Environment Size Limit?

XN-Sigma · Nov 8, 2012

I'm not sure if Aris can/is allowed to answer this but I'll ask anyway.

Is there an environment size limit hardcoded in the engine? Some days ago I was at the WMD forums reading some threads and someone said that pCARS has an environment limitation of 16x16km, so tracks can't be any bigger than that, and so I was wondering about AC and if it has such a limitation, if yes, what would be the size?

And then someone may say "Why would a track need to be so big?", well why not?

magicfr · Nov 9, 2012

If the world is not streamed and "shifted", and also if AC engine uses float to describe vertices position, then there is a limitation on the floating point dimension to describe real numbers.

If you use to large number , like 16km ( 16000 meters ), you start too loose precision in the decimals.
For example, with 16000 meters you can have let say 3 figures after in the decimal parts, so something like 16000.569. So it's precis to the millimeter.
But with 160km, you loose 1 figure, 160000.56. So now you only precise to centimer. Wich can lead to graphical glitches. And worst, physics innacuracy.

For Test Drive Unlimited we stream the world, and we shift it. So everytime the cars is moving of 6km, we shift the whole word, so all objects position have value lower than 6000meters. So the only limit were the size of the DVD

Back to the question. If AC don't have such shift feature, and they use float to store real numbers it will be limited to something around 16km too.

If AC engine use double to store positions, then it will be limited too, but with really bigger size, Something around 16 million kilometers.

Now you may think using double will make the game slower, well, not on 64bit OS.

In our current project I can switch my physics engine from float to double, and I see no difference on performance on Win7 64bit.

XN-Sigma · Nov 9, 2012

Interesting explanation, and actually, a few months ago I tried making large maps in CryEngine 3 to see how it would work, and it had that exact problem, at around 16km away from the starting point the engine started having problems like doing a lot of flickering on the horizon and generally messing up the graphics, trying to move the camera too much beyond 16km actually made the engine crash. I do know the Unreal Engine 3 has a hardcoded 10x10km limit, the UDK doesn't even let you go beyond that size.

And that idea of moving the map instead of the car is simply genious.

Would be cool if AC could do that.

magicfr · Nov 9, 2012

Well, that's the only smart idea that came in my mind to resolve the problem at that time

I was using Havok for collision detection I couldn't change it to use double.
Also the X360 was not liking double for real numbers

Hampus Andersson · Nov 9, 2012

Arma has some seriously big maps. I think Limnos will be the biggest one.

magicfr · Nov 9, 2012

Test Drive Unlimited was made with O'ahu 1:1 scale

magicfr · Nov 9, 2012

Here a nice comparison :

Hampus Andersson · Nov 9, 2012

Now that i think about it. I think EVE Online might just trump every other game out there.

XN-Sigma · Nov 9, 2012

Hampus Andersson said:
Now that i think about it. I think EVE Online might just trump every other game out there.

hmm... EVE is an space game right? So there really isn't an actually modeled map, just a BIG inside-out sphere with a texture on it for the stars and then the rest of the stuff (planets, ships, asteroids, etc) is probably done like magicfr said, though I've never played it so I dunno really.

Hampus Andersson · Nov 9, 2012

XN-Sigma said:
hmm... EVE is an space game right? So there really isn't an actually modeled map, just a BIG inside-out sphere with a texture on it for the stars and then the rest of the stuff (planets, ships, asteroids, etc) is probably done like magicfr said, though I've never played it so I dunno really.

Yea it´s the space game.
Yea i have no idea really i just thought that since that game is "more 3D" if that makes any sense.

Not just forward, backwards, left and right but up and down as well.

magicfr · Nov 9, 2012

Well, Space game, make a huge world ... full... of... empty space is not a challenge

Kjell Eilertsen · Nov 10, 2012

magicfr said:
Here a nice comparison :

Thanks for that map!

ufunacaoenn · Nov 11, 2012

An important thing to take to account though is that if you have to much space to work on (adding trees and other stuff) it will cause people with low performance PC to have a bit of a problem if the graphics engine requires a lot of CPU.

Lee Knight · Nov 11, 2012

I like long tracks & am currently working on several for rF in BTB (which Ive been considering converting to AC in time).
My largest one is an 84km loop in a roughly triangular layout & to keep the inherent problems Gmotor2 has with large tracks I try to set them with location 0.0.0 as central to the layout as possible....
Would tracks of this size cause troubles for AC?

XN-Sigma · Nov 12, 2012

I'm not sure how an 84km loop would work in AC, if AC has the same kind of limitation as pCARS then probably wouldn't work. But maybe Kunos thought about this kind of stuff and made the engine support bigger environments, what makes me think this is that some of the devs, Aris probably, said there is no hardcoded limitation for the amount of cars on track, the only limitation would be the user's hardwere and discretion. So there's that.

diesirae · Nov 18, 2012

As magicfr said, it depends on what kind of tech they use, but my guess is they haven't implemented streaming to support very large tracks properly (without streaming you're likely to run into some heavy performance issues as well) and uses floats like pCARS so I'd say it's likely that 84km is out of the question, but only the devs can provide an answer at this point.