[ODE] Units used by ODE
Keshav
kbc at dhruva.com
Wed Aug 14 07:58:02 2002
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Hello,
I was wondering in which units the ODE library works?
Is it in the world_units or meters??
I'm trying to implement a car using ODE.
My problem is something like this:
My world gravity is 0.0, -2.5, 0.0.
If I set the gravity to -9.8, then, the car becomes very unstable.
What should be the right gravity to set?
I have a car whose length, width and height are say 2.5, 1.0 and 3.0
meters respectively.
Say, the mass is about 600kg, hence the weight is (600 * 2.5) = 1500kg.
I have four wheels for my car.
I start simulating, and everything goes on fine.
The dimensions for the car are very less in terms of 3D units. It's too
small.
So, I scaled my car's dimensions by 20 times, assuming each meter equals
20 generic 3D units.
I scaled even the wheel parameters (by 20 times) to match the car.
(PLEASE LET ME KNOW IF I'M doing anything WRONG here)
Now, when I simulate, the result is very different from the original.
When I have scaled the car evenly,
shouldn't it behave the same way?
Also, I would like to know, in which units force is measured?
- Keshav.
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<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial=20
size=3D2>Hello,</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial size=3D2>I was =
wondering in=20
which units the ODE library works?</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial size=3D2>Is it =
in the=20
world_units or meters??</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial size=3D2>I'm =
trying to=20
implement a car using ODE.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>My problem is something like this:</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>My=20
world gravity is 0.0, -2.5, 0.0.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>If I=20
set the gravity to -9.8, then, the car becomes very=20
unstable.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>What=20
should be the right gravity to set?</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>I have=20
a car whose length, width and height are say 2.5, 1.0 and =
3.0=20
meters respectively.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>Say,=20
the mass is about 600kg, hence the weight is (600 * 2.5) =3D=20
1500kg.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>I have=20
four wheels for my car.</FONT></SPAN></DIV></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>I=20
start simulating, and everything goes on fine.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>The dimensions for the car are very less in terms =
of 3D units.=20
It's too small.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>So, I=20
scaled my car's dimensions by 20 times, assuming each meter equals =
20=20
generic 3D units.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>I=20
scaled even the wheel parameters (by 20 times) to match the=20
car.</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2><STRONG>(PLEASE LET ME KNOW IF I'M doing anything WRONG=20
here)</STRONG></FONT></SPAN></DIV></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>Now,=20
when I simulate, the result is very different from the original. When I =
have=20
scaled the car evenly,</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial color=3D#0000ff =
size=3D2>shouldn't it behave the same way?</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial size=3D2>Also, =
I would like=20
to know, in which units force is measured?</FONT></SPAN></DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D960482107-13082002><FONT face=3DArial size=3D2>-=20
Keshav.</FONT></SPAN></DIV></DIV></BODY></HTML>
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