Digging through my old archive, I found this old documentation for a matcap shader I wrote for Halo 4 a few years back. Our pipeline was entirely proprietary, and didn't feature any kind of node based editor such as Unity's ShaderForge or UDK's shader editor.
Luckily my previous experience working on the hardware side at Nintendo Technology Development and interfacing with OpenGL at a low level helped me find my way around our engine.
Much of my work nowadays doesn't require the level of linear algebra as it used to, but I still find concepts derived from that foundation useful for debugging collision and raycasting logic in my character/camera controllers. Like anatomy knowledge, linear algebra has a very low decay, and I'm very glad to have invested in adding that to the tool belt.