Interlaced mode

Are the optimisations for running interlaced just built in? I’ve got a project which has been always destined for a 1080i output, but I was always developing on a 1080p screen mode (at 60fps - which is essential). I was very pleased to see the performance skyrocket when I plugged in a normal TV at 1080i. Does the renderer know it’s running in this mode - effectively 1920x540 and do all the required stuff to make this look correct? Is there a way to explicitly force the engine into this mode even though I’m on a 1080p monitor (it’s actually a 4k monitor)?

I know a lot of consoles run in this mode so I’m sure it’s all in place - but what about the console commands?

Thanks for any help there!

UE4 does not render in interlaced mode, your video card controls what’s output to your TV.

I’m not aware of a way to control x and y independently, but the console commands sg.ResolutionQuality 0-100 and r.ScreenPercentage 0-100 can simulate lower resolutions. You’ll see a corresponding increase in performance. When testing in the editor, adjusting Settings->Engine Scalability Settings -> Resolution Scale can accomplish the same thing.

I’m actually overcranking the resolution to 200 percent, which makes everything look a lot nicer - this is the desired effect, but when i’m running 1080p the machine just can’t keep up and runs at about 30fps. If I run on a 1080i screen I can max it out at 60fps. There must be a reduced vertical render dimension, and the engine is adjusting the aspect ratio to suit it.

Historically, when rendering to an interlaced format (20 years as an editor with graphics credentials) the renderer, be it 3ds or whatever uses a comb like filter as it renders odd then even lines - This means that when the image is still you get a crisp look as if it’s a progressive image, but when it’s moving you get twice the effective frame rate because of the 50/60hz interlacing.

My software is for use on TV so it really has to lock to 50/60 fps.

  • In reply, Darthviper, I think the engine must render 2 half height images which are sent for combining in the graphics card’s frame buffer.