Ground Friction and Resistance Index

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Re: Ground Friction and Resistance Index

Postby Senter | 326 » Wed Jun 17, 2015 1:28 am

I am new to track making, so how do I put these different resistances on my track?

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Re: Ground Friction and Resistance Index

Postby SMR 510RR » Sun Jun 21, 2015 4:35 am

You put them in the tileinfo file. Check out the tileinfo info thread, it goes into more detail about the settings and how to set it up. You can always check out another track too to see how it is setup.

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Re: Ground Friction and Resistance Index

Postby Jay » Tue Jul 07, 2015 1:30 am

https://docs.google.com/spreadsheets/d/ ... 1006400369

I made this when I made SXON I think I have already released it however thought I might re link it ... feel free to download it and play around
Image

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Re: Ground Friction and Resistance Index

Postby Motocrosser_44 » Sat Jan 02, 2016 6:11 am

does anyone have a tileinfo file that feels like soft dirt? not mud but softer dirt than your normal dirt. if so, thank you. and I'm new to track making so. please help a rookie out
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Re: Ground Friction and Resistance Index

Postby ColtonD719 » Thu Jul 21, 2016 6:29 pm

What are the default settings for grass/dirt on the blank track, before editing tileinfo?

I've tried

Code: Select all

friction 1.0 1.0
roll_resist 25 50 0

as someone suggested but that didn't feel right at higher speeds.

Right now I just have

Code: Select all

texture @dirt.ppm
addtile

Which feels about right. I assume since I didn't define any values it went to the defaults. However, it would be great to know the actual values so I have a base from which to make adjustments.


A couple other questions if I may: I've found that dirt.ppm, grass.ppm, and sand.ppm are built in tile textures. Are there others?
Second, since the tilemap doesn't actually show in the game when covered by decals, I was thinking of making the texture for each surface a 2x2 px solid color to minimize file size. Is there any reason not to do this?

Thanks!
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Re: Ground Friction and Resistance Index

Postby ShackAttack12 » Mon Sep 19, 2016 6:30 pm

I'd like to discuss traction in more detail since there seems to be a huge bias towards supermoto style traction in MXS. Or maybe someone can prove to me that a 1.5 coefficient of friction is actually accurate for a motocross tire on dirt?

The traction from 2012 Supercross actually isn't that slick, settings wise. The roll resistance is much less than more modern traction, which actually promotes less WFO style of riding but allows the bike to carry more speed (is that really a bad thing?).

Code: Select all

2012 Supercross - A1 Traction
friction 1.0 1.0
friction 1.0 32.0
friction 1.5 64.0
roll_resist 5.0 15.0 10.0


This setting yields a 1.0 coefficient of friction up to 32ft/sec of rear tire slip, which is 21mph.
Then, the coefficient of friction increases linearly to 1.5 from 32ft/sec (21mph) up to 64ft/sec (~43mph) of slip.

I actually think this traction configuration is more than you'd see in real life. 1.5 coefficient of friction when the rear tire is rotating 43mph faster than the front? 1.2 CoF is the actual maximum of rubber on asphalt that i have seen in literature. Even considering a brand new motocross tire with knobbies digging into the dirt, you're telling me that a stationary motocross tire spinning 43mph on dirt has 25% more traction than rubber on asphalt?

Here's a diagram from a paper (READ THIS: http://www.tandfonline.com/doi/pdf/10.1 ... 014.985804) i was reading on road tire dynamics in various conditions. This paper is talking about braking performance, but the same principles should apply for acceleration performance. Notice that a rubber road tire on dry asphalt has a max CoF of 1.2 at around 15% tire slip (the slip ratio is essentially a percentage, ie .1 is 10%), after which it tapers off.
Image

And this makes sense when you watch slow motion drag videos.... you'll see the tires are actually slipping about 10-15% to obtain maximum traction:


I have been searching for some good data on offroad tire traction and it seems hard to come by (and if anyone can find some, please post it), probably because there are so many factors involved (terrain sheer, force, contact patch, etc).

I'd have to guess that on extremely hard dirt (i'm talking blue groove) the CoF for a motocross tire would have to be in the 0.7-0.8 range. On ideal terrain dirt with the perfect about of terrain sheer where your tire can bite in and with perfect treaded tires, i'd guess you would see something like 0.9 or so, but definitely nowhere near the 1.2 CoF that is rubber-to-asphalt. On wet/muddy terrain the CoF would probably be down in the 0.5-0.6 range.

