GeoGebra model of GPB bike model

[HornetMaX]

WARNING: (fairly basic) math/geometry inside. Number-allergic people can skip 

Hi all,

I think I managed to create some sort of visual representation of the .geom file of GPB. Two important points first:

• This stuff is messy, hence I'm not 100% sure it is correct. Looks correct to me, but only Piboso could confirm. I doubt he'll waste his precious time to do this (and I can't blame him for that decision) so ...
• Thanks to neoraptor, who had the initial (and smart) idea to use GeoGebra for that task !

You can use GeoGebra in your browser (GeoGebra Web) but the standalone application (Downloads) works better for me. In any case, it's free.

I've attached the .ggb file: it contains the 990 data in the "Spreadsheet".
If you want to change some data manually it is possible. If youwant to put another .geom model, do this:

• Copy/Paste the entire .geom file (except the collision sections) into Excel/ or similar (I used LibreOffice)
• Normally it will ask you to parse the data as a fixed/delimited file: use dleimited with "=" and "," as separators.
• Now select all the lines between "type" and "t-cam" (4 columns, A-D), copy it and thenm paste it into GeoGebra Spreadsheet (starting from the right cell, A4).
• You will have to enter manually the wheel sizes (front, rear) in cells B1 and B2: you can find them in GPB .tyre files (at the end, "Radius").

The sliders allow to change the bike configuration: SwingArm length, SwingArmPivot (no effect in GPB at the moment) and Rake are bike's parameters, while FLength and SwingRot are the "state" of the suspensions (how much the front fork is extended and how much the rear swingarm is rotated).

There are 2 bikes shown: the one the top is in the chassis reference frame, the wheels do not touch an horizontal line.
The one on the bottom is in the "world" frame: here the road is horizontal and the wheels are on it.

On the top part you have the individual components in their own reference system. You cam move them moving around the O* points (no impact on anything).

One thing you can see is how the various parameters influence important quantities as Wheelbase, effective rake, trail etc.

One thing I don't know at all , is what "rear_length" does in the .geom file. It seems to have no effect at all.

MaX.

[JC#21]

thx Max and Neo 

This allow us to figure out how works geom in gpbikes 

I have 2 questions now :

1) How should I put the chassis, the fork and the swing arm in 3dsmax scene before export ?
2) How should I collect all the coordinates points ?
3) is there a specific point defines as reference who would be at the center of the 3dsmax scene univers ? or can we just put the model as we want and after define the new location of each points ?

[HornetMaX]

I have 2 questions now :

Cheater

1) How should I put the chassis, the fork and the swing arm in 3dsmax scene before export ?

I have no idea: 3d modelling is really something I do not plan to look into, no time for that.
But for sure our modders know, given we already have plenty of bikes working.
For my tool it doesn't really matter, as far as iot is OK for GPB.

2) How should I collect all the coordinates points ?

Which coord points ? The O* (O_sw, O_fu, O_st, O_ch) ?

These are just offsets to be able to move the components around.
In the .geom file they are all assumed to be in (0,0), then each component is moved to its correct position.

3) is there a specific point defines as reference who would be at the center of the 3dsmax scene univers ? or can we just put the model as we want and after define the new location of each points ?

Can't answer this. I suspect that in 3ds you'll have to model/export each part separately and each will have his own reference point. In the .geom file, the points of a component are relative to that reference point. Example:

• Swingarm in 3ds has reference point O_sw in (5,5) (let's keep it 2d). The swingarm joint is 1 left of this point, so in (4,5).
• In the .geom file, the coord of the joint will be (-1,0).
• In my tool you can move around O_sw as you want, but the joint will always be 1 left of O_sw

MaX.

[JC#21]

Max have you understand this part of the geom file ?

Code Select Expand

rip_leftpos = -0.25, 0.2, -0.1
grip_leftdir = 1, 0, 0
grip_rightpos = 0.25, 0.2, -0.1
grip_rightdir = 1, 0, 0

I have tried to change the values but nothing change ingame

other question, I would like create the box colision with this information :

Code Select Expand

box0 = 0, -0.05, -0.45, 0.33, 0.18, 0.5, 0.19

but do you know how it works ? how should I read it ? length, width, height, ... 

[JC#21]

It's ok for the box code except the last 0.19.

For the other codes, I have no idea :-(

[HornetMaX]

Looks like the hands position (in some reference frame) but ...

Maybe ODi knows (not sure from what I see in his .geom files).

But Piboso may know

MaX.

[JC#21]

Do you know what is the pressure_center ?

[HornetMaX]

Do you know what is the pressure_center ?

The pressure center is the point at which the aerodynamic forces are applied (and around which axes the aero moments are applied).

MaX.

[JC#21]

The pressure center is the point at which the aerodynamic forces are applied (and around which axes the aero moments are applied).

MaX.

thx Max

Sometimes I feel like this


I'm gonna search more information about it and geom of motorcycle in general

[HornetMaX]

I'm gonna search more information about it and geom of motorcycle in general

Here: http://forum.piboso.com/index.php?topic=1165.0

MaX.

[Alone]

It's ok for the box code except the last 0.19.

For the other codes, I have no idea :-(

I think that is the radious of the sphere.

[HornetMaX]

It's ok for the box code except the last 0.19.

For the other codes, I have no idea :-(

I think that is the radious of the sphere.

The radius of the sphere in a box ?

MaX.

[Alone]

I think that is the radious of the sphere.
[/quote]

The radius of the sphere in a box ?

MaX.
[/quote]

hahaha, I feel like an idiot  Bad read, I thought that he was asking for the fsusp...so, no idea 

[BOBR6 84]

Noob question.. Can I use GeoGebra to adjust the tyre size/shape in-game?

Or are changes to the 3d model and everything else needed too?

Be kind lol 

[HornetMaX]

Noob question.. Can I use GeoGebra to adjust the tyre size/shape in-game?

No.

Or are changes to the 3d model and everything else needed too?

It depends: do you want the tyre to look bigger or to feel (behave) bigger ?
For the 1st it's the 3d model, for the 2nd its the physics.

Be kind lol 

I'm always kind, no ? 

MaX.