Position hogehoge(Position pos1, Position pos2, ushort val)
{
double px, py, pz;
duoble tx, ty, tz;

double len;
Position ret;

px=pos1.x;
py=pos1.y;
pz=pos1.z;

tx=pos2.x;
ty=pos2.y;
tz=pos2.z;

len = sqrt( pow((px - tx),2) + pow((py - ty),2) + pow((pz - ty),2) );

ret.x = ((tx-px)/len)*val;
ret.y = ((ty-py)/len)*val;
ret.z = ((tz-pz)/len)*val;

return( ret );
}