I'm trying to move my game development into the third dimension, but I'm having a bit of troubles understanding what I actually have to do. I've created a 2D MMORPG before using C and SDL, which wasn't too hard. But I can't seem to find any useful resources explaining how 3D programming actually works. I have a basic understanding of the vector math involved, but I just can't seem to find any clear, in-depth explanation of how everything else like lighting and shaders work. I've found plenty of code samples and such, but all of them just throw in a comment like "//Apply the lighting", which doesn't really tell me anything about what it's actually doing and why.
I'm not looking for an API-Specific tutorial; it's easy enough to learn a new API--I'm just not sure what to actually do with it.
If you are looking for a book, I highly recommend Real-Time Rendering. I have the second edition of the book and found it be a great asset when working with 3D graphics. The book explains the innerworkings of the building blocks of 3D programming, like transforms, lighting and textures. It also explores a variety of advanced topics, including shaders, collision detection, acceleration and optimization.
The book is very light on code. It explains algorithms in depth but does not contain real code snippets. So it is very good if you want to learn how things work instead of just knowing which function to call.