This was a fairly quick, spare-time exploration of Ultra Dynamic Sky / Weather in Unreal Engine 5.2. It’s a relatively simple scene using assets from Quixel, Unreal and Twinmotion. With UDS the first requirement is to remove all standard lighting and atmosphere components within an Unreal scene, sun/sky, height fog etc., so the plugin-components can work as one integrated system. UDS has hundreds of exposed variables and a large number of presets, which makes set-up extremely fast. Unsurprisingly this scene starts with the ‘rain’ preset.
From the point of view of rendering, this uses Lumen, not hardware ray-tracing. Having compared the two a while back I was impressed by how Lumen treats translucency in particular, which seemed appropriate for both foliage and to some extent surface water. In addition, it’s extremely fast. Lumen is default in UE 5.2 scenes.
As well as particles UDS supports material effects. To do this requires a small amount of editing of Blueprints, but it’s not especially time-consuming or difficult. Before the output component of the blueprint all that’s needed is a (in this instance) wet weather element, which processes base, roughness and normal values. In addition ripples and streaks can be controlled here.
The one issue I had with this scene was the trees. These are Quixel Megascans European Beech and I initially used the foliage painter to provide background density. This however resulted in extreme motion artefacts due to wind movement, which I assume is some conflict between movement vectors and temporal anti-aliasing. I couldn’t resolve this, so instead I hand-placed a couple of hundred trees – a process which only took around 20 minutes. Apart fro this it was a very straightforward scene.
The scene runs in real-time on a Quadro RTX 5000 although I haven’t optimised it. For the cinematic I set TAA samples to 8 – nothing else. Render resolution was 2252 x 944 (2.39:1 at 2048 x 858 times 10% to give a wiggle in After Effects a bit of room to move around). I decided on camera shake in AE just because it’s easier to tweak when the shots are lined up. I also added film-grain (Kodak T320). Render time for the whole cinematic with sub-sampling in UE was around 25 minutes.
I think the metaphor for this kind of test may have changed. Instead of storyboarding in advance, my approach would be more like wandering around a real-world environment with a hand-held camcorder. It’s very refreshing.