Environment artist Timothy Dries talked about the production of Absolute Zero scene in UE4. A great look into the creation and lighting of complex natural caves.
A personal goal of mine on every project is to learn or push the limits of what I can do in my projects and what software I use, and I really did push myself in this scene. I used world machine for the first time, spent a lot of time in Zbrush (out of my comfort zone) made some cool looking water and ice using shader techniques that I hadn’t used before. So it was challenging to say the least, but I really liked it, all the research and experimental stuff.
You can see more of the different things I tried and made for this scene in the movie via this link:
Reference and inspiration
For reference I used all kinds of caves, and was initially drawn to Icelandic caves, some of the caves over there have hexagon shaped rocks all over the wall and floor which look really cool so that’s where I got my initial inspiration from. But as I got further in adding bits to the scene the feedback that I got was that the hexagonal shaped rocks would look to unfamiliar to most people so I decided to push them back and have them not take the centre of attention. I also really liked the look of small glow worms lighting up the cave as seen on the right of the reference board. So I went on and made a special particle which dims the particles slowly before letting them emit light again.
My full reference board can be seen over here.
Sculpting the assets
The scene itself only consist of 5 modular meshes and 2 small unique little meshes, the bow and quiver. I made the wall piece with modularity in mind, meaning that every side must have its role in placement and covering up the repeating patterns.
The way that I approached sculpting the rocks on Zbrush was just starting from a simple cube moving the bits of the cube outwards until I got the base shape of a rock going. This took me a couple of iterations and some reference lookup to get where I got in the end. Nothing to fancy here in terms of brushes, I just used a Trim Adaptive and ClayTubes for the rocks and the upstanding ice shard. A combination of move and blob brush was used for the dripping ice. The main thing to keep in mind when sculpting rocks in Zbrush is to be loose, every shape you make can be something you can use, so be a little abstract.
To give the cave itself more of a cave like feeling I also used the dripping ice mesh as stalagmites.
The materials you see here are created in Substance Painter, I baked the Normal, AO, Curvature straight in Substance Painter which is super fast for that stuff, and it still amazes me every time I bake something.
For the materials themselves, nothing to fancy here see more in the upcoming part about textures. A thing I did try that was more experimental and did not make it into the final scene was that I painted on top of the mesh with a particle brush on a new layer with black mask and exported that mask to Unreal to get some water running down from my mesh but only from the parts the particles masked off.
You can see that in the research video:
In the screenshot above you can see the material layers that make up the whole of the materials. On the left side of the image you see is the base mesh without any layers, just using the AO and the normal we previously baked out using Substance’s baker tools. Then it all starts with a base color, I started out with a light greyish color.
Next I added some color variation then I added a tiny bit of extra variation with a lighter color. Next up was handling the cavities where the dirt gathers, as the mesh was looking to flat at this point. So I added another layer using again a darker color. Last but not least it was time to make the edges stand out a bit using a light grey color.
Keep in mind that all of these layers are not what you are looking for straight of the bat, try the different settings of the generators and paint a little bit on top of these if you need to add a little personal touch. The way I approach this is that I add the base layer and all the color differences, balance them out first and then try to give the material some more life by adding dirt in cavities and damaged edges and such.
The ice that is used in this scene took me a couple of iterations to get right, as this was my first time handling a subsurface scattering shader. But after watching and reading a few tutorials and looking at the Unreal documentation this was fairly easy to do actually.
On the left you see the master material and on the right you see the Instance, in which you can control the parameters of the master material. Once you have these guys set up it all comes down to playing with sliders.
The water material used in this scene is something I struggled a little bit with, but as I look back it does its job fairly well, still some room for improvement though. In the above screenshot you can see that I have added some little particle bubbles and a little vapour from where the water is going down a bit.
The coolest thing about making a water shader is that there is a cool node called “Depth fade” this creates the white edge that you see where it touches the other meshes.
The shader setup is actually pretty simple for this kind of water and as with everything I make in the material editor I make everything that I need to adjust later on a parameter as this is nice to tweak materials on the fly without needing to rebuild them.
Lighting this Scene Up
Most of the light is coming from the outside using an directional light, I kept the light at a reasonable high angle because I wanted a clear difference between the darkness of the cave and the exit/campfire part of the cave which meant I had a really nice contrast between light and dark. I did use a couple of fill lights to make the cave less dark and to make more sense of the glow worms that are on the ceiling of the cave itself. The orange light is coming from the particles that emit light by themselves giving the scene a nice feeling of liveliness this is a really neat trick in Particles and really easy to do as well.