I've been playing some Dishonored 2. I'm pretty far into it and I've made it to a level where you use a gadget called a "timepiece" to look into (and travel to) the past. Remember when Titanfall 2 did that? Well, this game does the same thing, and came out at pretty much the same time. Weird coincidence. Anyway, what Titanfall 2 didn't have was a way for you to look at what's happening in one time period while you're actually standing in the other. Like so:

But I noticed something funny while running around with this thing open. My framerate is all over the place. It's at a healthy 58 in that picture, but most of the time this game is hanging around the 80-100 mark for me and opening this timepiece up pretty much halves that every time and makes my poor old 970 scream in protest.

So I'm really wondering two things - the first is, are they really rendering two different things at once, one in the past and one in the present? And would there be a more efficient way of doing this?

Bonus question: How well does this bit do on consoles? Jindosh's mansion also wasn't too kind on my graphics card, so I kinda started wondering how well the PS4 and Xbox One ran this game. EDIT: Come to think of it, Jindosh's mansion might have had poor performance in places more because of my aging CPU, which is an i5 3470.

I don't know about Dishonored 2; but, Titanfall 2 rendered two levels, one on top of the other, so I think it's safe to assume it's a similar thing here.

I loved this level. I suspect it must be rendering both but I'm no wizard. This whole trick is my favourite gimmick in games lately. I love the Looking Glass stuff in Prey for similar reasons. Its a part of videogame tech that still feels like magic to me.

Yeah that level in Dishonored 2 blew my mind. I had never seen anything like that done before and it was so smooth. I was also wondering how it was done but I didn't notice performance issues on my 1080 and just chalked it up to magic.

Yeah it's rendering everything twice similar to Portal, Antichamber and the both Prey games. I'd guess that the crystal things the other environment appears in use a render texture and it looks like the normals of the crystals are creating a wobble to the image where cracks and fractures are. Also why you probably get the performance hit because the second render is always fully in view so it can't be disabled when not visible or have it's resolution and frame rate reduced.

Here's a link to a video that describes in very simple terms how it works. You can also read the comment chain in that video started by Fabrice Piquet for a few more details on how it works.

https://youtu.be/yKxMlIqMUAY?t=2m31s (the time stamp is where they explain it)

"rendering twice" is a misnomer. they only render what they need to out of the two scenes. it's very similar to the way portal works (rendering to a texture) but the camera is in the same place in another scene

I figured saying it that way wasn't exactly correct, but I was looking for a way to condense the idea into a small word or phrase.

This is what I was looking for, thanks!

I can see why someone might love this level, but I wound up not liking it much at all. They took away all of my powers and the powers are what have been making Dishonored 2 so much fun for me, especially Blink. That, and the Timepiece takes up a huge portion of your screen when opened up and it makes some annoying background noises (much like the Heart does). It's exceptionally well-designed, but I sorely missed those powers for an entire level.

I played through the entirety of the game on the Xbox One and do not remember any frame rate issues. At least not anything too terrible that would stick with me.

Played through it twice on my launch PS4 and didn’t have any frame rate issue either. They did a really good job getting this and the clockwork mansion to run smoothly on consoles.

You guys keep going on about "both" versions of the level. But remember that there is actually a third variation of the level that overwrites the ruined one if you travel back and knock out Stilton so that he never attends the seance thing and goes crazy.

Like people are saying, both levels are probably loaded at the same time when you start the level, but only stuff nearby is being rendered.

If I had to guess I'd say problems with framerate might be occuring because of enemy AI, as guards continue pathing and following their cycles even when not being rendered on screen.

I played it twice or more on my launch PS4 and the framerate was noticeably worse than the rest of the game, but Dishonored 2 overall didn't run all that amazing on PS4. Then again I also had framerate issues with AC Origins that apparently everyone else was fine with so who knows, maybe I need to blow some air into my console to get the dust out or something.