Changes

UE4 has some greate physically-based rendering in its main pipeline, which is a really good fit for our approach. You can enable trueSKY by installing the plugin, then adding a trueSKY Sequence Actor to the Level. Then you assign a trueSKY Asset to the Actor. You can change assets at any time, either instantly, or gradually with real-time updates. The assets themselves have keyframes, but you can also modify them dynamically. Blueprint allows you to script weather changes based on gameplay states, so you can make things fully dynamic, changing either the entire asset, or modifying keyframe values for gradual dynamic weather changes.

How do layers work with the clouds?

In trueSKY up till now (version 4.1) we’ve had two layers, one 2D cloud layer at high altitude (e.g. cirrus clouds), and a 3D layer. TrueSKY 4.2 (released September 2017, but available for testing now) represents a departure: now we have multiple 3D cloud layers of different types – there’s no set limit – that can overlap, covering a 600km visible volume around the camera. In 4.2, there are no 2D cloud layers – we’ve found a way to render cirrus and other thin, high-altitude cloud formations volumetrically. And instead of repeating horizontally, you can have completely different weather in different parts of your game-world: you can have a clear sky overhead, but a gathering storm in the distance. But more than that, you see that storm building as you approach it, seamlessly transitioning from one state to the other.

Using the sky for a game

TrueSKY can provide weather for any type of game where you can see the sky. One thing we’re working towards in the 4.2 release is the idea that, when the weather is changing very slowly, the CPU and GPU usage can be very minimal: almost as low as using a static texture. So you can use it as a default background without too much worrying about performance, and introduce dynamic behaviour where needed.