (GUI, textures, vox reading, ...)
Final grade : 14 / 20 => 3.5 bonus points
General remarks : A lot of additional features, which is great. However, the more complex your program is, the more detailled the use documentation (and code) should be. Don't forget that the best softwares are not necessarily the one that can do gazillion of impressive stuff, but more the one that other people can easily use. So don't go too fast in code development, and update the (user/code) documentation that comes with it.