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mightycucumber
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mightycucumber
Special Super Pro
Joined: November 12th, 2012, 2:12 am

December 19th, 2014, 3:12 pm #11

Gotta give this a good read when I have time again. There's always new things to be learned, awesome guide! ;)
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Citywalker
Re-Volt Chieftain
Citywalker
Re-Volt Chieftain
Joined: January 26th, 2010, 3:30 am

December 24th, 2014, 3:26 pm #12

Hey, great work, Gel!
Still, some corrections are in order.

• ResMod: (“as if the car weighs more on the right or left side”)
This is not correct. What I have found is that ResMod simply modifies the AngRes while in air. Make it 25 and the car stops rotating (tumbling) in air 25 times sooner than realistic (like flying in syrup). Make it 1 and the car tumbles in air like it realistically should. Make it 0 and the tumbling never slows until it hits the ground. Make it -1 and tumbling accelerates in air.
Heavier left or right side comes only from CoM placement.

• EngineRate: (“Numbers above 4.5 make no difference”)
Well, they do make a difference. It’s useful for extremes, like a wheelie-popper / dragster. It’s just the normal cars that have no reasonable difference above 4.5.

• MaxPos: (“a setting of 1 will cause an extreme amount of understeer”)
I have not seen that. In fact, even if it did, a little lower 2nd Inertia would cure this.
•• (“Increasing this number in excess of 50 - 100 seems to encourage a heavier, more simulation feel of the car.”)
I think that feel comes simply from the car swaying more on springs, instead of being flat and then suddenly flipping over when the grip threshold is exceeded.
A more pronounced heavier/lighter feel can be set with slightly higher/lower 1st and 3rd Inertia values.
A warning here: a MaxPos 50 or something with even slightly soft springs makes the car’s wheels bump right through the bonnet when landing and stoop off the body completely when in air (too long spring travel).

• Stiffness, Damping, Restitution:
My experience seems to tell a bit different story.
+ Stiffness controls how high the car sits on springs – 100: flat on wheels, 1000: at spring zero-point (wheel attachment point) on rock-hard springs, everything in-between: bouncing on various heights (with Body Mass 1 – adjust linearly for different Mass).
And it didn’t seem to be affected by wheel base.
+ Damping does depend on wheelbase. Wider wheelbase needs lower Damping, or wheels will shake.
+ Restitution: the only thing I have been able to guess that this does, is control the spring’s decompression, i.e. how fast it lengthens without load or how strong it pushes the car up.
••• Still, this is my empirical experience only and the truth may be somewhere between me and Gel38.

• Additional AI notes: (“Thus, if your car is a motorcycle with only 2 wheels, the car will only use the AI settings which the track tells the car, and not the AI Details.”)
You can actually cure this, by making the bike have technically 4 wheels: 2 front ones in same spot and 2 rear ones in same spot. Just halve the Stiffnesses and EngineRatios then.
•• [shameless plug] And if the AI parameters seem too complex, use the simple FringeAI tuning method (called ExpertAI at RVZ), so you just set 2 values and change 1 value in two places (tutorial, helper spreadsheet).[/shameless plug].

So, that’s my 22 cents :)

All in all, kudos for this new version of parameter notes, Gel!
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gPstr
Junior RC
gPstr
Junior RC
Joined: December 13th, 2014, 7:52 pm

December 24th, 2014, 6:31 pm #13

Citywalker,Wednesday, Dec 24 2014 wrote: <snip>
Some quick comments, just because I don't want to miss the chance to discuss parameters:

I'd agree that it's not true that EngineRate above 4.5 makes "no" difference, but it does generally make little that I've been able to see. I sometimes adjust it mostly on a whim, but at this point, I usually don't bother. I haven't played with it much at extremes though.

