About Deffered rendering with Metal

I find that this feature is still WIP and not available in 4.9p4,I’m wondering when it will be available without spending time compiling the editor…Will it be available in 4.9 release or 4.10?And could you tell me what’s the difference between deferred and forward rendering?Thanks a lot!

We paused on it while we started working on Metal on the Mac (which is always deferred, so iOS will just reap the rewards).

We are merging much of the code from a Metal development branch into the main branch of UE4, but it’s not clear if it’s going to be working for 4.10 or not. Certainly we are focusing on Mac right now, but trying to keep iOS MRT stuff as functional as it was.

Deferred rendering is a method that allows for our high end rendering features (basically, it’s the desktop renderer). However, it’s not actually well suited to the Tiled GPUs that are in all iOS devices, and many mobile devices in general. There is one main weakness of Tiled GPUs, which is many rendering passes where the render targets need to go out to memory. Deferred rendering has dozens of passes, forward rendering only has a few.

So, while we are working on the feature set for iOS, it’s not going to be optimized very well for awhile, or until the hardware is fast enough to make it work well enough.

Hope this helps!
Josh

Thank you very much for explaining that for me.So you mean that on Macos,I can directly build MRT for ios without building the source code?

When I said Metal on Mac, I meant the new ability of MacOS to render with Metal, not building for iOS on the Mac. As we demoed at WWDC, we are adding support to the MacOS version of Metal, but it turned out to be a huge job, and merging it back to main hasn’t been trivial.

Many of the changes needed for Metal on Mac are what’s needed to finish MetalMRT on iOS (Metal on Mac and MetalMRT on iOS are both using the deferred path, so most of the work is the same).

That said, you can try running the game with -metalmrt (if you check the checkbox in the project settings to support it), and I think it will work. However, it’s a work in progress, so don’t expect great things until we get the Mac stuff merged back in to main, which will be 4.10 or 4.11, depending.

Josh