OpenGL ES 2.0的学习曲线是否比Metal更陡峭？

Question

I'm very interested in 3D graphics and heard many developers raving about Metal.

Can someone who has worked with Metal and OpenGL ES 2.0 comment on how the learning curve compares to OpenGL ES 2.0?

As a beginner who aims to stay loyal to iOS, is Metal easier to learn and master than OpenGL ES 2.0 or is it harder because it is more advanced?

I hope this question will be useful to many as I am trying to figure out where to start.

Answer 1

As a beginner, you might be better served by starting with 3D graphics at a higher level. SceneKit for OS X and iOS lets you describe a 3D scene in terms of its content -- geometry, materials (textures/shading), lights, and cameras -- and load assets created with 3D modeling tools. SceneKit is built on OpenGL (ES), so it uses a lot of the same concepts. As you become familiar with those concepts, you can use SceneKit to work your way into the OpenGL world a bit at a time:

• use shader modifiers to write GPU shader code that extends SceneKit's
• use custom programs to write complete shaders that replace SceneKit's, or techniques to write shaders that postprocess SceneKit's rendering
• create custom geometry from your own vertex data with geometry sources & elements
• use a node renderer delegate to write your own OpenGL client code that works within a scene

You'll find more info about all of these by watching the SceneKit videos from WWDC: What's New in SceneKit and Building a Game with SceneKit .

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Otherwise... OpenGL (ES) and Metal don't have very different learning curves in and of themselves. In fact, I'd consider Metal more approachable than OpenGL in some ways -- for example, many things you can do in GL have implicit and hard-to-predict performance costs, and the Metal analogues of those tasks are much more clear about their impact on CPU or GPU time is and allow you to decide when expensive work gets done.

On the other hand, Metal is brand new -- there aren't yet a lot of third-party resources to help you learn it. And lot of the hard things about learning 3D graphics are very similar whether you're working in Metal, OpenGL, DirectX, or another platform/API. Once you learn the important stuff -- there are plenty of books and online tutorials for that, but StackOverflow isn't the best way to go looking for them -- getting up to speed with Metal or with OpenGL ES on a specific platform is pretty easy.

Answer 2

Coming from an OpenGL-ES background, I had a good look at the Metal APIs. I believe that the learning curve for Metal is steeper, not because it's a new API, but because it introduces low level constructs which developers previously didn't need to worry about.

If you compare fixed pipeline Open-GL with shader oriented Open GL flavours (On mobile: ES 1.x compared with ES 2.x, 3.x), and finally with Metal, what you have is increasingly powerful, increasingly generic APIs detached from the intuitive constructs (triangles, vertices, lamps) which constitute Open-GL's historical foundation.

Bear in mind that creating a more usable API isn't the main goal of Metal. The goal of this framework is helping developers to get rid of driver overheads.