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Momentum question

Posted: Fri Nov 11, 2005 1:02 am
by The Purple Panzer
If I get the momentum flag, it is as if I have increased mass when I travel in the x, y directions. Should it not also apply to the vertical? My jumps should have slower acceleration, and then my momentum should carry me upwards a bit.

This might seem like a niggle, but my intuition is bothered by this: I'm in molasses driving around on a map, but when I jump I'm as light and quick as ever. Turning when jumping seems too fast too - my angular momentum should also suffer.

(To take this to an extreme, when coming down one might even burrow a tiny bit, with reduced radar and speed, and then gradually dig out of the hole.)

Posted: Fri Nov 11, 2005 1:24 am
by Hannibal
actually, i think that when you have M the friction on the ground is decreased, allowing you to slide more.


Posted: Fri Nov 11, 2005 1:46 am
by The Purple Panzer
Increased 'momentum' would mean increasing mv, mass times velocity; I would expect that this would be implemented as an effective increase in mass. (Friction should then increase as the normal force caused by gravity would increase. As you point out, in the game it doesn't.)

Now you could sort of fake out increased momentum/mass by decreasing traction, as you'd still 'go more in the direction you were going'; this ignores the increased friction due to greater weight issue.

If you really increased mass, it would take more force to change the momentum, and f=ma really is f=d/dt(mv) anyway. That is if the tank has a fixed amount of propulsive force, it will change momentum at a certain rate; increasing mass will reduce this rate. So maybe the 'momentum' flag could be named the 'increased mass' flag (IM), which is the only sane way to (really) change the momentum in the game.

But my point was that this should apply in the vertical direction as well as the horizontal ones. It might be an easy hack to decrease friction on the surface, but if that's all it does it'd probably be better named something like 'greased treads', or GT.

This is all safely ignored if the effect is good, and I think my main concern is that the effect shows up in 2 out of the 3 dimensions that the tank moves in, which seems non-intuitive at best, non-physical at worst.

Posted: Fri Nov 11, 2005 2:24 am
by Teppic
The wings flag has it's own impulse and gravity setting so there is no reason M shouldn't get that too, to mimic a mass increase anyhow. The M flag sets limits on angular and linear acceleration, I havn't seen a setting for M friction.

Posted: Fri Nov 11, 2005 2:55 am
by Hannibal
ah well, science has defeated me yet again.

but it sure seems like all it is is the friction being changed. *wonders where jeff is on this one...*

Posted: Fri Nov 11, 2005 4:39 pm
by Longhair
Here's the relevant server variables for the momentum flag:

_momentumAngAcc adjusts the amount of inertia for right to left
_momentumFriction creates a "slippery" effect
_momentumLinAcc adjusts the amount of inertia forward and back

AFAIK, there is no adjustment for jumping with the momentum flag, but you can change how much slide the tank has. Normally, _momentumFriction is set to 0, but any value over 0 will add some loss of friction. The closer the number is to 0, the slipperier it will get. ie. 0.8 is more slippery than 2.

Posted: Fri Nov 11, 2005 11:40 pm
by Hannibal
Longhair wrote:_momentumFriction creates a "slippery" effect.
HAH! i was partly right...