Again, if i'm way off on this, convince me otherwise.
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Re: Ground Friction and Resistance Index

Postby jlv » Tue Sep 20, 2016 2:24 am

1.5 is too high. 1.25 @ 48 f/s would have been better for the last line. I was trying to be forgiving.

You can take a decent guess by watching the lean angle in a corner. The coefficient of friction should be a little more than the tangent of the lean angle assuming the rider is going as fast as possible. When you watch flat corners in pro races they're usually leaning around 45 degrees.

Wouldn't be too hard to make a poor man's tire dyno. It'd basically consist of dragging a weighted tire around at various speeds with a hanging scale to read the force.
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Re: Ground Friction and Resistance Index

Postby ShackAttack12 » Tue Sep 20, 2016 7:55 pm

jlv wrote:1.5 is too high. 1.25 @ 48 f/s would have been better for the last line. I was trying to be forgiving.

You can take a decent guess by watching the lean angle in a corner. The coefficient of friction should be a little more than the tangent of the lean angle assuming the rider is going as fast as possible. When you watch flat corners in pro races they're usually leaning around 45 degrees.

Wouldn't be too hard to make a poor man's tire dyno. It'd basically consist of dragging a weighted tire around at various speeds with a hanging scale to read the force.


I went ahead and did a crude experiment to figure out the corresponding lean angles for various friction coefficients. Without knowing where and how much exactly the Center of Mass/Total Mass is for the bike+rider combo, these numbers are going to be off a little (and maybe you can chime in with the actual numbers?). I basically just pinned the bike in 1st gear with a very high roll damping and limit factor, and leaned over slowly until the front tire started to turn in (lose traction), and then measured the angle of the rear tire respective to the ground at that point of slip.

Image

And just to illustrate how i took the crude measurement:
Image

I think we can say that 45 degrees has to be the absolute maximum for even on the stickiest of dirt compounds, so really the static friction in any tilemap should not be higher than 0.8. What do you think?
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Re: Ground Friction and Resistance Index

Postby onefoureight » Tue Sep 20, 2016 8:09 pm

ShackAttack12 wrote:Slippery traction yadayada


I know you've been looking for a way to slow down the game, and looking at the traction from that perspective, you would actually slow down the game quite a lot as we'd have to soften our suspension so we'd actually get grip.

Softer suspension means massive risk when sending big lines, (Easy legs off).

I'm currently running 100 fork compression dampening on SX and I'm having little to no front end slide because I can push it into the corners with the current traction.

I know for sure if the traction was at .8 there's no way I could run 100 without sliding out.

TL;DR: Slippery Traction = Softer more realistic suspension.
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Re: Ground Friction and Resistance Index

Postby ShackAttack12 » Tue Sep 20, 2016 8:25 pm

onefoureight wrote:
ShackAttack12 wrote:Slippery traction yadayada


I know you've been looking for a way to slow down the game, and looking at the traction from that perspective, you would actually slow down the game quite a lot as we'd have to soften our suspension so we'd actually get grip.

Softer suspension means massive risk when sending big lines, (Easy legs off).

I'm currently running 100 fork compression dampening on SX and I'm having little to no front end slide because I can push it into the corners with the current traction.

I know for sure if the traction was at .8 there's no way I could run 100 without sliding out.

TL;DR: Slippery Traction = Softer more realistic suspension.


That's actually my point. With the friction settings used on recent tracks, we are able to get away with so much unrealistic stuff. Realism needs to begin with the traction.
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Re: Ground Friction and Resistance Index

Postby M@xTizZz » Tue Sep 20, 2016 10:32 pm

ShackAttack12 wrote:
jlv wrote:1.5 is too high. 1.25 @ 48 f/s would have been better for the last line. I was trying to be forgiving.

You can take a decent guess by watching the lean angle in a corner. The coefficient of friction should be a little more than the tangent of the lean angle assuming the rider is going as fast as possible. When you watch flat corners in pro races they're usually leaning around 45 degrees.

Wouldn't be too hard to make a poor man's tire dyno. It'd basically consist of dragging a weighted tire around at various speeds with a hanging scale to read the force.


I went ahead and did a crude experiment to figure out the corresponding lean angles for various friction coefficients. Without knowing where and how much exactly the Center of Mass/Total Mass is for the bike+rider combo, these numbers are going to be off a little (and maybe you can chime in with the actual numbers?). I basically just pinned the bike in 1st gear with a very high roll damping and limit factor, and leaned over slowly until the front tire started to turn in (lose traction), and then measured the angle of the rear tire respective to the ground at that point of slip.

