About Directx11

Source:http://uk.geforce.com/hardware/technology/dx11/technology

The most powerful and popular feature of DirectX11 is TESSELLATION which leads to the following advantages:

Perfect Bump Mapping

At its most basic, displacement mapping can be used as a drop-in replacement for existing bump mapping techniques. Current techniques such as normal mapping create the illusion of bumpy surfaces through better pixel shading. All these techniques work only in particular cases, and are only partially convincing when they do work.
		Base Model	Bump Mapping	Displacement Mapping
Take the case of parallax occlusion mapping, a very advanced form of bump mapping. Though it produces the illusion of overlapping geometry, it only works on flat surfaces and only in the interior of the object. True displacement mapping has none of these problems and produces accurate results from all viewing angles.

Smoother Characters

The other natural partner to tessellation is refinement algorithms. A refinement algorithm takes a coarse model, and with the help of tessellation, creates a smoother looking model. A popular example is PN-Triangles (also known as N-patches). The PN-Triangles algorithm converts low resolution models into curved surfaces which are then redrawn as a mesh of finely tessellated triangles. Much of the visual artifacts that we take for granted in today’s games—blocky character joints, polygonal looking car wheels, and coarse facial features, can be eliminated with the help of such algorithms. For example, PN-Triangles is used in Stalker: Call of Pripyat to produce smoother, more organic looking characters.

PN-Triangles enable automatic smoothing of characters without artist input. Both geometry and lighting realism is improved.

Seamless Level of Detail

In games with large, open environments you have probably noticed distant objects often pop in and out of existence. This is due to the game engine switching between different levels of detail, or LOD, to keep the geometric workload in check. Up until this point, there has been no easy way to vary the level of detail continuously since it would require keeping many versions of the same model or environment. Dynamic tessellation solves this problem by varying the level of detail on the fly. For example, when a distant building first comes into view, it may be rendered with only ten triangles. As you move closer, its prominent features emerge and extra triangles are used to outline details such as its window and roof. When you finally reach the door, a thousand triangles are devoted to rendering the antique brass handle alone, where each groove is carved out meticulously with displacement mapping. With dynamic tessellation object popping is eliminated, and game environments can scale to near limitless geometric detail.

Scalable Artwork

For developers, tessellation greatly improves the efficiency of their content creation pipeline. In describing their motivation for using tessellation, Jason Mitchell of Valve says: “We are interested in the ability to author assets which allow us to scale both up and down. That is, we want to build a model once and be able to scale it up to film quality…Conversely, we want to be able to naturally scale the quality of an asset down to meet the needs of real-time rendering on a given system.” This ability to create a model once and use it across various platforms means shorter development times, and for the PC gamer, the highest possible image quality on their GPU.

After many years of trial and error, tessellation has finally come to fruition on the PC. Stunning games like Metro 2033 already show the potential of tessellation. In time, tessellation will become as crucial and indispensible as pixel shading. Realizing its importance, NVIDIA has jump started the process by building a parallel tessellation architecture from the get go. The result is the GeForce GTX 400 family of GPUs—a true breakthrough in geometric realism and tessellation performance.  

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