Quote:

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Now compare all other coefficients against these extremes and assign a percentage to it.

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I have NO idea what you are talking about agreen.....

I'm not a physics professor, but let me take a stab at it. I *think* (and I use that term loosly) what he wants is for you to take the table Yulor posted, and based on the real life CoF values for ice/ice and rubber/rubber, calculate the proper percentages for the table, instead of the real CoF values it has.

Since I'm not a physics professor, and since I dont know the CoF values for ice/ice or rubber/rubber, nor do i know if any of the values would even have a linear approximation over a % scale, I can't do this. Not that I even care what they are, or if they can be converted.

I *think* the only true way would be to use them to make a SWAG (Is steel on concreted more like rubber on rubber, or more like ice on ice?) and then adjust it based on how the engine reacts, which is what Fastlane alluded to in an earlier post.

Problem is that friction (and the physics around it) are not something that can be broken down into a percentage easily...at least not in anything that translates directly from real world fact to Physics Engine practice.

Fudging the numbers is what you need to do to get the results that you want...forget what the value is on paper or what the numbers say...but ask your self "Does it look right?"

This is important because stuff like rubber on concrete has a very high ammount of friction. Especially when the rubber is a bit sticky...but coefficients only hold true in a perfectly controlled lab environment. However when that rubber gets heated up too much, it becomes very slick (real world example...locking up the tires till they are sliding...melts the rubber and you are hydroplaning on a puddle of molten rubber...leaving balck marks all the way). Ice on ice will actually lock up in most cases... However for a moment it will slide quite well.

Whats the point? There is just too much going on that can not be taken into account in simpified physics simulations to use real numbers. You have to make stuff up as you go in order to achieve realistic results without needing a super computer to process the calculations.

)Thanks Qwerty I think that was it.
Here, I'll spell one way to use this table for those of you that didn't get it:

Been learning UML2.0, so I'll break it down thusly:


1) Analysis: Make a list of all the surfaces that you wish to model in your game.

For example, suppose you want to do a Resident Evil game. Thus it's first person and you'll want to model sneakers on wet and dry pavement. Let's throw in an Artic level and thus have Ice and Snow. Here is my list or Required Surfaces:

Rubber on Dry Concrete
Rubber on Wet Concrete
Rubber on Ice
Wood on Snow (Wood SnowShoes)

Further in the Analysis, I decide that I will use the values for Static Friction. You only use Kinetic Friction if your object is SLIDING, which we are not allowing in our game ATM. All you do is walk and thus use Static Friction.



2) Design: Modify and Rank your surfaces according to available Data

We have straight up values for Rubber/Dry Concrete(1.0) and Rubber/Wet Concrete (0.3).
We don't have rubber/ice, but we can model it as being slightly higher than metal/ice (0.022) but lower than rubber/wet concrete (.3). Thus we safely assign (ie fudge) rubber/ice a value of 0.05.
Finally, I have a straight up value for wood on snow in my book as .14. Here is our rank:

Code:

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Rubber/Dry     1.0
Rubber/Wet     0.3
Wood/Snow      0.14
Rubber/Ice     0.05
 

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3) Implement: Now based on your particular Implementaiton (3DGS), make it happen!

We know that the highest that the 3DGS PE engine does is 100% for rubber/rubber. I don't have rubber/rubber, but I have rubber/concrete. Hey, close enough! So I now assign 100% to be the highest value in my set of surfaces. Now we scale our percentages (and yes, it's divine providence that the numbers turned out so easy....didn't plan it this way.... : )
Code:

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Surface          "Real"       3DGS


Rubber/Dry        1.0          100%
Rubber/Wet        0.3          30%
Wood/Snow         0.14         14%
Rubber/Ice        0.05         5%

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Point is you these aren't hard and fast rules. If I were to add an indoor track level, that would have that rubbery material on the tracks, I would have to adjust my scales accordingly for rubber/rubber.
Likewise if I dropped Dry concrete from my game, now Wet concrete and 0.3 is 100% and your scale is readjusted.

AND ALL OF THIS MAY BE FOR NOUGHT CAUSE IT STILL WON'T LOOK RIGHT IN THE END. YOU ARE STILL GONNA HAVE TO TWEAK THE NUMBERS TO MAKE IT "FEEL" RIGHT!!!!!

I think this should finally clear up any questions, yes/no?