I have split the project into 2 separate Git repositories.
This is the new repository that contains the STL viewer and the STL thumbnail.
The newer STL thumbnail extension to WFE has alot of improvements. The most obvious is that it is alot faster.
There is still an issue.. There is some “whitewalkers”. This is because the STL contains info abot that the color of the STL should be white. This overrides the choice of color.
I have also tried some real big STL files. Sometimes the background becomes black and not transparent. Irritating, but not a big deal.