Why nodeIndex is always -1 for player model???

Hi, everybody,

I came across one problem with my player model which caused my program crashed, and I traced back and found below situation:

In tsShapeInstance.h (around 850 lines?Maybe not because I've changed much with my codes):

inline MatrixF * TSShapeInstance::ObjectInstance::getTransform()
{
return nodeIndex<0 ? NULL : smTransforms + nodeIndex;
}

For my player model, nodeIndex is always -1. Why? How to change the value and make it correct?

What does nodeIndex mean? Should I change my model and how to do that?

Anyone may help?

Thanks a lot,