MaxPos does have an effect on handling, but it's secondary - it doesn't directly affect it, but rather the fact that the springs can travel further affects it, since it means that the body can lean and bounce more (or less, as the case might be). It doesn't necessarily mean that it will - just that it can if the rest of the settings encourage it. And MaxPos can indeed lead to unrealistic spring travel - the wheels clipping through the body for instance - but that's easily dealt with by making it legitimate. The difference between a point at or near the closest point on the body with which the wheels will intersect and the point at which the wheels normally ride equals the MaxPos - the maximum distance the shocks can travel before the wheel hits the body.

Re: Stiffness - primarily, it seems to be just what it seems it should be - the actual stiffness of the springs. And as far as I can tell, that's in all directions - it not only affects how easily the springs will compress, but how much they'll sway. It's true that it does affect ride height, but as far as I can tell, that's secondary - softer springs and/or greater mass means the springs are already compressed to some degree, lowering the normal ride height. When I build a car with a lot of body sway, like my RC18T, I first get all the suspension numbers where I want them for the behavior I want, then I adjust the Y axis wheel placement to get the base ride height I want.

Damping is still the least explicable of the suspension settings, but the basic gist seems correct as far as I can tell - it, however it does it, affects the tendency of the shocks to compress or decompress - the ease and the speed with which they'll do it. Most of my work with Damping has been to try to get it balanced correctly with Stiffness - I treat it more as a modifier of Stiffness than as a significant setting on its own.

I think you're exactly right about Restitution, and the fact that you commented on it, and correctly as far as I can see, is most of why I wanted to respond. "Restitution" is in fact the movement back to an earlier state, and in considering suspension, it is in fact the force with which the spring "pushes back" under compression. And that seems to be exactly the case in Re-Volt. As a good example, look at the jumping behavior of a car with relatively soft suspension and relatively high restitution, like Harvester. As they go up a jump the springs compress from the change in direction, then as they're leaving the top of the ramp, the springs decompress, and more forcefully than they compressed, making the car pitch forward since the rear wheels are the last part in contact with the ground. Lowering Restitution or raising stiffness can fix that (though it can lead to other consequences). And as with real cars, much can be done with restitution. For instance, increasing rear spring restitution (and front stiffness to compensate) - so that the rear springs push down harder against the ground and thus pivot the body on the X axis, and the front springs can handle the additional load - can fix understeer.

I'm pleased that all through your comments, you refer back to changes in the Inertia matrix. I think the correct Inertia matrix is absolutely crucial to good parameters, and it disappoints me to see so many cars with a copy and paste of Toyeca's numbers. Those are almost always the first numbers I change when I'm trying to fix a car with poor handling. And like the wheel Friction numbers, big changes are usually a poor fix and result in unrealistic handling. Precise numbers, and numbers in a particular relationship with each other, are the keys.

I know next to nothing about AI and rely on you for all my insight into that.
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Gel38
Expert Re-Volter
Gel38
Expert Re-Volter
Joined: October 27th, 2013, 11:49 am

December 24th, 2014, 11:20 pm #14

Gathering info here. But to comment in return:

I agree (mostly) on MaxPos. A setting of 50+ will cause the tires to go thru the car indeed. As far as understeer, I have had the issue. While, the inertia matrix can be adjusted, it makes the car 'bigger', as Inertia is supposed to relate to the actual size of the car. (I set inertia matrix to the track-width and wheelbase.

As far as Stiffness, The trackwidth/wheelbase thing, I remember when working on "Choochoo" I had a problem getting the car to set right, and I ended up lowering the stiffness and damping...It could be that I got the 2 settings confused with taking in the trackwidth and such into account. - Also, it does indeed control the ride-height of the car.

On Restitution, I DO BELIEVE, I got lazy here and copy-pasted from the original param notes. So you could very well be right (Sorry, so far here, i'm talking to Citywalker)

With ResMod, What I mean with that setting is, it can create a bit of instability (tumbling in air).. And the reason I put it the way I did, reverts to real life (2007 [American] Ford Fusion) Going over fast humps the Fusion will pull to the right (as if unstable in a jump) In real life this is caused by weight distribution from left to right. My description was to give an idea of what the effect is.

