Creating a Rock Mine with RTGI and Unreal Engine 4

Introduction

Good Day. My name is Yongjae Choe. I'm currently working as a 4-year Junior Environment Artist in Korea. I studied 3D animation in college and I was very interested in cinematics, but I also loved games so much. After graduation, I changed my course to games and became a game developer. I experienced the mobile MMORPG Legend of Mir, and the open-world FPS project, I am now working on Project Eve.

In Korea, the development of mobile games is the mainstream, but I personally prefer single-player games to online games. I am satisfied with the current project. Also, I am very interested in lighting, so looking forward to the day I can work as a Lighting Artist.

The projects I make for myself are small because I also have the company's duties to take care of. The Rock Mine is also a small piece of work, but I am happy to have the opportunity to talk about it with you.

Beginning

I'm using 3 monitors in my company, and I always have ArtStation shown on one monitor. When I take a break, I swim in the sea of art and collect concepts that I would like to make once. The Rock Mine was also based on the art that I found like that. Thanks again to Jordan Grimmer for his great concept.

As mentioned earlier, since I am busy enough for my company's work, large-scale works take a lot of time, so Mine, which can be finished with 3 rocks and a few wooden sticks, was a perfect reference. I think that work fatigue is also a very important factor in creating works. If you start working with too complicated projects, you will quickly become tired, and if you feel tired early the quality will be compromised, and you could not fully bring out your skills. Just as song selection is very important for an audition, it is also important to choose a reference that fits the current situation.

I originally looked for a large number of references before starting the work, but at the time I had already had a good concept image and the number of props to be made was small, so I didn't need a lot of references.

Props

The reason I did this work because rock sculpting practice was my main purpose, so I invested more time in this than in anything else. In past experiences, there weren't many rocks needed to construct a cave or cliff. I thought to need three kinds of rocks, so I made 3 pieces: a box shape rock, a round rock, and a versatile rock that can be used anywhere.

A good shape to use when dressing the set is a rock in the form of a terrace. Because it is flat, the character runs around on it easily. 

However, if a cave is composed of only complex-shaped rocks, the rhythm of strength and weakness can be broken, resulting in a very messy image. Usually, it is good to represent cave walls with rounded and flat rocks without angles. The overall structure is made of stones with soft shapes, and a rhythm is created by inserting rocks with terrace form rock at the required points.

I used TrimDynamic, ClayTubes, DamStandard, and TrimSmoothBorder brushes for rock-sculpting and finished with alpha texture.

The alpha texture of various cracks and rock textures greatly reduces the work time and improves the finish but If you overdo it, you can get a very dirty Normal texture. I usually put the big cracks in ZBrush and put the small details in Substance. If you make all the small details in the sculpting stage, it going to be cumbersome to modify it on the texturing stage.

If the rock shape is complicated, the longer the sculpting time will be. The square shape rock took 5 days. The columnar rock was finished in just 2 hours.

In the past, I used Substance Painter to stack single color layers one by one to complete the rock texture, but recently I use scan textures from Megascans or Substance Source. Much more effective, much faster.

There are so many useful scan rock textures in the Substance Source and Megascans. In fact, it's common to use tile textures for AAA games. We live in a really convenient world.

If you are texturing with Substance Painter, it is recommended to change the default environment setting. Because the panorama is basically blue tones, it is difficult to see the exact values, achromatic environment is fine, I recommend Tomoko Studio. In addition, setting the tone mapping and SRGB settings as follows will result in a viewport environment similar to Unreal's ACES color definition values.

Of course, there is a way to match the viewport environment of Unreal and Substance Painter 99% the same, but I'm satisfied with this setting.

When it came to the wood, I only needed a few sticks which didn't have to be detailed, so low poly was sufficient enough. The texturing was done in 1 hour.

A UV tip – if you have a texture that has a wood-like orientation, you should make sure that the UVs are facing in the same direction. Otherwise, you will need two layers of the same texture, horizontal and vertical.

Lighting

Lighting is a key part to create a visual by setting the light and the fog. This scene is not intended to be playable, only visually appealing. It's 100% real-time and Ray-Traced.

The RTGI is very heavy, but it shows a really realistic visual. Ray tracing is already being used in many games and I think most of the games will be using them in a few years.

Unreal engine's ray tracing can be used with older graphics cards such as 1070, 1080, but great framerate is not guaranteed. If you have an Nvidia RTX 2000 graphics card or higher, you can find DLSS on NVIDIA official website or Unreal Marketplace.

DLSS (Deep Learning Super Sampling) is an artificial intelligence-based anti-aliasing + upscaling technology that is currently used by many games. It greatly increases the framerate when using ray-tracing.

It doesn't need as much lighting during the day as it does at night. GI is also ray-traced and automatically calculated to some extent, so there is no need for light baking.

I use color temperature for daylights like sunlight or realistic light sources like lights and fluorescent lights because it is a color that actually exists in reality, so you can find a more familiar and natural color.

This is the only daylight added. This light alone creates ray-traced indirect light, so the expression of the emphasized part in the center is satisfactory. But the more it goes to the outside, the more it becomes black. I didn't want the image to come out too dark. To fix this, I intentionally added a Point Light and a Spot Light.

I have added a Spot Light to increase the brightness of the rocks around the entrance of the mine. In reality, it may be physically wrong because there is no light source other than sunlight in the sky. But I thought it would be nice if the contrast of the stone could be seen more clearly in the center where the gaze would be concentrated.

Next, the wood stick's silhouette is weak because it doesn't receive any light. To fix this, I made a line light by adding 3 point lights. It doesn't fit the reality but the wooden pillars occupy a small area of the screen composition, and the pillar-shaped props look very good when the silhouette is emphasized. I deliberately dropped the Roughness of the wood texture to make it shinier and wetter. This is the way I like, and if you moisten it a little more than it actually is, it will receive a better light.

Finally, the entire screen became a single solid color tone due to the orange-toned light source, red-toned wood, and sand, which made the composition less interesting. To fix this, I added a few blue lights and made the color of the fog blue to separate the tones. It was a small addition, but it worked very well.

I avoided excessively dark scenes. Each person has a different brightness of the monitor, so you need to be careful that your image isn't too dark. If you have finished working on making a dark place, a good idea to look at the monitor in a bright place and also put the image on your mobile phone.

Post-Processing

Unreal's post-process is very strong. You can create various cinematic visuals through the function of Color Gliding. If you are using ray tracing, the following options are enabled:

Ray tracing AO is more accurate than SSAO.

Real-time GI is the most important factor. There are two methods, Brute Force and Final Gather. Brute Force is heavier but more accurate. You can control GI color or intensity in post-process volume or adjust the Indirect Lighting Intensity value on the light detail.

There are more, Ray Tracing Reflections and Ray Tracing Translucency, but I haven't used them for this work. Translucency uses huge resources, so be careful if your own hardware performance is insufficient.

Fog

Unreal Fogsheet is a great way to conveniently draw dynamic scenes. Because it is blueprinted, everything you need, such as color, transparency, noise size, speed, direction, etc., can be adjusted. However, because it is just a single plan, not a volume, only use the Far Away view.

Epic provides this Fogsheet by default. Thanks, Epic.

Conclusion

Light is an area where the correct answer is ambiguous, either you like it or hate it. Every person has different opinions even about shadows.

Experience various works of art, many photos, and games, and check what light gives you a good feeling and a bad feeling. Try to imitate the light that gives you a good feeling and make it your own, it will someday become your own special lighting.

Believe in your senses and have a lot of visual experiences for objectivity. Thank you for reading.

Yongjae Choe, 3D Environment Artist

Interview conducted by Arti Sergeev