Tessellation: What it is and its role in Metro, Stalker, and other games

Contents:

• What is tessellation
• The purpose of tessellation in computer graphics
• Types of tessellation
• Games with a high level of realism in tessellation: examples
• Advantages and disadvantages of tessellation: is it worth using?
• Results

While playing games with high-quality graphics, players can observe magnificent rock formations, clear footprints on the snow, raised seams on the characters' clothes, and many other vivid details. All of these elements are the result of the use of tessellation, which is often present in the settings of modern video games.

In this text, we will take a detailed look at the concept of tessellation, its importance in the world of 3D graphics, its various types, as well as examples of its application in popular video games.

Contents

• What is Tessellation
• Tessellation in computer graphics is the process of breaking surfaces into smaller elements, which allows for the creation of more detailed and complex images. This method makes it possible to improve the quality of rendering, making objects more realistic by increasing the level of detail and accuracy. Tessellation also allows for more efficient management of graphics resources, as it allows the level of detail to be adapted based on camera distance or other factors. This process therefore plays a key role in creating visually appealing and performant graphics in video games and other digital applications.
• Types of Tessellation
• Games that implement a high degree of realistic tessellation demonstrate amazing levels of detail and visual verisimilitude. Such projects include:

  1. **The Elder Scrolls V: Skyrim** - in this game, the expansion, known as the «Skyrim Special Edition», includes enhanced textures and improved models, which allows for an impressive level of detail in the landscape and objects.

  2. **Cyberpunk 2077** - This project stands out not only for its open world, but also for its use of tessellation technology, which gives the environment and characters realistic shapes and textures.

  3. **Battlefield V** - in this game, tessellation is used to create detailed objects, such as buildings and weapons, which significantly increases the level of immersion in the gameplay.

  4. **Unreal Engine 4** - although this is not a game, but a game engine, many projects based on it use tessellation to create photorealistic graphics and complex surfaces.

  5. **Call of Duty: Modern Warfare** - In this franchise, tessellation is used to enhance visuals and textures, making combat scenes more immersive and realistic.

  These examples highlight how tessellation technologies can significantly improve the graphical quality and overall atmosphere of modern video games.

• The appropriateness of using tessellation must be considered, weighing its advantages and disadvantages.

  Among the positive aspects, tessellation allows for a significantly higher level of detail in objects in graphics. This makes images more realistic and appealing to the eye. In addition, this technique can contribute to more efficient use of GPU resources, as it allows the number of polygons to be dynamically adjusted depending on the distance to the camera.

  However, there are also some negative aspects. Using tessellation can lead to increased system load, which in turn can negatively impact performance, especially on less powerful devices. There is also a risk of excessive detail, which can lead to unnecessary complexity of visualization and difficulty in perception.

  Ultimately, the decision to use tessellation should be made taking into account the specific conditions and objectives of the project.

What is tessellation

Tessellation is one of the most important technologies in the field of modern computer graphic design. It allows you to transform flat surfaces into volumetric forms and introduce a huge amount of detail without resorting to using millions of polygons.

Tessellation allows you to divide a quadrilateral into two triangles, and then from these two form four, eight, sixteen triangles, and so on, without limitation. As a result, the initially existing polygons are converted into additional triangles (but not into new polygons), which makes the low-polygon model more complex and detailed.

However, regardless of how exactly the object's polygon is represented - as just a couple or hundreds of triangles - the tessellation process itself does not increase Object detail. Dents and bumps on its surface will only appear if there is data showing the location of the fine mesh vertices. This typically involves the use of bump mapping, implemented through parallax or displacement maps. Displacement maps are particularly popular these days, as, when combined with tessellation, they create the illusion of volume even in flat areas.

A prime example is the Heaven benchmark from Unigine. Even though it was released quite a while ago, this test clearly shows how the final image changes when using this method compared to not using it.

Tessellation support was first implemented in the ATI Radeon 8500 graphics card in 2001 and was called TruForm. The main feature of this technology was the ability to process triangles with a variable level of detail. At that time, various interpolation methods for vertices and normals were available to users, including linear and quadratic interpolation for normals, as well as cubic interpolation for vertices.

Although developers were able to easily implement this technology into existing rendering systems, it was not widely adopted in the industry due to a number of limitations. One of the problems was the gaps that appeared during the interpolation process between polygons. In addition, there was no support for bump maps, and there was no ability to flexibly modify the geometry.

Tessellation gained popularity with the launch of DirectX 11 in the late 2000s. We will discuss this in more detail later.

The purpose of tessellation in computer graphics

The main purpose of tessellation is to improve the detail of both the environment and characters without increasing the number of original polygons. Here are some of the key benefits of this technology.

• Complex surfaces, such as landscapes, bodies of water, and textiles, become more realistic and three-dimensional thanks to carefully crafted fine details.

• Tessellation helps avoid sharp transitions in curves, which is sometimes essential for accurately rendering footprints in snow or sand.

• During tessellation, the level of detail of objects changes dynamically depending on the distance of the player's camera.

Types of Tessellation

Tessellation methods are largely determined by the specific area of ​​use and the skills of the developer.

