At last year’s WWDC, Apple introduced their Metal API for iOS 8. A low-level graphics API, Metal was originally designed to bring the benefits of low-level graphics programming to Apple’s mobile operating system. And while we typically don’t think of mobile devices as being GPU-bound, in reality Apple has been packing some relatively powerful GPUs like GXA6850 with what are relatively speaking still fairly weak CPUs, which means Apple has ended up in a situation where they can be CPU-bottlenecked on draw calls.

Metal, despite being the 3rd such low-level API to be introduced, was the first to reach production status. Microsoft’s DirectX 12 is arguably not there yet (Windows 10 is still in testing), and Khronos’s Vulkan was still in its primordial Mantle form at this point in 2014. What this means is that out of all of the vendors, it’s arguably Apple who has the lead time advantage in low-level API development. Which is why for the last year we have been wondering if Metal would stay on iOS, or make the jump to OS X.

Yesterday we got our answer, with the announcement from Apple that Metal would be coming to OS X “10.11” El Capitan, and that it would be part of a larger investment into Metal for the company. Along with bringing Metal to OS X, Apple is going to be releasing new API kits that interface with Metal to simplify development, and internally Apple is now using Metal (when available) for parts of the desktop composition rendering chain. At this point it’s fair to say that Apple has gone all-in on Metal.

Consequently the fact that Metal is now over on OS X is not unexpected, but whether it has been planned for or not, it means that we now have 3 low-level APIs on the desktop as well as mobile. OS X’s Metal will be going head-to-head with Microsoft’s DirectX 12 and Khronos’s Vulkan, and this is the first time in a very long that we have seen a viable and competitive 3rd graphics API on the desktop, as DirectX and OpenGL have been the reigning APIs since the turn of the millennium.

Metal's Introduction At WWDC 2014 (Image Courtesy Apple Insider)

As for what this means for Mac users, in the short run it’s a good thing. With Vulkan still in development, had Apple not implemented Metal on OS X, OS X would have needed to stick with classic OpenGL for another year until OS X 10.12. Going with their own API, as was the case with mobile, gets a low-level API on OS X sooner. Furthermore because it’s been on iOS for the last year, Apple gets to leverage all of the developer experience and code already written for Metal, and bring that over to OS X. Which is why developers like Epic are able to show off engines using Metal on OS X so early.

In the long run however there are some big unknowns left to answer, which could have a big impact on how things play out. Apple has not yet released the complete documentation for the newest version of Metal – specifically, we don’t have feature lists – so how the Mac and iOS versions compare feature-wise remains to be seen. My biggest concern here is that Apple will put OS X and iOS at parity, essentially limiting the features available to the lowest common denominator of iOS, leading to Macs in general being behind the curve in graphics features. The other big question is whether Apple will support Vulkan next year once it’s done, or whether they will stick with Metal, essentially turning OS X’s graphics stack proprietary. Which for users could lead to a reduction in game ports to the Mac if developers have to go write against a Mac-specific graphics API.

Apple iOS Metal Thread Model

One thing that is a pretty sure bet at this point is the GPUs that will support Metal. In short, don’t expect to see anything that can’t support Vulkan support Metal due to a lack of necessary features. So I’m expecting Metal compatibility to start with Intel’s Haswell (Gen 7.5) iGPUs, AMD’s GCN dGPUs, and NVIDIA’s Fermi/Kepler dGPUs. El Capitan works on a much wider range of machines of course, so this means only a fraction of those machines get to experience Metal. Though this was the same situation on mobile as well.

As for developers, things will be interesting. As I mentioned before Apple seems to be going all-in on Metal, starting with the fact that they will have Metal back-ends for their Core Graphics and Core Animation frameworks. And actually I’m a bit surprised by this, as basic compositing is not something that is draw call limited. Apple is claiming upwards of 50% performance increases here, so I’m curious just how this works out, but I suspect these are based on low-level benchmarks. Draw call performance is not the only benefit of Metal, but it is the most immediate, so Apple may be leveraging the harder to get GPU benefits here, or just wringing every last Joule of power out by getting to an API that isn't doing high-level state checking.

OS X Metal Performance Improvements: From Apple's Promotional Materials

In any case, by building Core frameworks off of Metal, Apple is in a position where they have to ensure Metal drivers are working well, which is to the benefit of developers. Meanwhile Apple is going one step past Metal on iOS 8 with the release of MetalKit, which is a set of utility functions for Metal to help speed Metal development. As we’ve mentioned before one of the few real pitfalls of low-level APIs is that to best utilize them you need guru-level programmers – after all, the API doesn’t have high-level safety nets to keep developers out of trouble – and with MetalKit Apple is at least partially resolving this issue by providing some base functionality for programmers.

