DirectX 11 Feature: Tessellation

DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator

The first DirectX 11 graphics cards of the HD 5800 series have been released but appropriate DirectX 11 software is still hard to find. One of the most important DirectX 11 features is Tessellation and PC Games Hardware shows what this is all about.
AMD Soldier DirectX 11 Tessellation 12
AMD Soldier DirectX 11 Tessellation 12 [Source: view picture gallery]
DirectX 11 has turned into reality due to the Radeon HD 5800 series and one of the most important features is the Tessellator. But what's this hardware component doing?

With the DirectX 11 Tessellation GPU accelerated polygons are divided so that the developers can use more detailed models. Tessellation splits already existing triangles - almost every 3D model is made of triangles - up into smaller and finer pieces. An example is a barrel viewed from the top: A barrel is often made of a one-digit number of polygons and therefore it looks rather angled. If a game developer writes an appropriate shader program the DirectX 11 Tessellation makes the barrel almost look round as the graphics chip now adds triangles to the former basic object.

What seems to be easy with a simple barrel becomes a challenge with complex scenarios: Despite a high hardware capacity Tessellation requires a considerable amount of computing power. Therefore Tessellation is only used if it makes sense for the player: At silhouette edges and the close environment of the player's view.

The following examples illustrate the effect of a cleverly used Tessellation with DirectX 11. By clicking you can select the different Tessellation settings and the view of the wire frame models.

By the way: Only fully DirectX 11-compatible graphics cards have access to the Tessellation hardware - older DirectX 10/10.1 hardware are left out.

Click to select DX11 Tessellation

In Aliens vs. Predator 2, a DirectX11 shooter planned for 2010, the presentation of the aliens (see picture) as well as other characters and parts of the organic environment should be designed by Tessellation.

Colin McRae Dirt 2 which will be released in December uses the DirectX 11 Tessellation for the design of banners and flags. Furthermore water surfaces should be animated more realistic by using Tessellation if players drive through them.

In a demo of Microsoft's DirectX 11 SDK the face and body of this soldier becomes more detailed via Tessellation. But the armament remains untouched.

The Unigine offers DirectX 11 support and therefore Tessellation as well. The presentation of this house considerably benefits from the increased number of triangles combined with Displacement Mapping.
Click to select Stalker version

In Stalker: Call of Pripyat - the DirectX 11 shooter will be released on November 4 and will be the second available DX11 game after Battleforge - Tessellation is used for more detailed characters.

All comparison pictures can also be found in our gallery. In case you are interested in the DirectX 11 graphics card HD 5870 please refer to our hardware test.

Picture gallery  (enlarge to view source)

Author: Carsten Spille (Sep 29, 2009)

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