Image

And just to illustrate how i took the crude measurement:
Image

I think we can say that 45 degrees has to be the absolute maximum for even on the stickiest of dirt compounds, so really the static friction in any tilemap should not be higher than 0.8. What do you think?


wow! very instructive,
IMO 45 degrees is too low to be the maximum, it really depends on which ruts and depth of ruts.
When you scrap the ground with the end of your bar it's more 70 degree, i know you can't do it every corners, but i would say something like 65/70 degrees is a realistic maximum.
I still think 1.2 is a good base for hardpack tracks at this time (i mean with the way of how traction evolve in this game, it's still not enought slippery to be realistic but just my opinion ...)
going from 1.22 to 1.25 for softer soil or just watered soil
1.30 for sand tracks (+ roll resist way different)

here for example, it's more than 45 degrees and it doesnt look that soft just a deep rut :

Image
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Re: Ground Friction and Resistance Index

Postby M@xTizZz » Tue Sep 20, 2016 10:42 pm

Sorry for dp
But this :
jlv wrote:Wouldn't be too hard to make a poor man's tire dyno. It'd basically consist of dragging a weighted tire around at various speeds with a hanging scale to read the force.


could really change how you "feel" the traction in game, i'm sure we could stay reasonable on our friction if it's possible to set a tyres pression or something similar
but here 0.8 as friction is really not possible at this time, i don't think the screenshots you posted Shack is taking care about the structures of the tyres or the pressure settings
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Re: Ground Friction and Resistance Index

Postby ShackAttack12 » Tue Sep 20, 2016 10:57 pm

M@xTizZz wrote:
wow! very instructive,
IMO 45 degrees is too low to be the maximum, it really depends on which ruts and depth of ruts.
When you scrap the ground with the end of your bar it's more 70 degree, i know you can't do it every corners, but i would say something like 65/70 degrees is a realistic maximum.
I still think 1.2 is a good base for hardpack tracks at this time (i mean with the way of how traction evolve in this game, it's still not enought slippery to be realistic but just my opinion ...)
going from 1.22 to 1.25 for softer soil or just watered soil
1.30 for sand tracks (+ roll resist way different)

here for example, it's more than 45 degrees and it doesnt look that soft just a deep rut :

Image


The picture you posted, the bike is almost perpendicular to the rut face, so he's essentially just G'ing out instead of leaning over (like a banked turn). His bike is probably only leaning over 15 or so degrees relative to ground where the tire is contacting.

You see, the terrain is so fricken smooth in MXS that track creators then have to compensate with unrealistic friction to allow the bike to lean over. If we had realistic ruts (and MXS physics allowed the bike to stick in the rut), we wouldn't need unrealistic friction numbers, and you'd have to pick your lines better. What a concept!
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Re: Ground Friction and Resistance Index

Postby jlv » Wed Sep 21, 2016 1:27 am

M@xTizZz wrote:IMO 45 degrees is too low to be the maximum, it really depends on which ruts and depth of ruts.
When you scrap the ground with the end of your bar it's more 70 degree, i know you can't do it every corners, but i would say something like 65/70 degrees is a realistic maximum.
I still think 1.2 is a good base for hardpack tracks at this time (i mean with the way of how traction evolve in this game, it's still not enought slippery to be realistic but just my opinion ...)
going from 1.22 to 1.25 for softer soil or just watered soil
1.30 for sand tracks (+ roll resist way different)

here for example, it's more than 45 degrees and it doesnt look that soft just a deep rut :

http://motocross.transworld.net/wp-content/blogs.dir/441/files/2008/12/02/tuestip_12_21.jpg

When there's banking in the form of a berm or rut you can achieve any lean angle regardless of friction as long as the banking is steep enough. When trying to guesstimate friction from lean it has to be a flat corner.

ShackAttack12 wrote:You see, the terrain is so fricken smooth in MXS that track creators then have to compensate with unrealistic friction to allow the bike to lean over. If we had realistic ruts (and MXS physics allowed the bike to stick in the rut), we wouldn't need unrealistic friction numbers, and you'd have to pick your lines better. What a concept!

I'm not so sure about that. Tiny ruts are extremely difficult even in real life where you can feel them. A lot of the reason to use high friction is to let you save it when you over/undershoot a rut.

Slippery is just harder in general. More realistic but more frustrating.
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Re: Ground Friction and Resistance Index

Postby Ezra » Wed Sep 21, 2016 4:53 am

Also, i feel like the tire collisions being as large as they are makes small ruts quite difficult, as theres no real way to get a tire to "stick" in a rut, really its just like a bunch of little berms, with the tire behaving as a sphere on an incline plane...
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