The Tech & Beauty behind Epic’s UE4 Open World Demo

GDC 2015 in San Francisco was full of impressive Game Technology Demos and especially the Team of Epic Games came packed with a bunch of material to reveal.

Since I couldn’t attend in person, I had to stick to livestreams and tweets – but fortunately there wasn’t lack of information sharing – a lot of live twitch streams enabled me to get most of the interesting sessions streamed across the Atlantic right to my computer (unfortunately except the VR Session by Epic with WETA, which for some reasons wasn’t allowed to be streamed).

One thing that really stood out to me was Epic’s Kite Open World Cinematic – and the fact it was rendered completely in realtime (1080p @ 30fps on Nvidia’s new Titan X).
The landscape, heavily inspired by Scotland’s Isle of Skye, simply looks amazing:

More importantly, Epic didn’t leave it at just showing the cinematic (and announcing UE4 being availiable for free from now on); they, or more specifically Senior VFX Artist Francois Antoine, Lead Gameplay Programmer James Golding and Senior Character Technical Director Chris Evans also did a whole 1h in-depth session about many of the technical challenges that went into creating this huge 16×16 km (!) terrain and how they went to solve them. I’ll embed the Youtube recording at the end of the article.

Besides heavy use of LOD & streaming techniques, topics covered included asset creation through photogrammetry, lighting technology, flora & fauna placement, character development and more.

Delighting

Since many assets captured on location were huge rocks, the team was completely dependent on the lighting that was available when photographing. Interestingly enough, the team developed its own Delighting approach for removing any directional light from the photogrammetric mesh’s textures by recreating the light scene through HDRi Lightprobes in Maya and rendering what Francois Antoine calls a “delighting texture” – which enables them to create a pure diffuse albedo map without any lighting artefacts – the foundation for a true PBR approach.
Here’s a short extract from Antoine’s presentation (courtesy of Francois Antoine / Epic Games):

Environment lighting

As mentioned, the scene makes heavy use of LOD meshes, varying from a 115k polygon “hero-tree” down to 32-polygon billboard-based trees.
Using Depth-Offset for each of the billboard Pixels, a convincing lighting and raytraced shadowing could be achieved (gif):

The mighty Distance Field rendering technology which made its debut in one of the recent versions of UE4, also came to show off its benefits by using it for Distance Field Ambient Occlusion, enabling gorgeous screenspace-independent soft shadowing (gif):

So to celebrate the beauty of the HUGE environment Epic’s team put together in about 2 months (and to shorten the waiting time for it to be availiable in the UE4 marketplace), I created some looped GIFs of scenes showed in the talk (about 18 MB of GIF goodness) – Click to view in full size. Enjoy!

And finally, here’s the whole GDC Session for you to geek into:

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