Document the parameters of the procedural/scene format

**Describe the feature you'd like**
We should document the parameters of the procedural and the scene format.

**Describe the solution you'd like**
Possibly as part of doxygen, using a markdown file.

No source file, test, or documentation entry point is named. First locate where the procedural and scene format parameters are defined and how Doxygen or Markdown documentation is organized; done means the parameters for both formats are documented in the chosen location.

Written by the indexing model from the issue text.