Hi !

Back in Montreal i’m working again on our shoulder model…

I just have a little (for you i hope) problem.

Let me explain : I have a new coordinate system on the scapula, wich

is define to be as in the new ISB recommendations. Its origin is now

on the AA point and it’s rotated of 90 degrees around the y axis.

(This system is used to replace positions of points on the humerus,

recorded in our in vitro experiments. The humerus then is driven by

the positions of the points and not Anybody’s Mannequin file.)

We defined it like that in the Joints&Drivers file with John :

Main.Model.HumanModel.Right.ShoulderArm.Seg.Scapula.aa = {

AnyRefNode ISBOrigin = {

sRel = {0,0,0};

ARel = RotMat(pi/2,y);

AnyDrawRefFrame drw = {

RGB={1,1,0};

ScaleXYZ = {1,1,1}/5;

};

};

};

There is no problem with this. After that I defined a similar system

on the humerus and applied a calculation with the rotational sequence

we use to measure angles during the movement :

Main.Model.HumanModel.Right.ShoulderArm.Seg.Humerus.gh = {

AnyRefNode ISBAxes = {

sRel = {0,0,0};

ARel =

Main.Model.HumanModel.Right.ShoulderArm.Seg.Scapula.aa.ISBOrigin.ARel;

// ARel = RotMat(pi/2,y);

AnyDrawRefFrame drw = {

RGB={0,1,1};

ScaleXYZ = {1,1,1}/5;

};

};

};

[… and then calculation …]

But the thing i want to do is fixing a coordinate system on the

humerus, centered on GH, which would be the same than the scapula one

at t=0 (I mean that at t=0, coordinate systems of humerus and scapula

are parallel). With that I would have angles set at 0 in all

directions at the beginning of the motion.

I tried but when i modified the axes, i modified the humerus position.

This new coordinate system would be used only to mesure angles with

the desired rotation sequence, so I don’t care about the present

humerus system and don’t wanna change it if that changes the bone

position.

May it be possible to add one like I described ?

Thanks a lot

Sincerely,

Yoann