function r = vp( x1,x2,z2,y1,y2,m_ele,dz,hmax)
r=zeros(1,m_ele);
for i=1:1:m_ele
    z1=i*dz;
    if y1+z1<=hmax
        r(i)=hypot((y1+z1)-(y2+z2),x2-x1);
    end
end

