Tessellation

[jdude]

I've never heard of this but I find Tessellation to be a very impressive advancement in graphical technology. I find discovered it when I saw this:

http://www.pcgameshardware.com/aid,695861/...reenshots/News/

It made no sense to me so I looked around and found this video which explains the concept quite nicely:

 

So this will be packaged in Direct X 11. I think I will be upgrading to windows 7 when the time comes

[SplaTtzZ]

Wow the screens and that video seem pretty impressive.

 

I know very little about graphics and modelling; but i'm assuming Tesselation allows you to produce better looking curves in a model without increasing polygon count?

By which i mean instead of adding more and more vertices to try and create a curved or circular object you can simply create a rough outline and use tesselation to simulate the curve?

[Domarius]

Tessellation means creating more polys

 

The advantage here I guess is it's all being done on the GPU, so maybe it's faster, or adaptive, or something.

[Crispy]

Yeah, looks like speed and flexibility are it. As far as I can tell, it sounds like you can feed descriptions of curved surfaces (patches) straight into the GPU and it will turn them into polygons at runtime depending on how close you are to them. Fully automatic and freely scalable LOD, in other words. Good overview here: http://www.bit-tech.net/bits/2008/09/17/di...what-s-coming/3

[jdude]

I'm a little confused about the polygons as well... Do you think it will be employed for objects only in a particular distance from the player?

[Tels]

Yeah, looks like speed and flexibility are it. As far as I can tell, it sounds like you can feed descriptions of curved surfaces (patches) straight into the GPU and it will turn them into polygons at runtime depending on how close you are to them. Fully automatic and freely scalable LOD, in other words. Good overview here: http://www.bit-tech.net/bits/2008/09/17/di...what-s-coming/3

 

Yeah, and we had that for a couple of years (probably even 10) now, but it didn't take of (maybe because each manufacturer of graphic cards did it their own way...)

 

Here is a discussion from 2002 about the matter, back then it was called "Trueform". Today it will probably be called "MegaTrueSuperDuperModelEnhancer 2.0"...

[Crispy]

I'm a little confused about the polygons as well... Do you think it will be employed for objects only in a particular distance from the player?

No, it'll be in use all the time (for objects that use it). Basically instead of modelling directly in polygons, modellers will use some kind of fancier system like subdivision surfaces or NURBS surfaces (actually most professional modellers do this already, at least for organic objects). Models in such formats can be converted into polygonal models with arbitrary polygon counts. The models get sent to the GPU in their original fancy format, and then the GPU converts them into polygon models dynamically, at runtime, with the detail level depending on how far they are from the camera. So really distant objects will be displayed with only a few polygons (thus speeding up rendering when the extra polygons aren't visible anyway), and really close ones will get extra detail (so objects don't look obviously low-poly when you get up close). Fully automated level-of-detail.

 

(Level of detail is where you use low-poly models for far-away objects, but use high-poly models for close objects. Without tessellation, you have to manually create your low-poly and high-poly models separately. Tessellation lets you have one model, which gets converted into lots of lower-poly and higher-poly variations at runtime.)

 

I think you left out your link, Tels.

[Domarius]

I'm a little confused about the polygons as well... Do you think it will be employed for objects only in a particular distance from the player?

Well a curve is stored as a few numbers - the start, and end, and some parameters that describes how it bends. With those numbers you can find any point along the curve. So you can make 3 points along the curve, connect the dots, and get a very sharp crooked line, or make 100 points, and get a much smoother line. Tesselating a curve into polygons works like that - you just decide how many polys you want for one curve, then create them.

 

Naturally all this real-time tesselation won't be free, so I'd say they'd only make certain objects use this feature - I'd say human faces, domes on buildings, etc. Things that you'd care to see looking very round up close. Architecture with straight edges, scenery that you never get close to - those things would just be normal polys.

[Tels]

I think you left out your link, Tels.

 

Sorry, forum gnoll ate it:

 

 

http://www.sysopt.com/forum/showthread.php?t=86477

 

(not the one I had but couldn't find it again

[AluminumHaste]

That's been around for a long time, ATI came up with a Hardware implementation back in the day called Truform that was done on the Radeon 8500. Check out the video here: http://media.amddevcentral.com/video/gpu_Videos/ATI-8500-Dolphin-Demo-v1.0.avi

 

Unfortunately there is only software support for this now as the HW that was built into the 8500 was dropped in later GPUs. Nvidia has the same thing called N-Patches. Morrowind supported this, on both ATI and Nvida hardware. Looks good too, but had a large performance hit.

[jdude]

It seems like it's been a matter of the technology catching up with the software then.

[STiFU]

Nice guesses so far... ;-) I've tested the new ATI dx11 card at work under windows 7 and checked out the dx11 demos of course. You woun't get any details from me, but I can tell you this: The tesselation demos use textures (heightmaps I assume) instead of splines, so it's best comparable to "sub-poly displacement mapping". You have a fairly good qualityincrease with a tesselationfactor of 3, but it also reduced fps by one half. The Qualityincrease at higher factors is hardly noticeable.

 

But the in my oppinion much more interesting feature of DirectX 11 is that you can perform all kinds of calculations on the gpus now with any DirectX 10 capable graphics adapter, in a similar fashion to nVidia's Cuda & PhysX. I'm really anxious to see the forthcoming developments in this area.