With the AI, Making a 2 wheel car a 4 wheel car is possible, but that's a fix, and I thought about adding that bit to the notes, but it was a fix, and not an actual function which occurs by adjusting a setting. So it was left out.

Oh, and Let's not forget the Engine rate. That bit of info from you (citywalker) will be added in. Some info is from the original notes, and some is from personal research.

Not that i'm ignoring gPster here, He basically posted the same stuff, however, I will take a look at these settings in the coming days ahead and post an update. (I've still got a couple projects in the works)

Thanks guys :D
AM-Bio Design Car and Level Design.
Don't let the car drive you. You drive the car. - American Motors Bio Motto

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gPstr
Junior RC
gPstr
Junior RC
Joined: December 13th, 2014, 7:52 pm

December 25th, 2014, 7:35 pm #15

Sorry - yeah - you probably can pretty much ignore my post, since it was more just me indulging an opportunity to prattle on a bit about some of the things I've figured out about parameters - it wasn't stuff directly related to this incarnation of the ParamNotes.

Re: Inertia - trackwidth and wheelbase are a good part of it (and height, and, if pertinent, overall width and length). It also has to be proportional to mass though. Toyeca-style Inertia (1400/2200/700) is acceptable for a mass of 2.0, but generally too much for a lighter car and too little for a heavier one. To respond realistically, they have to have Inertia numbers that match with the weight.

Re: Wheelbase and Track and such - I'd say that you're both right, and more. All of the suspension settings depend to some degree on wheelbase and track, just because physics. Essentially, as far as the suspension is concerned, the car is a lever, the suspension is its end point and the CoM is its fulcrum. Basic physics says that the longer a lever is, the greater the force it requires and generates. That needs to be considered with the suspension settings.

Re: Restitution - as I said, Citywalker's observations on Restitution is most of what inspired me to respond, because nobody that I'd seen before seemed to really understand it, and no Parameters Notes yet has dealt with it well. I noted that in this one too, but I just sort of let it slide, since it would require a lot of explanation to make sense of it, and I'm not certain that my observations are fully correct, so I wasn't willing to try to foist them on someone else. But yeah - I'm certain that the primary effect of Restitution is to determine the force with which the suspension "pushes back" under compression.

Busy - gotta go...
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Gel38
Expert Re-Volter
Gel38
Expert Re-Volter
Joined: October 27th, 2013, 11:49 am

December 27th, 2014, 9:52 am #16

Parameters Notes 7 download has been updated. (Forum versions still need updating)

A link has been provided at the very top of the Thread.

Corrections include:

Offset1 (for wheels): more information added about XYZ directions and effect of Ride height on the Z axis; Photo Added.

Inertia (for car body): Removed the letter 'I' in one of the formulas

Misc. Info section: Added in the CTRL+R function of RV 1.2

Spring stiffness: added note about the effect of ride-height adjustment.

ResMod: Added a small note about in-air stability for further clarification.

MaxPos (for tires): Added note about numbers in excess of 50 can cause tires to come through the body.

Damping: Spelling correction; added note about taking wheel-base, track-width into account.

Offset (car body): Corrected which numbers relfected the Y and Z axis.

Offset (springs): Corrected which numbers relfected the Y and Z axis.

Offset (spinner): Corrected which numbers relfected the Y and Z axis.

Offset (aerial): Corrected which numbers relfected the Y and Z axis.
AM-Bio Design Car and Level Design.
Don't let the car drive you. You drive the car. - American Motors Bio Motto

American Motors Bio
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Citywalker
Re-Volt Chieftain
Citywalker
Re-Volt Chieftain
Joined: January 26th, 2010, 3:30 am

December 27th, 2014, 3:34 pm #17

To continue the discussion:

Of course Inertia depends on Mass also, and linearly so (i.e. if you use an Inertia value 1400, 2200, 700 with a car that weighs 2 kg and then double the car’s weight to 4 kg, you will need to double all Inertia values as well, to 2800, 4400, 1400).

