Ouch. I have no idea. I can't think of any level where they were used.
Hmmm... Let me dig around a bit.

I thought that they were how far from the original rotation they could go, like in Hang Low you can't really move the platforms that much...but the values there are both 0 as well! I have really no idea now.

EDIT: Another cross-post with MOM4Evr! Are we always online at the same time?

ONE of the hinges in GeneticSortingMachine had values for highstop and lowstop as well... But these were both 0 also. I dunno. DaB?

I know!
I just haven't had a chance to fully investigate and write them up....

The names actually mean high-stop and low-stop
On hinges they are angles, but in radians.
Hinges begin life / the level at angle 0
High-stop specifies the largest angle (clockwise I think) it's allowed to go to (max PI)
Low-stop (will be negative) the angle anti_clockwise it's allowed to go to (min -PI)

So 0,0 basically locks it in place.

There are several (at least 3) other attributes which control the springy / spongy / bounciness of these end stops.

About the only one I understand is bounce.. its sort of the restitution factor of the end stop...
0 will make the thing stop "dead", 1 will make it bounce right back.

There are 2 others stopcfm and stoperp... but I've not read up on them yet.

But if you want to...everything you ever wanted to know about the Physics Engine
http://www.ode.org/ode-latest-userguide.pdf

Yay! Now only if we can understand how to use these values correctly...

But if it can't rotate, what's the point? And how come they still rotate in the original levels?

thx, DaB!
(sorry, one-liner)

Wow, everyone's online right now!

Ok, this all makes sense now.
Albino Pokey: Hinges can be used to connect geometries together, as well as just being a hinge.
In the original WOG levels, the hinges still rotate because they have no histop and lostop attributes. The hinges that do have 0 for both, thus locking the hinge in place. This is useful if you just want to attach two geometries together, without letting them rotate in relation to one another.
Cool thing about this histop/lostop stuff is that the hinges act like springs, so you can overrotate them. It looks more realistic, though.

Albino Pokey: in case you're playing around with this stuff, try setting histop to pi/4, which is about .785, (a 45-degree angle) and lostop to -.785. I set bounce to .8, which makes for a nice springy rotating rectangle (I toyed with a copy of Server Farm). Add a RectHead to smash it around with. Pretty bouncy!

What's Goofans Web Chat?

EDIT: never mind...

Hmm, I was just toying with the bounce value. I set the histop and lostop to about pi/4, and no matter what I set bounce to, it seemed to act the same. Of course, I could be wrong, but are you sure this value does anything?

That's what it did for me too! Bounce seemed to always be 0!

As I said, not fuily investigated....
It does look like bounce doesn't have very much / any effect on hinges.

There are other values, which I only discovered the other day, that also affect what happens when it hits the stops.. Maybe the "squashiness" 2DBoy have set as default, overrides the bounce effects.

But I know for sure bounce works (as described)... on "something else"