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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)

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Author: Carsten Spille (Sep 29, 2009)


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Comments (17)

Comments 7 to 17  Read all comments here!
erexAmineebub DirectX 11 Tessellation in Stalker CoP Dirt 2 Unig...
Junior Member
27.12.2009 14:18
Put the magazine down, turn the video off and walk carefully and slowly to the shower which should be cold only. You may already be going blind so dont bump into anything as you go.
yanduan Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Junior Member
24.12.2009 12:06
Actually all of them are so subtle
I'm sure I can't notice it when I am playing those games
Thandrin Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Junior Member
25.10.2009 04:30
Hey.
I'm just curious, i'm still not sure how this is working.
If i'm mapping textures say on the ground with rocks or what not, am i able to turn on tessellation and it will automatically add the geometry for the ground? This seems unlikely i know, but what do you need to do if you want to make your own ground with tessellation?
Do you need the light information from bump maps or something?
Someone clear this up for me please, thanks.
ruyven_macaran Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Super Moderator
01.10.2009 16:41
Zooming in, meanding a new LOD-system, might profit.
But your simple model will not or not very much:
After tesselation created a complex, rounded modell from the simple baselines, the rest of the card still faces a huge mass of triangles for calculation. Tesselation only eased up the transfer of these triangles from cpu to gpu and probably the very basic geometrics. But these aren't limitting at all in the moment, especially if you don't want to use over the top models.
ruyven_macaran Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Super Moderator
30.09.2009 17:58
The first element you describe is normal mapping and works without tesselation - and cannot be based on your everyday bumpmap.
The second element is the very problem: Usually you have a triangle with certain properties - end of discussion.
If you want to use tesselation, you don't want to work with triangles. You want to work with complex curvatures, that graphic cards up to now didn't even now to exist. Forcing the card to consider several triangles, calculate the curve they should represent and then calulate several more triangles, that represent this curve a lot better, is not so easily done with few minutes invested in shader code. At least not, if it should be fast, free of errors and applied to all curvatures in the game. (the later sentence is the part, that modders can skip completely...)
connos Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Senior Member
30.09.2009 16:57
Quote: (Originally Posted by Heiko)
I think when using it as an enhancer for bump mapping it should be quite easy to implement. The bump maps are already there. The only thing to be done is write a shader that adds in the the extra triangles based on the heights in the bump map. Can't be easier tbh. Existing games could even be adapted to use this.

Similar things can be done using just the normals of models. With the normals of a triangle and a bezier function, you can obtain very nice round surfaces. That is how that gas mask looks perfectly round, quite a tough effect to obtain without tesselation (or you'll have to put a massive amount of triangles into the model, which makes it quite expensive to render, even if it is so far away that you wouldn't see the effect because the model is tiny at that distance).

Why would this be hard for modelers? The game engine writers only have to create a couple of standard effects with the tesselators (like making use of bump maps, or creating the round surfaces) and the modelers can just turn these effects on/or on their models using the tools that come with the game engine. Nothing hard about it...


Well said!!
haplo Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Member
30.09.2009 00:20
Quote: (Originally Posted by Unregistered)
...U R A Tool.


FU*K YOU Unregistered.
JDA Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Junior Member
29.09.2009 21:35
How very deceptive. I'd expect nothing less from tech demos, but this is especially confusing for technical laymen.


Quote: (Originally Posted by connos)
Its how it will be used that will be impressive. I find it a nice think to have and we will see how it will go. I think the impressive think of tessellation is that is very easy to implement on your existing models? There is no deference in Stalker model from previous installments + tessellation.


Tessellation is EXTREMELY DIFFICULT TO IMPLEMENT, at least to implement well. Artists are already completely overloaded, which is why so many games have bad art at least in places. Very few studios will be able to cope with the additional work load this tool will provide.
connos Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Senior Member
29.09.2009 14:11
Its how it will be used that will be impressive. I find it a nice think to have and we will see how it will go. I think the impressive think of tessellation is that is very easy to implement on your existing models? There is no deference in Stalker model from previous installments + tessellation.
haplo Re: DirectX 11: Tessellation in Stalker: CoP, Dirt 2, Unigine and Alien vs. Predator
Member
29.09.2009 14:06
haha. lets badmouth DX11 ppl!

the guys are right. Surprisingly enuff, only the roof comparison made me go Wow. Everything else was so lame.

The AMD soldier was a shocker. The wireframe looked crazy but the model itself was so, almost the same.

I guess the oni thing DX11 card owners can brag bout is if they play a game in full wireframe mode. They can tap each other's behind and drool at how dense the wire mesh looks on their rig.

Still waiting to be knocked off my chair by the technology that supposedly made my 4870, at only 512mb mins you, obsolete.

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