[Gear VR] UE 4.12 with HDR on running slow on Gear VR, but blazing fast on Daydream - why?!

Thanks for reporting this. We'll take a look. Are you using the same eye buffer resolution for both cases?

I am not really sure. Here is the OP and I will ask the person who tested to reply to your question:

https://forums.unrealengine.com/showthread.php?113200-Has-anyone-tested-4-12-with-Gear-VR

Hey vrdaveb,

"Are you using the same eye buffer resolution for both cases? "

I'm not sure about that how can I check? - I just did a pure gearvr export and compared to a pure daydream export of exactly the same project without changing any settings and both running on the same device S7 edge exynos chipset with UE4.12

The performance difference is very large for my project at least. ~30FPS on the gearvr versus 60FPS on cardboard/daydream.

Let me know if you require any further details

What is the value of r.ScreenPercentage for each case?

I definitely do not change that value at all but now wondering if UE4 changes it automatically under the hood so tested it out - not so easy to 'get' this value btw over wifi but here we go:

daydream export: 100
gearvr export: 100

but I did notice this in the logs just before any image is shown:

daydream export: "LogRenderer: Reallocating scene render targets to support 1280 x 720"
gearvr export: "LogRenderer: Reallocating scene render targets to support 2560x1440"

So I guess gearvr is just running in a higher resolution? Any idea how to change the resolution of my gearvr export down to 1280x720 to test this? As to be honest at first glance I didn't notice much difference from the resolution looking directly at the image on the display

@vrdaveb @aussieburgerVR  I am wondering what's the verdict here :/

Yeah UE4 is obviously exporting with different settings for both plugins that causes the performance differences.

From https://forums.unrealengine.com/showthread.php?113468-GoogleVR-No-antialiasing-at-all&p=545612#post545612

you can see googlevr has no AA whereas GearVR has MSAAx2 which would account for performance drop as well as being half the resolution.

I'd like to know if there was a way to lower the resolution of gearvr exports a bit to get a trade off for better performance for more details ...

Ooh, cheeky Google... 

I tried scaling resolution and it doesn't seem to work outside of PIE (at least not on the device).