Real-Time Skies: Theory and Practice

Real-Time Skies: Theory and Practice

3d artist Bryan Adams talked about the tools and techniques, which help him to build realistic skyboxes for his UE4 scenes.

3d artist Bryan Adams talked about the tools and techniques, which help him to build realistic skyboxes for his UE4 scenes.


Hello! My name is Bryan Adams, and I’m a 23-year-old from the distant land of New Zealand. I grew up in the South Island surrounded by farmland, beautiful mountains and amazing skies. I’ve been studying for 7 years in Animation, VFX, 3D modeling and I’m now focussing on Game Development. My years of study have given me plenty of opportunities, including working both in NZ and overseas and even teaching. Right now I’m in my last year of a Game Art degree at Media Design School.

I’ve always been a massive environment fan, initially in film and animation and this has progressed into games. It all started about 2 years ago when I met Mike Porter up in Auckland during a casual trip to expand my learning where we discussed future courses. Three months later I attended a Master class taught by Jason Sussman who is a senior environment artist responsible for looking after Mars, Destiny 1 at the time, in which he talked about the specific pipelines and tricks used at Bungie. This was the day I fell in love with environments within games, and since then I’ve been on a journey to to grow my knowledge of UE4.

When I first started off with environments, I was really interested in skyboxes and how they can create a sense of emotion and background story. But I could find very little information specifically about skyboxes until one day I stumbled across a piece of software called Vue created by E-on Software which allowed me to create beautiful static skyboxes.



Now I’m using a powerful plugin for UE4 called Truesky, which allows me to create procedural skyboxes with volumetric clouds and environmental conditions. I love this plugin as it allows me to experiment in realtime without waiting for baking and rendering.



Skyboxes are massive part of where you are, be it on Earth, on Mars, or even Concord – Longbow (Halo 4). Whether you realize it or not, the sky tells you something about your world and its atmosphere, and there are a lot of factors to consider when designing a skybox.

Some of the major elements I think about when working on a new skybox are time, location, story, animation and emotion. The time of day is, of course, a big part of any skybox, but with real-time skyboxes, it’s also equally important to consider how the sky changes as time progresses. The location is also important, as depending on where you are there will be different environmental effects at play. Take for example if you’re near the sea on a windy day – you may have a haze out to sea which blends and adds fall off to the lighting. The next thing to consider is story – what is the story behind the environment, what does a general day look like in the location, is there a special event happening, like a sun being kept alive, such as in Halo 4’s Solace map. Animation is important as it adds life to the scene and makes it feel more real to the senses – you may be in space so you can’t directly relate to the setting, but having moving satellites or a comet fly past occasionally can help the player to relate to the location more, and it helps tie in what your trying to achieve. Last but not least is emotion – if a player is looking towards the horizon, what do you want them to feel? Peaceful, awed, terrified?

Rick Knox has a great breakdown on the work he did for Halo 4, which I highly recommend for people interested in skyboxes. Rick shows the individual pieces used to create the background and skybox for LongBow, and it was very inspirational for me when I first saw it.

Rick Knox

How do you make realtime skyboxes in UE4?


I use a plugin called TrueSky for UE4 to create realtime skyboxes, which is a great tool and feels very natural if you have experience with tools like Vue.

This is a very simple example of a skybox created in Truesky to show how to set up complex volumetric clouds, while keeping to a particular aesthetic. With this example, I’ve used World Machine as a base for the environment and the Truesky plugin to take over the original skybox. I’ve also hooked up the directional lights to the plugin to simulate the Sun and Moon.

To start off with, I have a semi blank slate made up of a basic water plane and simple mesh from World Machine.

The first thing I often add is a bit of cloud density so I have more to work with.

It’s very easy in Truesky to change the time of day, and in this example I’ve set the time to around 6:30am to to give the clouds more colour.

To break up some of the uniformity and big shapes, you can change the cloud density and add some worley noise. This creates a much more natural flow, and there are many other settings in Truesky that can be tweaked to make a more realistic looking skybox.

Here’s a close-up view of the clouds, and as you can see this already looks quite natural.


Lighting is an important part of working on a skybox. Normally, I will turn off texture streaming in UE4 and create a grey pass so I can focus purely on the lighting. This helps me create the right time of day and after this I can progress onto the clouds. Some of the important things I look at are the type of cloud, coverage, atmospheric lighting, ambient reflections/lighting on the clouds, extinction rate, secondary layers and movement. Then when it’s all done, I turn back on texture streaming, and I can use a post processing volume to tweak particular values to finish.With static skyboxes, I always use temperature to achieve a more realistic colour, and then I rely on post processing to allow me to fine tune the values to get the results I want.


How do you add that artistic touch into this element of the scene?

I find movement is an important element that people often forget. By combining foliage and things like cloud or environmental movement, this can create more of a sense of reality, and like the world is alive. Also having secondary actors in the background, such as animals/creatures, cities or some form of movement, adds depth, size and story to the scene.

There are a number of different ways to add that extra artistic touch to a scene, and one of the best references can be to look at works from people you find inspirational. When I was younger I would always look at the sky, and some days we were lucky enough to have North-Westerly winds which can create some crazy colours and patterns. You know, the kind of thing you’d look at in a movie and think that it wouldn’t be real? I get the same feeling in some games – I love Bungies environments and skyboxes, ever since the first Halo to Destiny 2, and I think their skyboxes contribute so much to the story and the experience. Finding good inspirations that push you to try new things is incredibly important, and some of my main inspirations are Ryan Watkins, Mukul Soman, Tu Bsi, Gökhan Karadayı and Rick Knox.

I would like to thank to Brad Allen and Jason Sussman for teaching me and putting me on this amazing path.

Note: TrueSky is available for Unity and Unreal Engine

Bryan Adams, 3D Environment Artist

Interview conducted by Kirill Tokarev

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    Real-Time Skies: Theory and Practice