Tessellation (Surface Subdivision) Displacement Mapping (texture replacement), displacementmapping

Tessellation (Surface Subdivision) Displacement Mapping (texture replacement), displacementmapping

DirectX 11 Tessellation (Surface Subdivision)-What is Tessellation (Surface Subdivision )? Why does it play such an important role?

With recent discussions on DirectX 11, you may have heard a lot about Tessellation, the biggest new feature of DirectX 11. As a concept, Tessellation (Surface Subdivision) is very straightforward, that is, processing a Polygon into many small fragments. But why is this processing method highly visible? How does it help improve the quality of the game? In this article, we will analyze the reason why Tessellation (Surface Subdivision) can bring profound changes to PC 3D graphics, and explain NVIDIA®GeForce®How GTX 400 series GPUs provide breakthrough Tessellation (Surface Subdivision) performance.

In essence, Tessellation (Surface Subdivision) is a way to break a Polygon into smaller fragments to improve geometric fidelity. For example, if a square is processed and cut along the diagonal line, the square is actually subdivided into two triangles. In itself, Tessellation (Surface Subdivision) cannot improve the half-point fidelity. For example, in a game, it doesn't matter whether a square is rendered into two triangles or two thousand triangles. Only when a new triangle is used to describe new information can Tessellation improve the fidelity.

When a placement texture (left) is applied to a plane, the generated surface (right) shows the height information encoded in the placement texture.

The simplest and most popular method to use a new triangle is the technology called "Displacement Mapping. The replaced texture is a texture that stores the height information. When applied to a certain surface, the texture enables the vertices on the surface to be raised or lowered based on the height information. For example, with a marble slate, graphic artists can "replace" the vertices to create the carving effect. Another popular technology is to apply the replaced textures to the terrain to sculpt bullet pits, valleys, and mountains.

Just like Tessellation,Displacement Mapping)It has been around for a long time. However, it has not become popular until recently. The reason is that to make Displacement ing effective, the surface must be composed of a large number of vertices. Taking marble carving as an example, if a marble block consists of eight vertices, there is no relative replacement between them. A detailed relief can be generated only when there are enough vertices in the basic mesh to depict a new shape. In essence, Displacement Mapping requires Tessellation (Surface Subdivision), and vice versa.

With the advent of DirectX 11, Tessellation (Surface Subdivision) and Displacement Mapping (texture replacement) have finally achieved a perfect combination, and developers have joined this camp. Like Alien. popular games such as Predator and Metro 2033 use Tessellation (Curved Surface Subdivision) to generate a smooth appearance model, the developer Valve and id Software have completed some promising work and applied these technologies to their existing game figures.

When a rough model (left) is processed by Tessellation (Surface Subdivision), a smooth model (intermediate) is generated ). After applying texture placement (right), game players are close to the film-like fidelity.©You have all rights reserved for kenth Scott and id Software. 2008

Because the DirectX 11 Tessellation (Curved Surface Subdivision) pipeline is programmable, it can be used to solve a large number of graphics problems. Let's take a look at the four instances.

Perfect concave & convex texture

In essence, Displacement ing (texture replacement) can be used as a temporary replacement technology for existing concave and convex pasters. For example, normal maps and other current technologies can create the illusion of concave and convex surfaces through better pixel rendering. All these technologies are only effective under specific circumstances, and not all of them are so lifelike when they take effect. The following uses the advanced parallax masking texture in the concave and convex textures as an example. Although it can generate an overlapping geometric illusion, it can only work on the plane and inside the object (see ). True Displacement Mapping does not have these problems and can generate accurate results from all perspectives.

Smoother characters

Without manual input by artists, PN-Triangles can automatically smooth game characters. Both geometric and illumination fidelity can be improved.

The refinement algorithm is another natural partner of Tessellation (Surface Subdivision. The refined algorithm can process rough models. With the help of Tessellation (Surface Subdivision), this algorithm can create a model with smoother appearance. PN-Triangles (N-patches) is a popular instance. The PN-Triangles algorithm converts a low-resolution model to a curved surface, which can then be re-drawn into a mesh composed of Triangles subdivided by high-precision surfaces. In today's games, a large amount of visual illusion that we take for granted can be eliminated using such algorithms. These visual artifacts include a block pattern at the character joint, a polygon appearance on the car wheel, and a rough facial feature. For example, Stalker: Call of Pripyat uses PN-Triangles to generate more smooth and natural appearance characters.

Seamless fineness

In games with large and open environments, users may notice that objects in the distance often appear and disappear. This is because the game engine is switching between different levels of granularity (SLS) to limit the geometric workload. Because data of multiple versions needs to be stored for the same model or environment, there is no simple method to change the fineness continuously until that time. Dynamic Tessellation solves this problem by instantly changing the fineness. For example, when a building in the distance is first caught in sight, it may only be rendered using 10 triangles. As the user's field of view draws closer, significant features of the building begin to emerge, and more triangles are used to depict details such as windows and roofs. When you finally arrive at the door, one thousand triangles are used for rendering for the old copper door handle alone; Displacement Mapping (texture replacement) carefully carved out each groove. The game environment can now be expanded to almost infinite geometric fineness because it eliminates the time invisibility of dynamic Tessellation (Curved Surface Subdivision) objects.

Easy-to-use art

For developers, Tessellation greatly improves the efficiency of their content creation pipeline. "We are very interested in being able to edit the game content," says Jason Mitchell of Valve, describing his motivation for using Tessellation (Surface Subdivision, this allows us to achieve scaling. That is to say, we want to create a model only once, and then we can upgrade it to the movie quality... On the contrary, we want to naturally reduce the quality of game content to meet the needs of real-time rendering on specific systems ." This capability, which can be used on various platforms only once, means that development time is shortened. For PC gamers, this means that they can achieve the highest image quality on their GPUs.

GeForce®How GTX 400 GPU (graphics processor) handles Tessellation (Surface Subdivision)

The traditional GPU (graphics processor) design uses a single geometric engine to execute Tessellation (Surface Subdivision) tasks. This approach is similar to the early GPU design, which uses a single pixel pipeline for Pixel coloring. After realizing how the pixel assembly line evolved from a single unit into multiple parallel units and how this progress shines in 3D fidelity, from the very beginning, we designed our parallel Tessellation architecture.

GeForce®GTX 400 GPU (graphics processor) has a maximum of 15 Tessellation (Surface Subdivision) units, each of which has dedicated hardware for vertex pickup, Tessellation (Surface Subdivision), and coordinate transformation. They use four parallel grating engines for computation, which can convert triangles subdivided from a new surface into fine pixel streams for coloring. In this way, the performance of Tessellation (Surface Subdivision) has achieved a huge breakthrough, and the durability can reach more than 1.6 billion triangles per second. Compared with the fastest similar products, GeForce®The maximum speed of GTX 480 is 7.8 times. This data is measured by the independent website Bjorn3D.

Conclusion

After years of repeated experiments, Tessellation (Surface Subdivision) was finally successful on the PC. Excellent games such as Metro 2033 have demonstrated the potential of Tessellation. In the end, Tessellation (Surface Subdivision) will become as critical and essential technology as pixel coloring. Due to the awareness of the importance of Tessellation (Surface Subdivision), NVIDIA®From the very beginning, the company built a parallel Tessellation (Surface Subdivision) architecture to promote this process. The result is GeForce.®GTX 400 series GPU (graphics processor)-a real breakthrough in geometric fidelity and Tessellation performance.

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