WIP - Brno Track surface Rebuild.....

[HornetMaX]

Hmm ... something still buggers me in the reasoning.

The "minimum resolution of quads spanning the track width" is necessary only if the track (the 2m long slice of track) is not planar, otherwise one quad should be enough.
Unless you have some sort of camber, then a single quad should be enough (length of the quad should depend on the change of slope, of course).

Anyway, it would be nice to have Piboso's word on this subject as this would save a lot of time to our track modders.

MaX.

[Hawk]

Hmm ... something still buggers me in the reasoning.

The "minimum resolution of quads spanning the track width" is necessary only if the track (the 2m long slice of track) is not planar, otherwise one quad should be enough.
Unless you have some sort of camber, then a single quad should be enough (length of the quad should depend on the change of slope, of course).

Anyway, it would be nice to have Piboso's word on this subject as this would save a lot of time to our track modders.

MaX.

Yes one quad does sound logical if the surface was flat, doesn't it.

It takes no more time to model a higher count of quads in a track mesh than it does for just one. 

I agree,  it would be nice if Piboso could enlighten us on the this subject. In particular how the collision detection model he is using works. 

[HornetMaX]

It takes no more time to model a higher count of quads in a track mesh than it does for just one. 

No, but it takes more .. humm... quads, which may or may not be a problem (FPS) in game.

Just trying to figure out if the improvement comes from the fact you've used more quads laterally (to span the width) or from the fact that your quads are simply laid out better, or more uniformly or whatever.

MaX.

[Hawk]

It takes no more time to model a higher count of quads in a track mesh than it does for just one. 

No, but it takes more .. humm... quads, which may or may not be a problem (FPS) in game.

Just trying to figure out if the improvement comes from the fact you've used more quads laterally (to span the width) or from the fact that your quads are simply laid out better, or more uniformly or whatever.

MaX.

From my tests(both low resolution, high, and in between), a high resolution of quads(on tight corners) seems to be required at this time for bike stability while cornering especially, as I said,  for those tight corners. I think the stability comes from a combination of both the quads being uniformly spaced out without any distortion of those quads. As far as I understand, it also helps with the stability of the collision detection also.

I'm actually wondering if the physics of the tyre model still needs tweaking to help cornering stability on uneven surfaces, because at this time it feels like the tyre physics are modelled in such a way that it is riding on a knife edge(were the slighted unevenness while healed over is causing the tyres to slid away. In reality the tyre is not riding on an edge it is riding on a patch of rubber(not sure of it's size) as the tyre deforms under load. I'm sure you are better qualified to tell us the technical details of the mechanics of this process. 

[LauZzZn]

If you want to see how to get a perfect surface, just open tracked, then open phillip island and set wireframe you see the track mesh then

[Hawk]

If you want to see how to get a perfect surface, just open tracked, then open phillip island and set wireframe you see the track mesh then

Hi LauZzZn.

This being correct then your statement suggests pointing to the physics needing to be still tweaked to a final solution, as even on Phillip Island there is bike instability while cornering, in particularly  at turn 10, but instability also happens on turn 4 at times too.

I have had a good look at the Phillip Island track mesh, and it's good, but with all respect, it's not perfect. Some of the quads are distorted as though someone had created the track surface and then needed to shift one side of the track at places to line the quads up with the terrain quads? I have to ask, "What was the need to do that?".

Also, in my tests, it's definitely a case that on tight corners a surprisingly high quad count on those sections definitely brings stability to a bike while cornering in a tight corner section. Plus I found that a minimum 4 quad span of the track surface width in other places like the straights seems to add to a feeling of stability as a whole in the feel of the bikes. This being the results of my tests, I respectfully have to ask the question: "Is the Victoria mesh really as perfect as you suggest?". 

