DirectX 12 runs on XBox One, while Vulkan does not:
> http://www.redgamingtech.com/directx-12-for-xbox-one-is-here...
And for OSX/iOS, you have to use OpenGL or Metal.
And the Switch uses Vulkan; while Vulkan on top of Windows (including 7 and 8/8.1) supports Linux and Android. For iOS and macOS there's MoltenVK, but I can't speak for its quality.
https://blogs.nvidia.com/blog/2016/10/20/nintendo-switch/
So it remains to be seen which one gets the love of game developers.
That's actually a fairly interesting question, given the percentage of games that come out for Nintendo platforms which are exclusive to that platform (or at least to the Nintendo family of platforms). There are all the first party titles, and then there are all the esoteric games which don't really fit the control schemes of the other platforms (but the switch is less unique in this aspect). I imagine games targeted purely at Nintendo platforms might use their proprietary API, especially first party games, which might get the API changed based on their needs.
It doesn't run on Sony PS4, Nintendo Wii U, XBox ONE, UWP, OS X, iOS, tvOS.
Even on Android it is going to take a while until most people exchange their handsets for ones having it, because the majority will never get an upgrade for Android 7.
Only OpenGL ES 3.2 is mandatory.
This was probably made for chipset producers; if Vulkan was made mandatory, you would see exactly 0 updated devices.
Source: Android 7.1 Compatibility Definition Document
Chapter 7.1.4:
Device implementations MUST support both OpenGL ES 1.0 and 2.0, as embodied and detailed in the Android SDK documentations. Device implementations SHOULD support OpenGL ES 3.0, 3.1, or 3.2 on devices capable of supporting it.
Chapter 3.3.1:
Note that device implementations MUST include libGLESv3.so and in turn, MUST export all the OpenGL ES 3.1 and Android Extension Pack function symbols as defined in the NDK release android-24. Although all the symbols must be present, only the corresponding functions for OpenGL ES versions and extensions actually supported by the device must be fully implemented.
Chapter 3.3.1.1:
Device implementations, if not including support of the Vulkan APIs:
- MUST report 0 VkPhysicalDevices through the vkEnumeratePhysicalDevices call.
- MUST NOT delare any of the Vulkan feature flags PackageManager#FEATURE_VULKAN_HARDWARE_LEVEL and PackageManager#FEATURE_VULKAN_HARDWARE_VERSION .
Chapter 7.9.2:
Android handheld device implementations MUST identify the support of high performance virtual reality for longer user periods through the android.hardware.vr.high_performance feature flag and meet the following requirements.
...
- Device implementations MUST support OpenGL ES 3.2.
- Device implementations MUST support Vulkan Hardware Level 0 and SHOULD support Vulkan Hardware Level 1.
....
If the engine needs two rendering interfaces, the effort is exactly the same as OpenGL ES + whatever else.
Unless you are suggesting game developers should be happy to sell only to LG V20, Samsung S7 and Google Pixel owners.
Turnaround in the mobile hardware space is even faster than on the desktop (let alone stagnating consoles), so Vulkan availability is much less of an issue there.
It doesn't matter if the drivers are available if those GPUs aren't on the motherboard.
Currently Vulkan is constrained to 2.8% of the Android market.
> Turnaround in the mobile hardware space is even faster than on the desktop (let alone stagnating consoles), so Vulkan availability is much less of an issue there.
Only in US, not everyone around the world, specially in countries where pre-pay is the way to go, changes their mobile every two years.
My point is, this situation will be shorter than on the desktop. Because as I said, the turnaround of mobile hardware is faster.
> ly in US, not everyone around the world, specially in countries where pre-pay is the way to go, changes their mobile every two years.
In US too, not everyone is going to buy every new model. I'm talking however about manufacturers making them. That happens pretty fast. So Vulkan support on new hardware is probably already a given and this whole thing is a non issue. Any new technology has adoption period.
DX12 is not DX11+1. It's a clone of AMD's Mantle, which was eventually given to Khronos, so they make it into Vulkan. The main advantage of Vulkan is that it runs almost everywhere. DirectX 12 doesn't.