Whops, seems you're right... this tells how to compute the projection matrix:
https://gamedev.stackexchange.com/quest ... -in-opengl
But you don't need to do it by hand, because Java3D has a ready made mathod for this:
https://download.java.net/media/java3d/ ... %20double)
Java3D is embedded in SH3D installation, so you just need to add it to your build path, you don't need to embed it in your plugin.