[ODE] Gravity
Charles Ingalls
Charles Ingalls" <charles.ingalls at freesbee.fr
Tue May 13 11:27:01 2003
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Hi,
Thanks to all for answering me...
I'll give you more details:
My object is a box (1,1,1). I considere unit is 1 for 1 meter.
The object fall from 10 to 0 (always in meter).
The mass and density are 1 unit (without air friction, there is no =
interaction with the speed of falling, isn't it ?).
I use a gravity value of -9.8.(m/s/s not ?)
Now my simulation work with a timestep 0.01 with a refresh of 85 FPS but =
I use the 'repeat' system witch give me exact 100 call to dWorldStep so =
100 * 0.01 =3D 1 second (whaouu ;-) ).
And my box always fall like it was on the moon...:-(
I've look at 'test_boxstack.cpp' in ODE Package and found that gravity =
is set to -0.5 (????) and timestep to 0.05 (????).
Someone could explain me the meaning of this value and where is my =
problem ???
Thanks,
Charles.
----- Original Message -----=20
From: Sean Cullen=20
To: Charles Ingalls ; ode@q12.org=20
Sent: Tuesday, May 13, 2003 1:30 PM
Subject: RE: [ODE] Gravity
This is true if the units of your objects are in meters. If they =
happen to be setup in Feet then you would want -32 instead of -9.8. =
Also it is assuming that you are using seconds as your timestep. Do you =
step 100 times/sec with 0.01?
-----Original Message-----
From: ode-admin@q12.org [mailto:ode-admin@q12.org]On Behalf Of =
Charles Ingalls
Sent: Tuesday, May 13, 2003 7:16 AM
To: ode@q12.org
Subject: [ODE] Gravity
Hi,
If I set dWorldSetGravity (dWorldID, 0, 0, -9.8);
with a timestep of 0.01,
the objects are falling very slowly...(like on the moon).
Could someone explain me why ???
This -9.8 means 9.8 m/s/s isn't it ?
Thanks,
Charles.
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<DIV><FONT face=3DArial size=3D2>Hi,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks to all for answering =
me...</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I'll give you more =
details:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>My object is a box (1,1,1). I considere =
unit is 1=20
for 1 meter.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>The object fall from 10 to 0 (always in =
meter).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>The mass and density are 1 unit =
(without air=20
friction, there is no interaction with the speed of falling, isn't it=20
?).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>I use a gravity value of -9.8.(m/s/s =
not=20
?)</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Now my simulation work with a timestep =
0.01 with a=20
refresh of 85 FPS but I use the 'repeat' system witch give me exact =
100=20
call to dWorldStep so 100 * 0.01 =3D 1 second (whaouu ;-) =
).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>And my box always fall like it was on =
the=20
moon...:-(</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I've look at =
<EM>'test_boxstack.cpp'</EM> in ODE=20
Package and found that gravity is set to -0.5 (????) and timestep =
to 0.05=20
(????).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Someone could explain me the meaning of =
this value=20
and where is my problem ???</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Charles.</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DSean.Cullen@lmco.com =
href=3D"mailto:Sean.Cullen@lmco.com">Sean=20
Cullen</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dcharles.ingalls@freesbee.fr=20
href=3D"mailto:charles.ingalls@freesbee.fr">Charles Ingalls</A> ; <A=20
title=3Dode@q12.org href=3D"mailto:ode@q12.org">ode@q12.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, May 13, 2003 =
1:30 PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: [ODE] =
Gravity</DIV>
<DIV><BR></DIV>
<DIV><SPAN class=3D415522711-13052003><FONT face=3DArial =
color=3D#0000ff size=3D2>This=20
is true if the units of your objects are in meters. If they =
happen to be=20
setup in Feet then you would want -32 instead of -9.8. Also it =
is=20
assuming that you are using seconds as your timestep. Do you =
step 100=20
times/sec with 0.01?</FONT></SPAN></DIV>
<DIV><SPAN class=3D415522711-13052003><FONT face=3DArial =
color=3D#0000ff=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D415522711-13052003></SPAN> </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px =
solid; MARGIN-RIGHT: 0px">
<DIV class=3DOutlookMessageHeader dir=3Dltr align=3Dleft><FONT =
face=3DTahoma=20
size=3D2>-----Original Message-----<BR><B>From:</B> <A=20
href=3D"mailto:ode-admin@q12.org">ode-admin@q12.org</A>=20
[mailto:ode-admin@q12.org]<B>On Behalf Of </B>Charles=20
Ingalls<BR><B>Sent:</B> Tuesday, May 13, 2003 7:16 AM<BR><B>To:</B> =
<A=20
href=3D"mailto:ode@q12.org">ode@q12.org</A><BR><B>Subject:</B> [ODE] =
Gravity<BR><BR></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Hi,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial><FONT size=3D2>If I set <FONT=20
color=3D#0000ff>dWorldSetGravity (dWorldID,=20
0, 0, -9.8);</FONT></FONT></FONT></DIV>
<DIV><FONT face=3DArial color=3D#0000ff size=3D2><FONT =
color=3D#000000>with a</FONT>=20
<FONT color=3D#000000>timestep of 0.01,</FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>the objects are falling very =
slowly...(like on=20
the moon).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Could someone explain me why =
???</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>This -9.8 means 9.8 m/s/s isn't it=20
?</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial=20
size=3D2>Charles.</FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>
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