trueSKY for Unreal Engine 4

Before you begin

Please first ensure that trueSKY supports the platforms and API’s that you need.

x64 (D3D11) x64 (D3D12) x64 (Vulkan) x64 (OpenGL) PS4 Xbox One (D3D11) x64 (D3D12) Switch OSX
x x x

Getting started

Installing the Plugin

For binary installations of Unreal Engine, binary trueSKY plugin installers are available from https://simul.co/download. For other versions, or if you have a version of Unreal Engine built from source, you will need to build the plugin. For GitHub/Engine Source Integration, check this page.

Important The stock binary version of Unreal does not deploy trueSKY files when packaging a project. You will see a black sky unless you deploy these files. See Deployment for instructions.

Running the Plugin

When you run the UE4 editor, the trueSKY plugin should be enabled by default. If not, open up the Plugin Configurator for Unreal Engine (from the menu bar: Edit->Plugins). In the plugin configuration window and type “trueSKY” into the search box to find the plugin; check the “Enabled” box to enable it.

alt text

alt text

If you had to change the “Enabled” setting from disabled to enabled (or vice versa), you’ll need to restart the editor for the change to take effect, as with all editor plugin changes.

Adding trueSKY to Your Level


Adding the trueSKY Sequence Actor

The trueSKY Sequence Actor is the primary way to access and interact with the trueSKY renderer and its rendered sky sequence within Unreal Engine 4. You can add this actor from the standard “Place” sidebar in the editor, choosing “All Classes”, typing “trueSKY”, and choosing the “True Sky Sequence Actor” to drag into your scene, or you can use this handy little shortcut:

Once you have the True Sky Sequence Actor in your scene, choose it from “World Outliner” window. Then, to customize it, open up the “Details” window/sidebar; set the reference to an existing TrueSky Sequence Asset in the “Active Sequence” dropdown. By default, there are two sample sequences you can instantly check and see the results for yourself:

Creating New Sky Sequences

To create a new TrueSkySequence asset, go to the “Content Browser” window. Press “New Asset” button (or do a right mouse click inside the window) to open an asset selection window. Choose “Miscellaneous / trueSKY Sequence Asset”. A new asset will be created. Now you can rename/save/delete it.

In the World Outliner, select your trueSKY sequence actor, and in the Details panel, set its Active Sequence to be the newly created asset:

To edit the TrueSkySequence asset just double-click on it:

This will open up the True Sky Sequence Editor:

Creating and Configuring a Sky Sequence

Multiple Sequence Actors and Transitions

TrueSKY supports three different modes of update. In Game-Time mode, it takes a specified amount of time in game hours. The weather won’t change if game time does not. Fixed Intervals mode is similar, only there’s a specific number of interpolated intervals between any two keyframes. You can use this mode to create more detailed transitions around sunrise/sunset for example.

If you’re using real-time transition, you can adjust the Interval in seconds to determine how quickly the change takes place.


In all cases, the number of Subdivisions controls how finely the interpolation is performed. It’s the number of intermediate steps between keyframes (for Fixed Intervales), or in the Game Time or Real Time period specified.


Use the Blueprint function GetProfilingText to get GPU and CPU timing numbers for trueSKY as a tree. trueSKY performance is highly dependent on your choice of settings. Once you have good settings for a given target hardware setup, performance will be consistent - i.e. there won’t be spikes or hitches. For PC, you may want to make some of these settings controllable for the end user. For console hardware, it is usually best to choose the settings based on your target GPU time for skies, then lock them down.

Sequence Actor Settings

Further Information

Next: Tutorial