Specifications

26
Try loading the model again and have a look at the graphical representation. If you zoom out enough, you
should see your points floating around the ellipsoid connected to its center of gravity by yellow pins.
One segment does not make much of a mechanism, so let's define a forearm as well. In the segs folder, add
these lines:
AnySeg ForeArm = {
Mass = 2.0;
Jii = {0.001,0.01,0.01};
AnyRefNode ElbowNode = {
sRel = {-0.2,0,0};
};
AnyRefNode HandNode = {
sRel = {0.2,0,0};
};
AnyRefNode Brachialis = {
sRel = {-0.1,0,0.02};
};
AnyRefNode Brachioradialis = {
sRel = {0.0,0,0.02};
};
AnyRefNode Biceps = {
sRel = {-0.15,0,0.01};
};
AnyRefNode Triceps = {
sRel = {-0.25,0,-0.05};
};
AnyDrawSeg DrwSeg = {};
}; // ForeArm
}; // Segs folder
When you reload the model you may not be able to see that the forearm has been added. In fact it is there,
but it is placed exactly on top of the upper arm and since the two segments have similar mass properties, it
is impossible to see which is which.
Before we proceed it might be worth thinking a bit about why objects get placed the way they do in the
model and how we can control the placement. The first thing to notice is that we are in the process of
making a model of a living organism which supposedly will move about changing its position all the time. So
there really is no "right" placement of a segment in the model. The second thing to notice is that even if we
are able to exercise some control over the placement of objects, then at least we have not done so yet. So
this is why the system for lack of better information places both segments at the origin of the global
reference frame at load time.
What eventually will happen is that we will define joints to constrain the segments with respect to each
other and also drivers to specify how the mechanism will move. When all that is done, these specifications