Anyone ever used this model? How is it?

http://cgi.ebay.com/eMagin-Z80 ... ZWDVWQQrdZ1QQcmdZViewItem

I too have a hard time with the view that LFS is too expensive. Good grief, I'd pay a lot more for it than they're charging. Spent probably double that last night at the bar for three hours of entertainment

I've spent probably pennies on the hour for the entertainment that LFS has provided, not to mention the perks like having some fun folks to chat with here in the forums from time to time

Want expensive? Try our game:

http://www.virtualrc.com/eshop/eshop.aspx?pcid=1

We charge $120 for the base game pack which doesn't include all the tracks. Those are extra. Granted, Virtual RC Racing is more of a niche thing. RC racers are used to spending a ton on their hobby, so most of them view it as well worth it in comparison to a weekend of racing.

Anyone recall the two movies with those 3D virtual reality type glasses awhile back showing LFS? They were really impressive. I think I'd like to get a set if they aren't $10,000 a pop or something. Can anyone recommend a good set that's maybe $500 or less? I don't think I really want shutter glasses (tried them, very cool indeed), but the full head motion type of thing with the LCDs right over your eyes. Anyone have experiences with these? That'd be just nuts to play with

I couldn't get it to work anyway. Doesn't seem to like my cam for some reason. I'm also not a fan of moving the camera direction while driving. With a flight sim it'd be cool, but I like a pretty rigid camera in racing sims.

I haven't tried this myself yet, but apparantly you can use your web cam with this software to do a mouse/headtracking sort of thing. Perhaps a poor man's version of TrackIR? If it works well, maybe Scawen could pop it in to LFS as an option if there isn't already a mouse-look type of thing there somewhere.


http://www.download.com/Track/ ... 10644879.html?tag=lst-0-5

Got a 133 here too. Missed 3 of the questions. The one about the fruit, the 16 shaded boxes pattern, and the one about the two guys travelling at 2 average speeds to point x and y. I missed the "and back" part so got that wrong. Doh! Still, I'm happy with 100 percentile in all categories.

Interestingly enough I had taken this same one probably a couple of years ago and got the same score.

Right, hence my comment "Ignoring the high frequency ringing and other artifacts..."

Tough to ignore of course especially through headphones, but the idea is that eventually it will of course be eliminated.

Not sure if this helps identifying codecs and what not (I'm no video wizard), but the video was made with Windows Movie Maker.

That's a bummer Do you have Windows Media Player 10 installed? Works fine on that for me.

Quote from JTbo :

Can't say that there is now error at all in frequency, it is quite lot of work to adjust correctly in sample based engines at least, lot of testing and comparing or that is what I had to do.

By the way, there is a method to the madness when it comes to finding the rpm of a recorded sample. What I do when working with samples is run a program that plays a sine wave with a frequency controlled by a scrollbar at the same time the recorded engine sample is playing in a loop. Just adjust the frequency to match and resonate with the recorded sample and then you can calculate the rpm quite accurately from that.

I posted somewhere else here on how to do that if I'm not mistaken. If you're interested a search might turn up that thread. The idea is that the base frequency where it resonates equals how many exhaust pulses you have per second. So considering # of cylinders and whether it's a 2 stroke or 4 stroke engine it's easy to calculate. If there's interest maybe I can put up a little proggy to play the sine wave and show the rpm directly after you input # of cylinders and 2/4 stroke. Any interest, folks?

Ok, you were right after all. I know what the problem was. The previous examples were (supposedly if I wasn't making a mistake, which is entirely possible) running the left/right banks of the engine through the left/right speakers. The idea was that a dual exhaust system would sound like that. Apparantly I must not have been doing it right, which would cause the frequency to be a lot lower than it should have been.

The new video there has both banks combined running through both speakers. That does sound a lot better, more natural, and bumps up the frequency to where it should be. Thanks for pointing that out. That was good constructive criticism

Will check out your links.

Quote from AndroidXP :

On a sidenote, does your sim support separate throttle/brake axes? From the looks of the black bar it still seems to be combined. Might be interesting how it handles trailbraking, etc.

It's combined right now. Virtual RC Racing had no need for split axis so I didn't include it. I'll add it though. Will need it for KartSim for sure anyway

Quote from JTbo :

Then real life is off too, 5k rpm really does not sound so low in any car I have seen and heard IRL, whatever reason is behind it. LFS may too have engine sound spot on as it is generated on fly, but still it sounds too low compared to RL cars, can't say why it is so, but it just is

Maybe it is ok for 1cyl engine, more cylinders tend to give sound feeling that there are more rpm than less cylinders, or maybe some additional sound like intake/exhaust, don't really know what makes it, but my ears are telling me, there is that much missing and my ears are adjusted to RL engines

Nonetheless, it is very impressive piece of software you are building there and I follow it with great interest

edit: Just did remember that I did some recordings for my mod some time ago, recorded with videocam so really not too great sound quality and perhaps not too useful for anything else than my mod I think.

