body offset

[atis-7]

hello

i working with ODE about 3 years ago and now i would like integrate
ODE into an 3d engine, but i am running into a wall:

This 3d engine doesn't render their nodes at center of mass. i.e.: if
i rendering a cube at (0,0,0) then one of corner be at origo and NOT
mass centre.

I think about 3 days ago "never mind" i will offset ode bodies (or
geoms) with half length of corner and so it will work fine. Other
physics engine it is just a routine: (i.e: in Newton:
collision=NewtonCreateBox(nWorld,size.x,size.y,size.z,
0,&offsetTransform(0,0)); or in Physx: boxDesc.localPose.t = NxVec3
(translation.x, translation.y, translation.z);)

I tried many ode apis but in vain i couldnt offset bodies or geoms
with center off mass.

Any idea?

Atis

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[Daniel K. O.-2]

atis escreveu:
> This 3d engine doesn't render their nodes at center of mass. i.e.: if
> i rendering a cube at (0,0,0) then one of corner be at origo and NOT
> mass centre.

Just about any 3D engine let you use any point as a reference; usually
through a tree of scene nodes, where child scene nodes have coordinates
relative to their parents. Does this 3D engine lack this mechanism?

Also, if the built-in boxes have such weird point of reference, can't
you just load/draw a mesh for a symmetric box around its origin?


> I think about 3 days ago "never mind" i will offset ode bodies (or
> geoms) with half length of corner and so it will work fine.

I don't see why you would need to fix anything in ODE's side. You just
have to set the box's position (in the 3D engine) with the proper offset.


> I tried many ode apis but in vain i couldnt offset bodies or geoms
> with center off mass.

You can't offset the center of mass. The body's center is, by design,
its center of mass.



--
Daniel K. O.
"The only way to succeed is to build success yourself"

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[atis-7]

thx the answer

On Oct 18, 11:43 am, "Daniel K. O." <danielko.lis...@...> wrote:
> atis escreveu:
>
> > This 3d engine doesn't render their nodes at center of mass. i.e.: if
> > i rendering a cube at (0,0,0) then one of corner be at origo and NOT
> > mass centre.
>
> Just about any 3D engine let you use any point as a reference; usually
> through a tree of scene nodes, where child scene nodes have coordinates
> relative to their parents. Does this 3D engine lack this mechanism?

editor of 3d engine cant offset the objects so if i create a world
with offsetless :) and after that i load it and render according to
ode geom positions plus offset by 3d engine it cause different object
coordinate in editor and gaming.

> Also, if the built-in boxes have such weird point of reference, can't
> you just load/draw a mesh for a symmetric box around its origin?
>
> > I think about 3 days ago "never mind" i will offset ode bodies (or
> > geoms) with half length of corner and so it will work fine.
>
> I don't see why you would need to fix anything in ODE's side. You just
> have to set the box's position (in the 3D engine) with the proper offset.

becouse it would be a very clean solution and every physics api know
it.

i hope next release of ode will implement this feature too

> > I tried many ode apis but in vain i couldnt offset bodies or geoms
> > with center off mass.
>
> You can't offset the center of mass. The body's center is, by design,
> its center of mass.

:) its so sad!!!

Atis
>
> --
> Daniel K. O.
> "The only way to succeed is to build success yourself"
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[Jon Watte (ODE)-2]

atis wrote:
> editor of 3d engine cant offset the objects so if i create a world
> with offsetless :) and after that i load it and render according to
> ode geom positions plus offset by 3d engine it cause different object
> coordinate in editor and gaming.
>
>  

So fix the editor? Or fix the layer that goes between the editor and
ODE. When going from engine to ODE (which is on scene load) then offset
one way. When extracting position when going back to engine, offset the
other way.


Note that, in general, you want to use artist-created meshes, rather
than built-in primitives. Artist-created meshes can


--

  Revenge is the most pointless and damaging of human desires.


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[Jon Watte (ODE)-2]

atis wrote:
> i hope next release of ode will implement this feature too
>
>  

If all you want to do is get a specific position relative to the mesh
out of ODE, all you have to do is use dBodyGetRelPointPos() instead of
dBodyGetPos() when you read out the position. However, in general, it's
better to let the scene graph handle this offset if needed, rather than
ODE. Given that this function does exactly what you want, I don't think
any new feature needs to be implemented :-)

Sincerely,

jw


--

  Revenge is the most pointless and damaging of human desires.


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[atis-7]

do we discuss this problem in two forums? :)

i will analyze your advice and let you know the result

On Oct 19, 10:47 pm, Jon Watte <jwa...@...> wrote:

> atis wrote:
> > i hope next release of ode will implement this feature too
>
> If all you want to do is get a specific position relative to the mesh
> out of ODE, all you have to do is use dBodyGetRelPointPos() instead of
> dBodyGetPos() when you read out the position. However, in general, it's
> better to let the scene graph handle this offset if needed, rather than
> ODE. Given that this function does exactly what you want, I don't think
> any new feature needs to be implemented :-)
>
> Sincerely,
>
> jw
>
> --
>
>   Revenge is the most pointless and damaging of human desires.

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[atis-7]

in progress

i sux with immovable (no body objects) and rotation, but i see the
light the end of road.

3d engine offset is a wrong solution because i would like mixing ode
controlled and not ode controlled objects.

On okt. 20, 11:24, atis <szomba...@...> wrote:

> do we discuss this problem in two forums? :)
>
> i will analyze your advice and let you know the result
>
> On Oct 19, 10:47 pm, Jon Watte <jwa...@...> wrote:
>
>
>
> > atis wrote:
> > > i hope next release of ode will implement this feature too
>
> > If all you want to do is get a specific position relative to the mesh
> > out of ODE, all you have to do is use dBodyGetRelPointPos() instead of
> > dBodyGetPos() when you read out the position. However, in general, it's
> > better to let the scene graph handle this offset if needed, rather than
> > ODE. Given that this function does exactly what you want, I don't think
> > any new feature needs to be implemented :-)
>
> > Sincerely,
>
> > jw
>
> > --
>
> >   Revenge is the most pointless and damaging of human desires.- Idézett szöveg elrejtése -
>
> - Idézett szöveg megjelenítése -

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