The term "surface subdivision" refers to the process of dividing the surface into individual segments. After this division, the structure of the model remains stable, regardless of the conditions. This category includes models that utilize the Subdivision Surface feature, which significantly increases the polygon count in the mesh. Static tessellation is most commonly seen in 3D modeling applications such as Blender, Maya, Cinema 4D, and others. In such programs, image and animation rendering is typically performed offline rather than in real-time. Modern video games make extensive use of a method in which a model's polygon count varies depending on real-time conditions. This change primarily depends on the player's viewing angle or the distance between the object and the in-game camera. The GPU or shader analyzes the geometry presented on the screen and determines how many additional triangles need to be generated at any given moment. It should be emphasized that the geometry density in this context changes automatically depending on the distance. Preparing models with different levels of detail (LODs) is optional, except for characters, mobile game development, or environments where high optimization is essential. Dynamic tessellation is supported in game engines such as Unity, Unreal Engine 4 and 5 (the latest version uses Nanite technology), CryEngine, Unigine, and other platforms focused on creating realistic 3D graphics. Unlike dynamic tessellation, hardware tessellation does not rely on game engines, but is implemented directly in video cards via graphics APIs such as DirectX 11, DirectX 12, OpenGL 4, and Vulkan. This is achieved using specialized programmable shaders, the names of which may vary depending on the specific API. For example, in DirectX 11 and 12, the tessellation process is divided into three main stages: the Hull Shader, the Tessellator, and the Domain Shader. Although the stages are essentially the same across APIs, they differ only in their names and code syntax.

Hardware tessellation is used in both games developed with well-known game engines and in projects using custom technologies from creators, such as The Witcher 3: Wild Hunt, Metro Exodus, and Far Cry 4. Thanks to the use of programmable shaders, this method is highly flexible and universal, allowing it to be implemented in a variety of game engines. However, it should be noted that this approach exclusively utilizes the GPU, which may result in reduced performance on less powerful graphics cards.

Please note: Starting in 2024, Epic Games has announced its intention to discontinue support for hardware tessellation in Unreal Engine 5. Cross-platform support for Nanite technology will instead be prioritized. However, if developers decide to integrate this technology themselves, the company will offer some limited assistance.

Games with a High Level of Realism in Tessellation: Examples

Tessellation in The Witcher 3: Wild Hunt adds a slight degree of volume to environmental objects such as roads, terrain, and walls when viewed close up. Users can adjust this setting in the Terrain Quality section. However, in practice, the impact of this effect is minor and is best seen with various modifications.

The game also includes advanced NVIDIA Hairworks technology, which is responsible for tessellation of hair, fur, and fur, ensuring their detailed display at the level of individual strands. However, many players have noticed issues with their characters' hairstyles not displaying correctly.

In Metro Exodus Tessellation, combined with ray tracing, significantly changes the appearance of game locations, giving walls, objects, and the surrounding world additional relief. This creates a deeper sense of realism in the environment, which is especially important for a first-person shooter, where players often observe details of objects in close proximity.

Digital Foundry correspondents emphasized that in this regard, the PC version of the game looked significantly better compared to the Xbox One X, which lacked the effect of volumetric surfaces.

In Battlefield 5, tessellation technology not only realistically reproduces the relief of stationary surfaces, but also displays character footprints, as well as tire and track prints, which adapt depending on changes in gameplay. It is also used to visualize craters formed by explosions. Similar to how it is implemented in The Witcher, the volumetric relief effect can be adjusted in the «Terrain Quality» section.

In addition to vegetation tessellation, this game also used pixel-level displacement mapping. This technique allowed tree trunks to appear three-dimensional without the need for tessellation. You can see this method implemented in gameplay in the video below.

The game's story takes place against the backdrop of the picturesque landscapes of the Himalayas, which makes tessellation in Far Cry 4 focused on enhancing the quality of the environment - including landscapes, mountain ranges, trees, and even animal fur, thanks to the NVIDIA Hairworks technology, which was mentioned earlier.

Advantages and Disadvantages of Tessellation: Is It Worth Using?

Using tessellation significantly improves the visual perception of graphics in video games, but requires careful evaluation and a thoughtful approach.

Games are seeing significant improvements in visual quality. Increasing the number of triangles, combined with the use of displacement maps, makes game worlds more believable. Although this is only a simulation, these surfaces provide higher-quality rendering of cast shadows, unlike standard objects using bump or normal maps, where the surface is essentially flat.

Modern development tools provide support for tessellation. Popular game engines and modern graphics APIs that utilize hardware techniques allow developers to integrate this technology into games with minimal effort.

Incorrect display of the effect. In discussions about various video games, one can often hear complaints about errors that appear when tessellation is enabled. In some situations, it even worsens the gameplay.

Performance drop. As the detail level increases, the load on the GPU increases. Therefore, on less powerful graphics cards, a decrease in frame rate may be observed. However, it's important to note that this also depends on how well the game is optimized for specific graphics card models. For example, Shadow of the Tomb Raider is well adapted for NVIDIA graphics cards, and therefore activating tessellation has little impact on performance.

Summary

Tessellation is a significant tool in the field of 3D graphics, allowing for the creation of more volumetric and realistic images of flat models using special displacement maps. This method is widely used in games with large budgets, where it helps to increase the detail of both the environment, landscape, and characters.

While the technology has many advantages, its successful implementation and optimization require a careful approach, especially when dealing with systems with limited characteristics. In certain situations, the developer will need to create several levels of customization to ensure that as many users as possible can enjoy a detailed game environment.

It is equally important to avoid overusing tessellation by adjusting its level. While a pavement covered with large stones may look impressive in the context of demo materials, in gameplay it is difficult to imagine a character who could comfortably move along such a surface. Thus, when implementing this technology, the developer should strive to balance between realism, performance, and reasonable expectations.