Precipitation and Storms with trueSKY

This week we will take a look at creating rain, snow and storms with trueSKY!

Apologies for this late Blog. Busy weeks have resulted in the blog being pushed back – much further than preferred. If this happens again, we may consider making the blog monthly. But for now, we will try get back to bi-weekly. I have also covered lots of topics at the end of the blog, relating to trueSKY moving forward.

Precipitation and Storms

Rain and snow are a great addition to any project. Watching rain-clouds fly past or gentle snow falling down can add a new level of realism and immersion.

For both Unity and Unreal, adding it is easy!


In Unity, it is as easy as  changing a variable.

Just initialize trueSKY in your scene. Then, on a cloud keyframe, set rain Strength to 1.

Now when hit play, you have rain (as long as you are underneath some clouds!).

If you don’t have rain, make sure there are enough clouds, and that you are editing the currently active Keyframe/sequence.

By default, rain is locked to the clouds, and will only be produced if the clouds are of a set density. To change this, adjust the threshold variable.


For Unreal, if all is set up correctly, it should be just as easy. Just adjust the Strength value on a cloud keyframe. However, if there is no rain, there are a few reasons why that could be.

In Unreal we create the rain using a post process material. This means you need a post process in your scene, and to apply trueSKYTranslucent as a post process material.

Make sure you have a the translucent Render Texture applied to your trueSKY Actor as well!

Also, make sure the material is referencing the correct render texture. If you have files copied over to your local content folder, don’t get these confused with the plugin content.

Now, just to be sure, press Play!

One final issue that could be the cause of no rain in your scene, is multiple cloud layers. If you have multiple cloud layers, please apply rain to keyframes on the most recently created layer (the last one in the sky sequencer). Multi-layer precipitation is not something we currently support, although we have been looking into this and have plans moving forward.

Now we have rain, we can customise it in many different ways. One of my preferred ways to use rain is have a low rainfall speed, and really increase the raindrop size. You can see how each raindrop is lit by the trueSKYLight! You can even add your own Cube map to light them. (I made the sky orange so you can see it better)


There is also snow! Make sure to increase the Snowflake size initially, snowflakes take in the colour of their surroundings, so they can be hard to see. In my opinion, the snow usually looks best with a slow fall speed and a high waver.

Make sure to check the trueSKY Actor’s precipitation sections for extra customization.


Storms are used to create lightning. You can create many different things from quick bursts of thin lighting, to  large, radiant strikes which light up the clouds!

Storms are different to keyframes, as you specify the amount of time you wish for them to be active – by dragging across the layer.

There’s lots to experiment with, so please play with the different settings and then show us what you’ve created!


trueSKY 4.23 Plugin has been released for a while now. Over the past few weeks we have had some issues with trying to release new updates, but we believe most of these have been solved – so future updates will not take anywhere near as long! Unreal 4.23 brings lots of amazing features, you can find out more about them here. I am especially excited for the new Chaos Destruction feature!

To add to releases, we are planning to be releasing updates on set dates. This way, we believe we will have more reliable releases with multiple fixes. We will still release hot-fixes if necessary, but for most issues we aim to release around once every two weeks. For our next update, the Unity plugin should finally have a lot of necessary fixes. More information on builds will come soon.


Slack has been used by Simul for a while now, but the more we grow, the more the issues present themselves. One of the main issues is, without an easy way for users search, we end up repeating ourselves. We may also answer a common question to someone in a private chat, meaning nobody else will get that information! Because of this, we are planning on moving to a different community hub in the future. Please let us know about any suggestions you have, and we have already taken into consideration some, but we are aiming for a Q&A online forum –  similar to Unreal Engine’s Answer hub. We will still use the Slack until we have completed a migration to a new platform, so please join and continue the discussions.

Slack users will notice that this blog is not about Performance. Performance was voted as the most requested blog, however as we started to begin, we noticed some issues we would prefer to address before we publish a blog. I don’t want to recommend using setting that don’t work correctly, so we will postpone that until we have had suitable fixes.

Social Media

We are going to try to have more of a presence on social media. The best way we can do this is with your help. Tweet at us, email us, or use Slack to show off your amazing work incorporating trueSKY and we will do what we can to show it off. We have a dedicated YouTube playlist filled with work you have done using trueSKY, and we hope to keep filling it! We’ll be doing our best to post every week, so go like/subscribe/follow on Youtube, Twitter, Facebook!


In our last blog, we mentioned that we would have a rough version of our documentation out. This has been released, and I hope to see lots of requests for documentation pages (there is a Slack page to input requests). Please bare with us initially, as the information may be lacking, but we will make sure it is correct and stays that way. Also, the layout of the pages will also not be were we want it, but that will hopefully change just as quickly. We aim to have tutorial pages on how to use different settings for each feature of trueSKY, from simple clouds to thunderstorms.

I apologise for how long this blog has taken, and hopefully we get right back into routine with the next one!