Tessellation (surface subdivision) displacement Mapping (map displacement)

DirectX one-tessellation (surface subdivision)-What is tessellation (surface subdivision)?

Why does it have such critical data?

With the recent buzz about DirectX 11, you've probably heard a lot about the most new features of DirectX 11 tessellation (surface subdivision). As a concept. Tessellation (surface subdivision) is very straightforward, that is, processing a polygon into many small fragments.

But why is this way of handling so much attention?

How does it help improve the quality of the game? In this article, we will analyze why tessellation (surface subdivision) can bring profound changes to PC 3D graphics, and explain how the NVIDIA®GEFORCE®GTX 400 series GPU provides breakthrough Tesse Llation (surface subdivision) performance.

Essentially, tessellation (surface subdivision) is a method of decomposing polygons into finer fragments to enhance geometric fidelity.

For example, assuming that a square is processed and cut diagonally, the square "surface subdivision" is actually a two triangle. In itself, tessellation (surface subdivision) does not increase the slightest fidelity.

For example, in the game. Whether a square is rendered as two triangles or 2000 triangles is irrelevant.

Tessellation (curved subdivision) can enhance fidelity only when new triangles are used to describe new information.

When a displacement map (left) is applied to a plane, the resulting surface (right) displays the height information encoded in the displacement map.

The simplest and most popular way to use a new triangle is the technology called Displacement Mapping (map replacement). A map of displacement is a texture that stores height information. When applied to a surface, the map allows the vertices of the surface to be increased or lowered according to the height information. For example, using a marble slab, a graphic artist can create a carving effect by "displacing" vertices. Another popular technique is to apply displacement maps to the terrain to carve out craters, canyons, and peaks.

Just like tessellation (surface subdivision). Displacement Mapping (map substitution) has been around for a very long time. But until recently, it was really popular.

The reason for this is because you want to make displacement Mapping (map replacement) effective. The surface must consist of a large number of vertices. Take the marble carving as an example. Suppose the marble block consists of eight vertices. Then there is no relative displacement between them that can generate a dragon-shaped relief. A careful relief can be generated only when there are enough vertices in the underlying mesh to depict the new shape.

Essentially, displacement Mapping (map replacement) requires tessellation (surface subdivision). Vice versa.

With the advent of DirectX 11. The tessellation (surface subdivision) and the Displacement Mapping (map displacement) finally achieve a perfect match. The vast majority of developers have increased to this camp among them.

Like "Alien vs. Predator" and "Metro 2033" This popular game uses the tessellation (curved subdivision) to generate a smooth appearance of the model, and the developer valve Company and id Software has completed some promising work, Apply these techniques to their existing game characters.

When a rough model (left) is processed by tessellation (surface subdivision), a smooth model (middle) is generated. After the map displacement has been applied (right). The game characters are close to the movie-like realism. ©kenneth Scott, id Software All rights reserved. 2008

Because DirectX one-tessellation (surface subdivision) pipelining is programmable. So it can be used to solve a lot of graphics problems. Let's take a look at four examples.

Perfect Bump Map

Essentially, displacement Mapping (map substitution) can be used as a temporary replacement for existing bump mapping techniques. Current techniques, such as normal mapping, can create an illusion of concave and convex surfaces through better pixel rendering. All of these technologies are only effective in specific situations and are not all that realistic when they are in effect. The following is an example of a more advanced parallax masking map in bump mapping.

Although it can generate overlapping geometric artifacts, it only works on the plane and inside the object (see). True displacement Mapping (map permutation) does not have these problems and can produce accurate results from all perspectives.

More smooth characters

Without the artist's manual input, pn-triangles can realize the self-active smoothing of the game characters. Both geometry and illumination fidelity can be improved.

The refinement algorithm is tessellation (surface subdivision) and a natural partner. The refinement algorithm can handle rough models with the help of tessellation (surface subdivision). The algorithm creates a more smooth-looking model. Pn-triangles (also known as N-patches) is a popular example. The Pn-triangles algorithm transforms a low-resolution model into a curved surface that can then be drawn again into a mesh of triangles that are subdivided by high-precision surfaces. In today's game, we take for granted that a large number of visual artifacts can be eliminated with this kind of algorithm. These visual artifacts include a blocky pattern in the character's joints, a polygonal appearance on the car's wheels, and a rough facial feature. For example, "Stalker:call of Pripyat" uses pn-triangles to create a smoother, more natural figure.

Seamless fine-grained

In the game with a large, open environment. Users may notice that objects in the distance often appear at times, sometimes disappear. This is because the game engine is switching between different degrees of refinement (LOD) to limit the geometry workload. Because you need to save multiple version numbers of data for the same model or environment. So until that time, there was no simple way to change the fineness continuously.

Dynamic tessellation (surface subdivision) changes the fineness in real time. Overcame the problem. Like what. When a distant building is first greeted, it may be rendered using only 10 triangles. As the user's horizons narrowed, the building's salient features began to emerge, and many other triangles were used to depict details such as windows and roofs. When you finally arrive at the door, the old brass Door knob alone uses 1000 triangles for rendering; displacement Mapping (map replacement) carefully carved out every groove.

Because of the elimination of the dynamic tessellation (surface subdivision) object's disappearing. As a result, the game environment can now be extended to almost infinite geometrical granularity.

The Art of Retractable freedom

For developers, tessellation (curved subdivision) greatly improves the efficiency of its content authoring pipeline.

When describing a motive for describing its use of tessellation (curved subdivision). "We are very interested in the ability to edit the content of the game so that we can zoom in," says Jason Mitchell of Valve.

Other words. We want to just make a model once and then we can lift it to the movie quality ... Instead. We want to be able to naturally reduce the quality of the game content to meet the need for real-time rendering on a particular system.

"This ability to create a model for use on a variety of platforms means that development time is shortened. For PC gamers, this means the highest image quality can be achieved on their GPU.

Geforce®gtx how the GPU (graphics processor) handles tessellation (surface subdivision)

The traditional GPU (graphics processor) design uses a single geometry engine to run tessellation (surface subdivision) tasks. This scenario is similar to the earlier GPU design, which uses a single pixel pipeline to run pixel coloring.

After recognizing how pixel pipelining evolved from one unit to multiple parallel units and how this progress was made in 3D fidelity, we designed our own parallel tessellation (surface subdivision) architecture from the beginning.

The GEFORCE®GTX-x GPU (graphics processor) has up to 15 tessellation (surface subdivision) units, each with dedicated hardware for vertex pickup, tessellation (surface subdivision), and coordinate transformations.

They use 4 parallel raster engines to perform operations that convert the triangles of a recent surface subdivision into fine pixel streams for coloring. As a result, the performance of the tessellation (surface subdivision) is a huge breakthrough. Durable performance up to 1,600,000,003 corners per second. The GEFORCE®GTX 480 is up to 7.8 times times faster than the fastest comparable product.

This data was measured by the independent site Bjorn3d.

Conclusion

After years of repeated experimentation, tessellation (surface subdivision) eventually succeeded on the PC.

"Metro 2033" and other excellent games have shown the potential of tessellation (curved subdivision). Finally, tessellation (surface subdivision) becomes as critical and indispensable as pixel coloring.

Aware of the importance of tessellation (surface subdivision). NVIDIA® Company has created a parallel tessellation (surface subdivision) architecture from the outset to drive this process.

The result is a real breakthrough in the GEFORCE®GTX 400 series GPU (graphics processor)-Geometric fidelity and tessellation (surface subdivision) performance.

Tessellation (surface subdivision) displacement Mapping (map displacement)