Custom 32x32x32 LUTs without shaders

[torridgristle]

It occurred to me that internally the NTSC gamma adjustment is done with a 32-entry LUT, and a 32x32x32 3DLUT for CRT-like color correction could be similarly implemented with (I assume) less resource usage than a GLSL shader doing texture lookups and unnecessary blending.

Here's a blank 32px 3DLUT for example. https://i.imgur.com/Ev6K4XQ.png

Here's my loose approximation of a JVC TM-1650SU CRT. https://i.imgur.com/uZQYIM2.png

Here's a comparison of a Super Game Boy screenshot with and without the JVC 3DLUT to show you why I'm interested in it. https://i.imgur.com/oVE75Mx.gif