Texture Mapping Tip (Reflection maps, Matcaps, Lightmaps, etc)

[KamauKianjahe]

I'm not sure if this has been discussed here before but for the sake of being thorough, I wanted to talk about these textures some old games use to fake highlights, shadows, and reflections. I knew them as ref maps, but they're more widely referred to as matcaps I think. Blender -2.79 had this mapping type in Blender Internal or "Blender Render" by default called Normal mapping, but that often refers to other things these days.

I bring this up because of these shadow android models an old friend of mine TheSonofChaos ripped. These characters are primarily textured by this metal texture that's intended to be mapped with reflection/matcap mapping: 
   

Here's the model with the texture applied with ordinary UV mapping. This is also how you'd see the texture upon import:
   

Here's the model with the intended mapping. Every texture from the lights on the gun, gold rings, and body texture use this mapping method: 
   

Other characters in this render engine also use black and white reflection textures to add/overlay some lighting- this of course is the infamous Sonic Heroes shininess for example. Here's the method for mimicking this mapping style in blender eevee/cycles:
Quick and Easy Method:     
Complex/Accurate Method: Matcaps in EEVEE (New method) - BlenderNation

This has alluded me for a ridiculously long time, so I spread the word whenever possible. If this is common knowledge, I'll gladly take my ball and go home.

Thanks for readin'