20 lines (13 with data), 582 Bytes

SegmentsLumbar.PelvisSeg.r0 = {JointPos.PelvisPosX,JointPos.PelvisPosY,JointPos.PelvisPosZ} 
                              - SegmentsLumbar.PelvisSeg.AnatomicalFrame.sRel*SegmentsLumbar.PelvisSeg.Axes0';

#ifdef PelvisRotMat
SegmentsLumbar.PelvisSeg.Axes0=
JointPos.PelvisRotMatrix*
SegmentsLumbar.PelvisSeg.AnatomicalFrameTrunk.ARel';
#else

SegmentsLumbar.PelvisSeg.Axes0=
RotMat((pi/180)*JointPos.PelvisRotZ ,z)* 
RotMat((pi/180)*JointPos.PelvisRotY ,y)*
RotMat((pi/180)*JointPos.PelvisRotX ,x)*
SegmentsLumbar.PelvisSeg.AnatomicalFrameTrunk.ARel';
#endif