39 lines (30 with data), 771 Bytes

AnyVar VectorLength = 0.005;
AnyVar VectorThickness = 0.0035;


AnyVector MuscleForceDir = {.Org.r[0],.Org.r[1],.Org.r[2]}-{.Ins.r[0],.Ins.r[1],.Ins.r[2]};

AnyVector MuscleForceDirUnit = MuscleForceDir/vnorm(MuscleForceDir);


AnyDrawVector DrawOrg = 
{
  Vec = .MuscleForceDirUnit*..Ft*(-1)*.VectorLength;
  //PointAway = On;
  GlobalCoord = On;
  Line = 
  {
  Style = Line3DStyleFull;
  Thickness = ..VectorThickness;
  RGB = {1, 0, 0};
  };
  AnyRefFrame &Origin = ..Org;
};


AnyDrawVector DrawIns = 
{
  Vec = .MuscleForceDirUnit*..Ft*.VectorLength;
  //PointAway = On;
  GlobalCoord = On;
  Line = 
  {
  Style = Line3DStyleFull;
  Thickness = ..VectorThickness;
  RGB = {1, 0, 0};
  };
  AnyRefFrame &Insertion = ..Ins;
};