[janaucarre]

Months ago i made curve test, a rectangular track, with descent and rise, ultra regular dispatching polygons and with no tilt, all was very good, the bike never has any problem, the problem begins when i add tilt in curve, so the problem can come from the non regular poly but mainly with the tilt.
The problem is definitively a physic problem.

[HornetMaX]

I'm actually wondering if the physics of the tyre model still needs tweaking to help cornering stability on uneven surfaces, because at this time it feels like the tyre physics are modelled in such a way that it is riding on a knife edge(were the slighted unevenness while healed over is causing the tyres to slid away. In reality the tyre is not riding on an edge it is riding on a patch of rubber(not sure of it's size) as the tyre deforms under load. I'm sure you are better qualified to tell us the technical details of the mechanics of this process. 

Well, Piboso probably doesn't want to disclose the exact tire model he's using (and that's understandable), but he said he uses some sort of Pacejka model which, as far as I know, is pretty much a standard for tire simulation.
The tire model consist (roughly) of:

• a roliing resistance (irrelevant for our discussion here)
• a yawing moment (around a vertical axis)
• an overturning moment (around a longitudinal axis)
• a vertical force that balances the load
• a longitudinal force (traction or braking) normalized with respect to the vertical load, as function of the longitudinal slip
• a lateral force normalized with respect to the vertical load, as function of a sideslip angle

What we are interested in are the last two: each is described by a graph (longit. normalized force vs longit. slip and lateral normalized force vs sideslip angle).
On each graph you typically have multiple lines, parametrizing the curve in the camber angle (lean angle). In fact, the graphs also depends on other stuff (e.g. tire pressure and temperature).

The nice thing is that the curves have more or less always the same shape, so that a particular set of equations with a bunch of parameters can describe to a very reasonable level of accuracy the particular curve you want to have, just playing with the parameters.

In reality, tires are tested (on a funky machine with one large rotating disc simulating the road, a real tire + wheel put on it, on a mechanical arm measuring forces and moments), data is collected (the graphs) and then you fit the parameters to obtain the model: an empirical approach but it gives good results.

The model "hides" inside the equations and parameters all the very complex effect it would be hard to model more precisely (at our level of detail), like for example the patch size or the carcass deformation.

Months ago i made curve test, a rectangular track, with descent and rise, ultra regular dispatching polygons and with no tilt, all was very good, the bike never has any problem, the problem begins when i add tilt in curve, so the problem can come from the non regular poly but mainly with the tilt.

What do you mean with "tilt" ? Banked turns ?

MaX.

[janaucarre]

The translate i found for inclinaison was tilt, wasńt sure it was the right term, you are probably more right with banked. The exterior of the curve is higher or lower than the interior.

[Hawk]

Months ago i made curve test, a rectangular track, with descent and rise, ultra regular dispatching polygons and with no tilt, all was very good, the bike never has any problem, the problem begins when i add tilt in curve, so the problem can come from the non regular poly but mainly with the tilt.
The problem is definitively a physic problem.

When you say adding tilt in the surface produces problems, are you talking about adding camber in the track surface?

[HornetMaX]

Yeah, banked is what you mean.

I think we could do a very nice test on this "banked turn" thing using Dijon Prenois: turn #4 (the tight 180 degrees, called "parabolique").
The bike really spins on itself in that turn.

I think JC21 has the original files, so ...

MaX.

[Hawk]

Yeah, banked is what you mean.

I think we could do a very nice test on this "banked turn" thing using Dijon Prenois: turn #4 (the tight 180 degrees, called "parabolique").
The bike really spins on itself in that turn.

I think JC21 has the original files, so ...

MaX.

Agreed.... would be a good test. I'll look into it. 

[janaucarre]

i have the original files of dijon.

[Hawk]

i have the original files of dijon.

Hi Janu.

Lol.... I've just PM'd JC concerning this. LOL

Would it be possible to send me a download link? It would be interesting to see the results of this test Max suggested.

[janaucarre]

i will send you all what you need, this night i mean.