More news on Instancing

[Bigjakkstaffa]

Quoted from www.driverheaven.net


Yesterday we published details on FarCry 1.2, part of that editorial focused on the ability to enable Instancing on the Radeon X800 within FarCry. Since publishing the details we have been working with www.tommti-systems.de to get their Nvidia Instancing demo working on the X800. With very little trouble (only a change to the program which removed a SM3.0 check) Tommti provided a fixed exe and the demo was up and running.

To recap for those of you who dont know or have forgotten what Instancing is... Instancing is a technique where large numbers of identical objects can be grouped together and processed as a batch, greatly reducing the work required by your system. Example real gameplay uses are trees and grass in FarCry and in the Tommti Demo Asteroids or Ships. With traditional rendering each object has to be processed seperately.

The demo works in a very simple but effective way, a scene is rendered where the same object (asteroids or ships) is displayed a large number of times. The number of objects is user definable however asteroids is set to 16,000 by default and ships to 1. With regards to running the demo there are 2 modes which can be chosen, Instancing on and Instancing off. The program monitors peformance and reports the current FPS to the user. It is also possible to move the camera throughout the scene if you require to do so.

With the patch up and running (Using the same 8.041 ATI drivers used for the Farcry patch) we monitored performance.

For reference Tommti's 6800GT clocked at Ultra Speeds achieved up to 3fps with instancing turned off and up to 40fps with instancing enabled (Shader Model 3 support).

Our X800XTPE achieved 4.5fps with instancing off and 48fps with instancing enabled (SM2.0b).

Nvidia have been more than enthusiastic about the benefits of Instancing support in their NV40, we can see they were absolutely correct to feel this way. Implemented correctly its a great feature and not only does the Radeon X800 support it and the performance benefit is equally large, other DX9 class ATI cards also support this feature.

Lets hope more developers follow Crytek's lead and implement this feature for the NV40 and all DX9 class Radeons asap.

Amen to that!

--Jakk:t

[Vampiel]

Wow, what demo was this? That Tommi made? Just some demo, not a game?

That's a pretty big gain.

[Bigjakkstaffa]

I think it was an Nvidia tech demo (so as with all tech demo's - wildly optimisitc then :)), sadly real world implementation isnt so promising. I've seen the benchmark figures for Far Cry (X-Bit and Firingsquad have been playing with the new rendering optins and the like recently) with instancing enabled and the gains around around 5FPS on average (not huge, but nothing to be laughed at).

Considering initially Instancing looked to have no performance benefits at all, this is pretty good news, particulalry for those of us on older cards who'll take all the free FPS' we can get :)

--Jakk:t

[Vampiel]

5 here, 5 there, it add's up. Well I must say that im glad that ATI is working to beef up sm2.0, make's thing's better for me, and maybe I will skip this generation of card's before my next upgrade if these kind's of thing's keep popping up.

[Bigjakkstaffa]

It'll be interesting to see how SM2.0 is developed for the R3xx, as technically the SM2.0b features which gave the X800 such a boost in Far Cry arent supported by the R3xx, because SM2.0b has a larger shader instruction length limit than SM2.0 - and hence that found on the R3xx.

However, any SM2.0b operations which fit within the 96 (i think) instructions specification of the R3xx cards can be executed. SImilarly any SM2.0b instructiosn which are longer than the 96 limit can also be carried oout on the R3xx but multiple passes will be necessary.

As such it sounds uncertain to me as to wether developers will give the R3xx SM2.0b features as they will the X800. That said, its not massively difficult for a third party (such as Demirug with Far Cry) to recompile the shaders for usage on the R3xx.

--Jakk:t