Thanks for the input. What do you think of this one? Better or worse? Ignoring the high frequency ringing and other artifacts...

Edit: Accidentally posted 22a.wmv again. Here's the new one:

http://www.performancesimulations.com/files/ToddSim23a.wmv Niels: This one is at 50fps I think. The capturing process doesn't effect the sound frequency so that's not the thing.

Last edited by jtw62074, Fri, 9 Mar 2007 20:30.

Hysterical, thanks for the link

When I was a kid the neighbor kids had three parrots. We were sitting around talking/playing/watching TV or whatever we were doing when suddenly we heard another kid laughing in the kitchen (it sounded exactly like the little brother in the house, but he was sitting right next to us). Then another.. Then another... Took me a minute to realize the parrots were doing it. This caused us all to start laughing which just egged the birds on even more. So here are four or five of us kids and three birds laughing hysterically at absolutely nothing. It was a great moment!

The LFS devs aren't the only devs to have suffered the Wrath of Kid. What goes on in the forums is only part of the story in one other case I know of (see avatar ). It doesn't surprise me in the least to see that he conducted himself the same way with the LFS devs. I'm quite frankly shocked he was ever involved with LFS in any way.

Anyway, good riddance as far as I'm concerned

You might try googling "C++ sine wave audio example." My engine audio stuff started from an example of playing a calculated sine wave through the speakers, which is a nice, simple place to start.

I haven't looked much at this link, but maybe it'll help.

http://nsound.sourceforge.net/

Quote from JTbo :

Rpm sounds to be too low, I know it is just temporarily thing, but it still sounds too low, 1500rpm higher would be perhaps nice

The rpm is actually spot on. The audio is generated and driven by a pretty complex engine simulation I wrote awhile back. The base frequency matches exactly. It's all the other sims you play that are off

New one:

http://www.performancesimulations.com/files/ToddSim22a.wmv

Neat tool, Becky. Thanks for sharing. My creator (not Bob's) just let you choose a straight or a turn, followed by the length, turn radius, and number of degrees to turn along with the degree step that decides how fine the mesh is. It was all just a single triangle strip and doing elevation changes required manually typing in the height value. Yuck Bob's is light years ahead of mine

Quote from Bob Smith :

Interesting sounds there Todd. Does look a little nicer than before, has there been much other progress since vids of old?

Not much has been done really in awhile. I work on it in spurts now and then. I had ordered a G25 wheel just after someone referred me to Bob's Track Builder, so I spent a day getting those tracks loaded and rendered. The wheel arrived the next day so I got the clutch and h-shifter running in it. I'm having a blast with it Unfortunately I don't have any FFB coded in yet though. That would take it to another level and be really fun so am looking forward to it. Some day..

Piddy: There's no visible tire flex there. The tires are done with splines in real time so it should be fairly straightforward to distort things however is necessary and make them match the deformations in the physics model. When I do that maybe I'll post another video at the tire, although I must admit getting it as good as it is in LFS will be a challenge I'm planning on writing a new tire model (again) so will probably wait on the visual deformation stuff until then as the new model will be a bit better suited to it.

Hi guys,

I bought Bob's Track Builder ( http://www.bobstrackbuilder.net/images/screenshots.aspx ) and altered my sim to import the x files and textures it creates. This is a really handy tool for creating tracks and has made things much more interesting for me. Finally I have something roughly resembling "modern" graphics

http://performancesimulations.com/files/ToddSim21c.wmv (16MB)

This is the first public video running my artificial engine sound simulation too, btw. Unfortunately I can't play any other sounds at this point while that's running, so there is no tire squeal or differential whine here.

Anyway, just something a little new to show

Discussion thread:

http://forum.rscnet.org/showthread.php?p=3389502#post3389502

Quote from axus :

Niels - as Todd said, those tests are from aged tyres. Modern tyres are much stiffer and hence peak at lower slip angles/slip ratios.

I will direct him to this thread once he wakes up though .

Too late, Axus. I found it on my own

Quote from Niels Heusinkveld :

OT.. well on LFS :O)

That huge post of Todd.. About the feel of 'break away' being more related to the stop of force buildup and not a curve that drops.. Can I apply this to LFS for a moment?

There have been acceleration and braking tests in LFS and it was very hard to do better than a 'complete wheelspin' start or a 'locked tyres' stop. This might indicate, ever so perhaps, that the rise of the curves in LFS is on the steep side? I know the curves don't drop much in LFS, which is probably the main reason that its the best sim 'once it goes wrong' but the buildup seems very quick. Its easy to go from no wheelspin to loads of wheelspin in an instant, and in a turn, the difference between going through it smoothly and leaving skid marks is tiny.

