I’ve been doing about an hour of research on this, coming from zero graphics experience. The official website says that OpenGL ES 2.x is defined relative to OpenGL 2.0. However, I’ve read that a major difference between 2.0/3.0 is the deprecation of the fixed-function pipeline (no idea what that is at this point), and that ES 2.x doesn’t have a fixed-function pipeline. These last details are what’s confusing me.
The reason I’m asking is because I’m considering buying the OpenGL Superbible 5th Edition. According to the author and some Amazon reviewers, this book is heavily biased towards OpenGL 3.0, and it’s actually recommended to get earlier editions for OpenGL 2.0. Considering that I’m mainly interested in ES, which OpenGL version is most relevant, 2.0 or 3.0?
Also, if for some reason I decide to go with ES 1.1, I’m assuming a 2.0 book is the right choice?
OpenGL 2.0 was the first with a programmable pipeline, but it operates in tandem with the fixed pipeline, so for example you can write a vertex shader (roughly, a thing that defines how a position in 3d space is transformed into a position on the screen) that just says ‘use the fixed functionality code’. You’re no longer meant to do that under 3.0 as the fixed stuff is deprecated – you’re explicitly warned that it may vanish in the future.
Unfortunately, the GL shading language used with GL 3.0 is ahead of that paired with GLES 2.0 (1.30 for the former, a slimmed 1.20 for the latter). And it’s not just esoteric features that differ, it’s some fundamental naming things that aren’t going to be so nice when you’re starting out. E.g. GLSL ES 1.0 (as in GL ES 2.0) sticks to the concepts of uniforms (things you specify at most once per triangle) and varyings (things you calculate per vertex and the hardware works out intermediate per-pixel values for automatically). GLSL 1.30 looks towards potential future additional programmable pipeline stages so prefers a more abstract idea of inputs and outputs to each part, producing different keywords and hence a different syntax. It’s not hard to map the one to the other, but possibly a real hurdle when starting.
Ideally, start with a genuine GLSL 2.0 text. Because 1.x is all about fixed functionality, there’s no point working up if you’ve genuinely no interest in learning the older API – pretty much everything beyond how you hand data to the GPU is different.
However, if you do want to learn ES 1.x from a desktop text then books on 1.5 are the way forward. 1.5 is the API upon which ES 1.0 is based, with most of the inefficient or rarely used bits of functionality cut off.
Conversely, webGL is exactly ES 2.0 in the browser, and being directly of interest to web developers is likely to become well documented on the web. It might be an idea to look into that.