Wrapping things up, though not an unexpected move from Apple, it will none the less be interesting to see how their efforts with Metal go. As a tightly integrated vendor they have the advantage of being able to move quickly when they choose to, which is why we’re seeing Metal come to OS X so soon and to get used by Core OS components so soon. Metal is just a graphics API, but due to Apple’s timing OS X will be the real test for low-level APIs on the desktop, and not just for gaming. Apple is in an interesting position to take advantage of these new APIs like no one else can, so in several ways they are going to be the pathfinder on just what can be done with these APIs.

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  • techconc - Wednesday, June 10, 2015 - link

    If you understand how gaming works, this isn't a big issue at all. If you port the top few gaming engines over to Metal, you essentially have the gaming market covered. Apple already did this when the worked with these companies for bringing Metal to iOS 8. They've done this with the Unreal gaming engine, Frost, Unity, etc.
    Additionally, OpenGL is still an option and there is no reason Apple couldn't also support Vulkan, etc. as well. It makes sense for Apple to go all in on Metal because then it controls their own entire graphics stack.
  • TheJian - Wednesday, June 10, 2015 - link

    You must not be aware of the fact that over 1.2 billion devices sold yearly will soon be running Vulkan (and growing yearly it seems). Also by the time it ships they'll all have Tegra X1 level gpus in them at 14nm, even the low end next year will be K1 level gpus and Q1 2017 we start seeing low end at 10nm being X1+ levels of gpu maybe even with some HBM etc helping boost perf. I'd say DX12 is DOA before Vulkan. Nobody will want to code for DX12 if Vulkan is the same feature wise and easier to port from PC to android etc. Unlike previous years, OpenGL didn't have a billion units sold yearly that could push it. Now they do. I see metal the same way as DX12, as programming for either will mean more work to get to the bulk of the world; IE android, linux, steamos etc. I'm sure a port of SteamOS to ARM is on the way, and as all 3 add up to the majority of the world, you'll want to use Vulkan if given a choice and MS/Apple will have to use it too. The only people at that point making Metal/DX12 games will be Apple/Microsoft or people these two PAY to use them...LOL.

    Android just needs another year or so to amp up gpu power across the board and all will be aiming here. Heck they already are, see GDC 2014/2015 survey results. Only PC has more devs aiming at them (51% vs. 49% mobile). I'm not even sure apple will be able to continue to use IMG.L chips once the samsung/qcom suit ends in a settlement shortly. It's doubtful they'll go past the next court date and proceed to trial, as the onus will be on settling rather than face a 12 person american jury wanting to fry samsung for willful infringement for 2+yrs. Apple will take a look and not want their chips/devices banned (runs same img chip as samsung) and will move to rectify their issues. You can't afford to delay a whole launch cycle. Apple will have to deal in some way shape or form (most likely license NV gpu ip or something for future revs+ a pretty hefty settlement to allow shipping the next models already in design etc).
  • techconc - Thursday, June 11, 2015 - link

    I'm not sure what you're talking about. Anyone targeting Windows will want to target DX12 as that will be the most supported environment on that platform. Just as developers will start to target Metal on Apple devices. If anything, Vulkan has the uphill battle to climb. It may be the only choice for Android and even that will be off into the future. If Vulkan ever does take off, there is no reason it can't run side by side with proprietary APIs like DX12 and Metal.
    Also, I don't know what you're talking about regarding Apple moving away from IMG chips. That's not likely to happen and they still offer a competitive advantage over alternatives like Mali, nVidia, etc.
  • Akalack - Thursday, June 11, 2015 - link

    There is much more to Vulkan than just being a low level API, its a modern API and can use GPU's in a way that direct (its still based on archaic GPUs that are very different and much simpler than modern ones) pretty much never will and opens up for more interesting setups and drivers. For example crossfire and SLI is very much a hack that needs to be done differently for every game with a performance loss, however with vulkan its a bit of a different story: it sees every processor and memory as a resource to be used and uses them properly. No memory is wasted, crossfire and SLI is no longer necessary, and it all comes from just using the API. The "only" advantage directx has is developer experience and the xbox.

    Metal is the big unknown now, but doesn't really matter that much outside apple unless they open it for other platforms.
  • tuxRoller - Friday, June 12, 2015 - link

    Mmmhmm...and what happens when android adopts vulkan?
    Let's us not forget that Vulkan will work on windows as well (and driver quality should be far better than is currently the issue with opengl variations).
  • Murloc - Wednesday, June 10, 2015 - link

    El Capitan?
    How do you get there from big cats?

    What next, El Generalissimo? El Presidente? El Capo?
  • jeffkibuule - Wednesday, June 10, 2015 - link

    Mavericks (OS X 10.9) and Yosemite (OS X 10.10) were not cats either. The theme now is places in California.

    El Capitan is a rock formation inside Yosemite National Park in California.
  • nathanddrews - Wednesday, June 10, 2015 - link

    "Look, I'm trying to make an ascent here!"
  • hfm - Wednesday, June 10, 2015 - link

    Through Mavericks and Yosemite.
  • tipoo - Wednesday, June 10, 2015 - link

    Welcome back from your three year coma :P

    They're off cats now, Mavericks and Yosemite were not cats, and this is a place within Yosemite.

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