Havok upgrade: Cannot support Havok FX and GPU physics acceleration?

Yes, we shall skip all the Havok jokes.

When the upgrade finally arrives, I see a potential problem for LL with how Havok has been positioning its latest physics engine advancements in the gaming market.

As you may know there is a PCI-based physics accelerator known as PhysX. This product is a competitor to Havok, and as such there will likely never be support for it in Havok.

Instead Havok claims that there is now plenty of spare GPU power to do physics just simply using the graphics accelerator that every serious gamer already has in their home computer. There's no need for another separate physics accelerator.

While good for the home gamer, it may be a problem for LL and its future use of Havok. Remember, LL is running the grid on datacenter servers. With the huge amount of hardware in use these are no doubt pizzabox 1U servers to pack them into a small space. 800+ grid servers even at 1U is equivelant to 20 standard racks 40U high not including anything else like networking, battery backup, etc.

Since Havok FX uses a GPU for physics acceleration, if LL is going to ever use Havok FX then its servers are going to need a video card installed with a GPU. And just how many 1U pizzabox servers have 16x PCI-Express slots? Um, almost none. You don't see 16x PCI-Express in servers usually because system builders say to themselves "Why would anyone system administrator need that?"

I'm having a very hard time finding any 1U server with 16x PCI-Express. Not that you could fit one in anyway since the GPU would have to lay sideways and most fan systems would have no clearance to suck air in across the GPU heatsink.

Even for full-size 5U datacenter servers, they typically only go up to 8x PCI-Express, and many often use a 16x slot but only with 8x capacity. So far I have not been able to find anything that says if a 16x card can function at all if plugged into an 8x slot.


And so unfortunately LL may have big problems if they do eventually plan to move to Havok 4 and use Havok FX physics acceleration. So far it looks like a datacenter-grade Xeon server just would not be able to handle a real 16x PCI-Express GPU.

-Javik

The GPU surely though is only required if EXTRA processing power is needed? Unless LL immediately starts ramping up the complexity of the physics engine after the upgrade, then there is no reason they should need it. If they keep the system as is, then upgrading to Havok X should allow the existing stuff to run faster and more accurately.

Besides that, a 16x PCI-Express slot isn't needed either. Since the SL servers currently don't use ANY GPU power, then even a basic graphics card would give them a fair amount of processing power if needed. Gamers running a physics heavy game may have some GPU wiggle-room if the game is only utilising 75% of their card for its graphics, but the SL servers don't do ANY graphics related stuff so 25% of a high-end card could happily equate to 100% of a cheapo AGP card

doesn't see this as a problem, it might have only a use for the client machine for calculating local stuffs like ragdoll physics and various non critical stuffs, bu all in all no game ever required the server compodent to have a graphic card.

Havok 2 or 3.... not FX, wrong version, bub.

Havok FX is for rendering special effects... that's something you "could" use in SL viewer....

A little research couldn't hurt.

As far as games are concerned, most physics are used for special effects, such as shrapnel from breaking a wooden box. The reason it is an effect is because some people are not going to have a GPU or whatever to support that ability, and so for these people the physics are unceremoniously ripped out and just not shown or used at all.

So most PC games do not try to be too dependent on complex physics and use it for nonessential effects since you have to be able to dumb it down for people playing on 3 year old hardware.

Second Life doesn't work that way. Physics is the core of everything. Even a simple dance club with people just standing around will heavily use physics, because that is how the sim keeps you from being able to walk through the middle of someone in front of you.

This 40-user sim limit is probably very much related to the physics processing capability of the sim. Too many people in the same sim overloads the physics engine and drags everything to a crawl.


So, it is my impression that having sim support for physics acceleration may go a long way towards increasing the number of people a sim can support.

If you can completely offload physics onto a GPU, so much the better! That means more time available for LSL script processing.

This is not a trivial issue. It's very important to the future scaling up of sim populations in Second Life.

.

Maybe a very different model where the server offloads the physical scan calculations to one of the clients using some of this available gpu puwer to advise the server and any other subsequently connected clients of collisions as they are about to occur. That would be a big change. Problems would arise if the client's gpu had minimal capability left over.

Another possibility might be a DSP card to provide the horse power for the physics calculations. These cards might be easier to fit to a bladed thin server PC than a graphics card.

Yet another solution might be to design a dedicated high speed stand alone micro to manage a sim's physics interactions and connect it to the sim thru the network. When the sim count goes over 10,000 or so that might become economically feasible. With mono each server might be able to run far more than just 4 sims and the users would experience less lag.

Havok?!?!?
Which 1 2 3 4 5
Well can link it to the existing two 8800 series to complete the setup...going to be nice to link three GC togther!

I'd be surprised if that's the case and it's not either communications or data access limiting the users - avatars are physically simulated using a stretched sphere and are processed like an un-physical prim when sitting down.

Anyway, on topic: the Havok FX acceleration cannot write back to the general physics system so, as Vincent said, is limited to effects. Essentially it's like SL's particle system - a physics engine for non-physical objects. So there's no way to use it on the servers... unless you want a really fancy status display.

It could however be used to allow people to tone down physics useage. For example, if I have something using physics to achieve a particular effect, but which doesn't really need to collide with things, then that could be made into a client-side physics effect instead.
Although I do suspect the vast majority of physics effects require some server-side collision handling, this would mainly be an extra feature for people who want explosion debris or some such.