Replicating the Sky from a Photograph using trueSKY

For this weeks blog, I am going to be replicating the sky from a picture that I took near our office in Liverpool.

As you can see, the image I’ve selected is not the easiest to recreate. I got very lucky when I went out to take pictures, as the weather here is usually just a shade of grey. Within the photo are multiple cloud types, spread all over the image. Regardless, I though it would be a good challenge, and a great way to show trueSKY’s different features. Please be aware that trueSKY is not designed to replicate the identical shape of an individual cloud, or photograph. trueSKY is designed to create types of clouds, with their own shape and sizes. Creating a scene with identically shaped clouds is not recommended, but with some effort it is not impossible.

Planning

For an accurate replication, I need to plan out the different sections of the Clouds that I am going to produce, so I can split them into layers.  In my opinion, this image  appears to have 3 different layers.

The first layer is for the larger, darker clouds towards the bottom of the photo.  I would say these are part of the Cumulus cloud type, possibly a small Cumulus Congestus.

The second layer is for the clouds closer to the camera, what I would call Cumulus Fractus, as their shape is ragged and broken up. These clouds are quite small but there is plenty of noise surrounding them.

The third and final layer I am going to create is for the clouds much higher in the atmosphere, where they appear almost 2D the sky. These appear like Cirrocumulus clouds to me.

Here is an image defining what I believe to be the different clouds present in the photograph.

But before we create the clouds, I am going to make sure my Sun and Sky look correct.

Sun and Sky

This photograph was taken on the 29th August 2019 at 14:52 at the Latitude and Longitude “52.93822, “-2.888733”. Inputting this data is quick and easy, and results in the sun being in the correct position in the Sky. I am going to increase the diameter of the Sun slightly, to get the stronger bloom that is in the photograph. The sky’s colour looks similar enough for now, I can readjust these later if needed. I will however use trueSKY water to simply make a large body of water below the sky, similar to the photograph.

 

Replicating Clouds

For this weeks tutorial, I am not going to go over every value I have changed, as it would take too much time. trueSKY is not designed for image replication, as you can’t adjust individual cloud shape freely, so a lot of the clouds were carefully placed into the scene. I ended up with a total of 5 Cloud Layers, some were used to add just a few clouds to the replication.

Cumulus Congestus

The Humilis cloud layer is very large, so the first thing I am going to do is increase the volume width. This allows for larger clouds to be produced. I then enabled override wind, allowing me to position the layer. In fact, for all my layers I will enable Override Wind. This will allow me to accurately place each cloud layer in my scene. Using this, I moved the clouds further back from the camera.  Now that I felt they were in the correct position, I could then increase the height and density. This gives it a darker base as less light can travel through the cloud.

Cumulus Fractus

These are the smaller clouds in the Sky. In the photograph, there are only a few clouds nearby, but they have very different characteristics. Because of this, I am going to split this layer into 2, to allow me to create different cloud types. The first layer is for the large cloud to the left of the screen. This cloud is quite dense, due to the darkened base,  but still diffuse enough to be bright in areas. I increased the transition layer value to allow the cloud to be a similar thickness throughout, instead of being much larger on the bottom.

I am now going to add the small cloud covering the Sun. This layer takes similar parameters to the previous layer. However, this cloud is very diffuse, as all of the Sun’s light is passing through the cloud. These clouds are also not very dense. I adjusted the Worley scale to make sure that there were multiple smaller clouds opposed to a select number of large ones.

 

Cirrocumulus

The final layer is a thin, whispy, translucent layer that is dotted all around the scene. For this, I made sure to set the cloud base high, with a low layer height. Limiting the maximum height of these clouds is important. Next, I set the Max density to 0.2 This made it so my clouds were very weak, exactly what I wanted. Decreasing the Base, Transition and upper layer helped keep the cloud as thin as possible, but I did not change them too much. When adjust the Worley Values, I increased the Noise while decreasing the scale. This allowed me to produce clouds that appear as a small sheet, which I can then position into the side of my scene.

Diffusivity was also increased, and so was persistence. Persistence is not recommended all the time, but for thin clouds like these it helps break them up to look more unique. Finally, I set amplitude to 5. This Cirrostratus cloud goes nicely into the side of my scene.

 

Final Cloud Adjustments

I decided to add another layer of clouds, similar to Cirrostratus. This layer would be similar, but much more broken up, to “fill in the gaps”. I believe this makes the scene more busy, which was needed in places.

For settings on my trueSkyActorObject, I surprisingly did not change too many settings. Ignoring the obvious changes to resolution and texture sizes, I have only adjusted the lighting settings. Extinction is up to 10, while indirect lighting is up to 2.2. I have done this to make the darkened base stand out more. As apposed to our last cloud tutorial, all of these clouds were made with the Grid integration method.

 

Result

 

 

As I said initially, this was a difficult challenge for trueSKY to pull off, as perfect replication is not recommend. Regardless, I believe this result is a great proof of concept for the different potentials of trueSKY. Looking at the comparison again I can see a multitude of improvements such as the Sky’s colour is too rich, or some clouds are too diffuse. Unfortunately, I did not have forever.

While creating these clouds, I thought of many different ideas on how to improve our cloud creation. This challenge will hopefully lead to new and exiting features! If you would like to learn more specifics on what I have done, or need help with your own projects, you can email contact@simul.co or click here to join our Slack Channel.

Documentation

We recently talked about updating our documentation, but we failed to grasp the time frame that would be required for what we desire. Because of this, we will be making our documentation changes live next week. We believe getting updated documentation out as soon as possible will help you the most, and we will continue to work on it through the coming months. Although there may be some information that is lacking in places, please bare with us. We have plans for detailed, written tutorials on different types of clouds formations and skylines (similar to my blog posts), along with downloadable sequences to apply to your own scene. Also, please let us know what you would like to see! I will be creating a dedicated section on our Slack page for documentation requests and opinions.

Showcase

This week we are taking a look at Exo One! Created by Exbleative, Exo One is an interplanetary, gravity-defying journey through space and time! Take control of an alien craft, capable of manipulating gravity as you traverse unique alien landscapes. Take to the skies or keep to the ground, with no challenges or enemies, you are free to explore at your own pace. Exo One uses trueSKY to create some amazing alien planets, something we don’t often see! Take a look below!


Exo One is releasing this year! So make sure to add it to your wish list on Steam. You can also check out some gameplay here!

 

Thanks again for taking the time to read our blog. This weeks blog was decided by a vote over in our community Slack channel. If you have an idea of what you would like to see next, come and vote! Click here to join our Slack Channel!