StandingModel InitialPositions.any

In the “InitialPositions.any” file for StandingModel, what are
the ‘x’, ‘y’, and ‘z’ in RotMat refering to? From what I can gather
observationally, they initially refer to the global coordinates (x -
anterior, y - superior, z - lateral) located at the origin of the
humerus, but then they move with the humerus through each rotation (so
therefore order matters). Is this correct? Or are the axes used
almost the same direction as global? If this is the case, how do find
the direction of these rotational axes?

Nick

Hi Nick

the x,y and z in RotMat is refering to the axis that the first
argument is rotating around.
I am not sure I understand you correct, but the initial positions is
the position you want the model to stand in after it is loaded. The
initial position does not change during the kinematic movements.

Best Regards Christian

— In anyscript@yahoogroups.com, “stl_nick_gt” <nflieg@…> wrote:
>
> In the “InitialPositions.any” file for StandingModel, what are
> the ‘x’, ‘y’, and ‘z’ in RotMat refering to? From what I can gather
> observationally, they initially refer to the global coordinates (x -
> anterior, y - superior, z - lateral) located at the origin of the
> humerus, but then they move with the humerus through each rotation (so
> therefore order matters). Is this correct? Or are the axes used
> almost the same direction as global? If this is the case, how do find
> the direction of these rotational axes?
>
> Nick
>

Hi Christian,

I’m pretty sure that I understand the mechanics of the RotMat
command, but I am unsure as to what the x,y and z axes are referring
to. Are they global, or the local of the humerus? In context from
the InitialPositions.any file:

//right humerus
ref.Right.ShoulderArm.Seg.Humerus.Axes0 =
ref.Trunk.SegmentsThorax.ThoraxSeg.Axes0*
ref.Trunk.SegmentsThorax.ThoraxSeg.ij.ARel*
ref.Trunk.SegmentsThorax.ThoraxSeg.ij.RotNode.ARel*
RotMat((pi/180)JointPos.Right.GlenohumeralFlexion ,z)
RotMat((pi/180)JointPos.Right.GlenohumeralExternalRotation ,y)
RotMat((pi/180)JointPos.Right.GlenohumeralAbduction ,x)
ref.Right.ShoulderArm.Seg.Humerus.gh.RotNode.ARel’*
ref.Right.ShoulderArm.Seg.Humerus.gh.ARel’;

It is not immediately clear what coordinate system the x,y, and z
are with respect to.

Nick

— In anyscript@yahoogroups.com, “Christian Gammelgaard”
<cgol03@…> wrote:
>
> Hi Nick
>
> the x,y and z in RotMat is refering to the axis that the first
> argument is rotating around.
> I am not sure I understand you correct, but the initial positions
is
> the position you want the model to stand in after it is loaded. The
> initial position does not change during the kinematic movements.
>
> Best Regards Christian
>
> — In anyscript@yahoogroups.com, “stl_nick_gt” <nflieg@> wrote:
> >
> > In the “InitialPositions.any” file for StandingModel, what are
> > the ‘x’, ‘y’, and ‘z’ in RotMat refering to? From what I can
gather
> > observationally, they initially refer to the global coordinates
(x -
> > anterior, y - superior, z - lateral) located at the origin of
the
> > humerus, but then they move with the humerus through each
rotation (so
> > therefore order matters). Is this correct? Or are the axes used
> > almost the same direction as global? If this is the case, how
do find
> > the direction of these rotational axes?
> >
> > Nick
> >
>

Hi Nick

The rotations are wrt to the global ref. of the system in this case.
The RotMat will just provide a rotation matrix and it is what you
use it for which will decide if it is wrt to local or global
cooridnate systems.

So in this case where we set the Axes property of the segment it is
wrt to the global system, but if we had applied the rotation to an
ARel of an node on a segment it would be the coordinate system of
this node.

I when the lines below says:
RotMat((pi/180)JointPos.Right.GlenohumeralFlexion ,z)
it will rotate the segment around the global z axis

then it is mulitplied by the rotmat

RotMat((pi/180)*JointPos.Right.GlenohumeralExternalRotation ,y)

which is then effectively a rotation wrt. to already rotated syetem.

So it is only the first rotation which is wrt. to the global
coordinate system.

Best regards
Søren, AnyBody Support

— In anyscript@yahoogroups.com, “stl_nick_gt” <nflieg@…> wrote:
>
> Hi Christian,
>
> I’m pretty sure that I understand the mechanics of the RotMat
> command, but I am unsure as to what the x,y and z axes are
referring
> to. Are they global, or the local of the humerus? In context
from
> the InitialPositions.any file:
>
> //right humerus
> ref.Right.ShoulderArm.Seg.Humerus.Axes0 =
> ref.Trunk.SegmentsThorax.ThoraxSeg.Axes0*
> ref.Trunk.SegmentsThorax.ThoraxSeg.ij.ARel*
> ref.Trunk.SegmentsThorax.ThoraxSeg.ij.RotNode.ARel*
> RotMat((pi/180)JointPos.Right.GlenohumeralFlexion ,z)
> RotMat((pi/180)JointPos.Right.GlenohumeralExternalRotation ,y)
> RotMat((pi/180)JointPos.Right.GlenohumeralAbduction ,x)
> ref.Right.ShoulderArm.Seg.Humerus.gh.RotNode.ARel’*
> ref.Right.ShoulderArm.Seg.Humerus.gh.ARel’;
>
> It is not immediately clear what coordinate system the x,y, and z
> are with respect to.
>
> Nick
>
> — In anyscript@yahoogroups.com, “Christian Gammelgaard”
> <cgol03@> wrote:
> >
> > Hi Nick
> >
> > the x,y and z in RotMat is refering to the axis that the first
> > argument is rotating around.
> > I am not sure I understand you correct, but the initial
positions
> is
> > the position you want the model to stand in after it is loaded.
The
> > initial position does not change during the kinematic movements.
> >
> > Best Regards Christian
> >
> > — In anyscript@yahoogroups.com, “stl_nick_gt” <nflieg@> wrote:
> > >
> > > In the “InitialPositions.any” file for StandingModel, what are
> > > the ‘x’, ‘y’, and ‘z’ in RotMat refering to? From what I can
> gather
> > > observationally, they initially refer to the global
coordinates
> (x -
> > > anterior, y - superior, z - lateral) located at the origin of
> the
> > > humerus, but then they move with the humerus through each
> rotation (so
> > > therefore order matters). Is this correct? Or are the axes
used
> > > almost the same direction as global? If this is the case, how
> do find
> > > the direction of these rotational axes?
> > >
> > > Nick
> > >
> >
>