function [w,dwdx,dwdy] = cubwgt(dif,t,v,dmax,dm)
% CUBIC SPLINE WEIGHT FUNCTION
l = length(v);
for i=1:l
drdx = sign(dif(1,i))/dm(1,v(i));
drdy = sign(dif(2,i))/dm(2,v(i));
rx = abs(dif(1,i))/dm(1,v(i));
ry = abs(dif(2,i))/dm(2,v(i));
if rx>0.5
wx = (4/3)-4*rx+4*rx*rx -(4/3)*rx^3;
dwx = (-4 + 8*rx-4*rx^2)*drdx;
elseif rx<=0.5
wx = (2/3) - 4*rx*rx + 4*rx^3;
dwx = (-8*rx + 12*rx^2)*drdx;
end
if ry>0.5
wy = (4/3)-4*ry+4*ry*ry -(4/3)*ry^3;
dwy = (-4 + 8*ry-4*ry^2)*drdy;
elseif ry<=0.5
wy = (2/3) - 4*ry*ry + 4*ry^3;
dwy = (-8*ry + 12*ry^2)*drdy;
end
w(i) = wx*wy;
dwdx(i) = wy*dwx;
dwdy(i) = wx*dwy;
end