Any thoughts on this?

My comments on break away were in reference to lateral/cornering forces rather than longitudinal. The picture in longitudinal is similar, but it doesn't quite pertain to what you're referring to directly.

High slip ratios do indeed usually cause a drop in longitudinal force after the peak for reasons I won't get into here (I need to keep some things to myself for my model ). If the amount of acceleration you're getting when spinning the wheels is too high, then indeed the longitudinal curves could be tweaked to provide more of a drop off. I doubt very much that this is due to a flaw in the LFS tire model. It's most likely just a matter of tweaking parameters to get some slightly different curves.

Same goes for braking of course. In reality it's not quite that simple as temperature and other things effect it too making the picture quite dynamic, but a very good approximation can still be made with fixed curves. This is after all how it's done in the racing industry. If it's good enough for them it's probably good enough for us What people want is to have increased stopping distances when you lock a tire up. That can probably be accomplished with some tweaking.

In one dynamic test I saw, at the instant of lock-up the tire was still providing quite a lot of force, almost as much as you get at the peak. It then trailed off to a lower value over a small period of time, so the curves in reality are not really fixed. Again, a completely locked tire is a different situation than one that's rolling a little bit but still at a high slip ratio. The patch of rubber in the contact zone is not getting a chance to cool off through a revolution of the tire, but is instead sitting there being absolutely fried. Back it off to slip ratio -0.9 (-1.0 is fully locked) and the picture is quite different.

Anyway, all they need to do to get a really good approximation is to get the longitudinal curves to drop off a bit more (not the lateral ones though!). That'd be close enough for government work

I'd venture to guess that Kid was mistakenly trusted by the guys at one time.

Yeah, I edited out my comment. Found the link just before you posted.

Yep, me too.

The reason for this is something called "tire load sensitivity." When you stiffen the bar and increase the vertical force a bunch on one tire, the lateral force goes up, yes, but the friction coefficient of that tire goes down.

In physics 101 it's taught that Coulomb friction is how everything works. I.e, the friction coefficient (let's call it "mu") is constant between two surfaces, such as a chunk of wood on smooth tile. This is pretty close to true when dealing with hard materials, but it's not correct for tires or other things made of rubber even on hard surfaces.

Imagine the two rear wheels. If Coulomb friction actually held true for tires and their friction coefficient (mu) with the road was 1, the amount of side force each of the tires could produce would be the same as the vertical force or load on them. So in a case where you have little weight transfer (your soft rear ARBs) on an axle with a weight of 1000, you might have vertical loads like this:

Inside tire 400
Outside side 600

The maximum cornering forces are also 400 and 600 (multiply the vertical load by mu, in this case 1). So total cornering force at the rear is 1000. If you then stiffen the rear end so you get a lot more weight transfer, you might have vertical loads like this:

Inside tire 100
Outside tire 900

If mu stays at 1 then you still have the same overall cornering force on that axle of 100 plus 900, or 1000. So really, if tires worked that way ARB's wouldn't do much of anything at all to the handling balance.

Tires have that "load sensitivity" mentioned earlier. This is just a fancy phrase meaning that the friction coefficient (mu) varies with the vertical force. I.e., it doesn't stay constant at 1 or some other number all the time. If you increase the vertical force, mu drops. The cornering force for that tire will of course increase, yes, but it does not increase in proportion to the vertical force increase. If you double the vertical load, the cornering force almost doubles too, but not quite. The inside tire produces less force since it's less loaded, but produces just a bit more than it otherwise would since its friction coefficient goes up. However, the outside tire loses more than the inside tire gains, so in the end you have less overall cornering force on that axle. Harder springs or ARBs will then make things more slippery on that axle.

If mu changed with load something like this:

Load
100 1.12
400 1.08
600 1.05
900 1.00

And we look at our soft and hard rear ends again (that doesn't sound right ) we will have different overall cornering forces for each one.

Soft:

Inside tire 400 load means mu = 1.08, so cornering force for this tire is 400*1.08=432
Outside side 600 load means mu = 1.05, so cornering force for this tire is 600*1.05=630

Total cornering force at the rear with the soft rear setup is 630 + 432 = 1062.

If we switch to the hard anti-rollbar we have a different situation because of this load sensitivity:

Inside tire 100 load means mu= 1.12, so cornering force for this tire is 100 * 1.12 = 112
Outside tire 900 load means mu = 1.00, so cornering force for this tire is 900 * 1.00 = 900

That gives us a cornering force of 1012 at the rear (900+112). This is actually less than the 1062 we get with the softer set up, so we tend to get more oversteer when we stiffen up the rear.

This phenomenon is pretty much the only thing that makes chassis tuning at the limit possible at all in most cars

Last edited by jtw62074, Thu, 18 Jan 2007 06:01.