Levers: a small correction – the longer a lever is, the _smaller_ the force it requires and the _greater_ the force it generates. Still, that’s probably a good way of thinking why a longer wheelbase needs less Damping. But why wheelbase affects Inertia, is probably not from physics at all – in RV code, Inertias are calculated by quaternions... Pure math.
All my stuff is available here, and all my videos are available there.
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gPstr
Junior RC
gPstr
Junior RC
Joined: December 13th, 2014, 7:52 pm

December 28th, 2014, 12:39 am #18

Mm... yeah. That lever analogy sort of got away from me. I knew there was something wrong in there somewhere, but I couldn't quite put my finger on it.


And yeah - you're right about it ultimately being math rather than physics, but I'd say that distinction is sort of academic as far as this goes. It can't be physics anyway, since it's not really real. It is math and ultimately couldn't be anything other than math. But it's math used to (hopefully) model physics, so to as great a degree as it's done well, it can be approached as "physics," even if it's technically not. But yes, it is purely math, really.

And yes - of course inertia depends on mass as well as size, but no ParametersNotes yet has actually said so. For a long time, they didn't really deal with the inertia matrix at all. Then they started running the current version, with the size explanation, which is at least a step in the right direction, but still insufficient. The problem though is that I don't really know how it all works, aside from the obvious fact that it depends on both size and mass, so I haven't been (and am still not) willing to go so far as to insist that it should include... something. I've done it enough that I have a pretty good feel for the basic settings based on mass and the specific proportions based on the proportions of the car, but it's pretty much by feel, and always has to be tested and refined. There's no way to simply say, "This is how it works," so I don't. Other than to make the point that it relies on mass as well as size. I tend to think there's a basic MR² calculation in there somewhere, but I haven't been able to isolate it.


Oh and briefly, to Gel38 (if you made it this far) - a clarification - any MaxPos that allows the wheel to travel far enough to clip through the fender will lead to... the wheel clipping through the fender. Too much MaxPos can indeed cause clipping, but I'm not sure if it's wise to specify a number for that "too much," since it actually depends on the specific situation. I have one car I'm working on lately with which the wheels clipped through the hood with a MaxPos of 6, just because it's that low-slung and has that little clearance.

/nitpicking.
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Gel38
Expert Re-Volter
Gel38
Expert Re-Volter
Joined: October 27th, 2013, 11:49 am

December 28th, 2014, 9:21 am #19

(Deleted the first section, as, I was only mildly frustrated by the comment, but not so fed-up as I was in the comment. I was actually frustrated by stuff outside of RV. So, I'm sorry for the previous lines that stood here)

Anyway,

And truly, A lot could be done with Inertia, I understand it, but parameters notes is more about defining everything in a simple (or, semi-simple) manor for people to understand. If everything should be taken into account, we need a cross-reference notes, showing every detail of how you can fix certain problems. As stated above (but simpler here), Param notes is merely a definition of what each function does.

And yeah, MaxPos, I understand that the wheel will pop thru the top of the car at different numbers, as, it depends on how tall the car actually is. 50 was just a quote from Citywalker, which, for normal cars is FAIRLY accurate. (still pops thru at 45). Perhaps I will correct this.

Again, sorry for the earlier rant.
AM-Bio Design Car and Level Design.
Don't let the car drive you. You drive the car. - American Motors Bio Motto

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gPstr
Junior RC
gPstr
Junior RC
Joined: December 13th, 2014, 7:52 pm

December 28th, 2014, 5:41 pm #20

Probably a good thing that I didn't read whatever was there before.

And see... this is why I started out on this thread just complimenting your quality job and offering up one little suggestion that I thought could be simply dealt with - because I understand that the point of the parameters notes is to just briefly outline "this number does this" instead of to go into all the excruciating detail of what does what to what when and how this interacts with that and blah blah blah.

Then, against my better judgment, I started prattling. And I knew I was prattling - I knew I was droning on about information that nobody else much cares about anyway and that has no place in this, but I did it anyway.

I have little doubt that whatever was there before was deserved, and I apologize for hijacking the thread.
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