Graphic pipline and Image post processing

Hi! I’m new to UE and specially to it’s source code^_^

I done only a general CG course and played a lot with Unity, I’m curently very intrested in writing Shaders and interfer during the graphic pipline.
I downloaded and build UE project in VS and I was wondering if there is a way to change the light equation,
simulary like in OSG that based on OpenGL when I could, for example:
instead of adding all the element diffuse, ambient, specular, emissive variables, multiple all of them (I=D+A+S+E -> I=DAS*E).

Also I would be glad for any refernce or examples about writing shaders and genral post image processing (CUDA, OpenCL…)
I found couple refernces that was very informing:

But I was wondering if there is any new examples or tutorials on this subject.

Hope you’ll be able to help me to get some directions and that I’m not too lost noob.