It got me thinking that I could do the same in UE4 if I really ‘hammer’ the scene (all foliage shadows on, all whistles and bells to max, hyper-dense foliage etc., expensive models)
It would need quite a few seconds to render, but still very fast compared to static render engines like Vue. Then I would use a 4-5x screenshot (would maybe take a minute), rescale to get good AA and done.
Maybe 10 secs in UE4 would do what VUE needs hours for.
There might be an upper limit, but it’s probably higher than 10 seconds. Taking a high res screenshot is not dependent on that. The only concern with that is that you need enough memory to do it depending on how big the image will be.
one thing you will run into is Timeout Detection & Recovery (TDR), when the render time goes past a point your driver will timeout and restart, even though its still rendering the frame. this will crash UE4. you can tweak the timeout value in window registry:
TdrLevel can be used to turn off TDR
TdrDelay can be used to set a new timer
beware though having a long timer or none at all can and will cause BSOD if your driver has a problem it wont recover.
I might actually not need very long. I checked out Speedtree a few days ago and the trunks are basically as good as it gets. The leaves by default look a bit cheap, but just using huge numbers and actually using single leaves should do it.
To rival a VUE render, I think it just needs huge foliage amounts and high poly models. A high end GPU should not need more than 1-5sec, even with the UE4 overdraw issue that makes foliage renders slower than in Cry Engine.
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I put one of my in-game screenshots next to the VUE renders. Already not to far off I think. http://www.cornucopia3d.com/galleries/displayimage.php?album=lastupby&cat=0&pos=0&pid=70767