you can get the x y and z data from a fig
%%some figure with data on it
fig = figure(1);
z = 0:10;
x=15:25;
y=10:-1:0;
plot(x,y,z)
%%grab data
linehandle = findall(gca,'type','line')
linehandle=linehandle(1)%use the first line if there is more then 1
xfig=get(linehandle,'XData')
yfig=get(linehandle,'YData')
zfig =get(linehandle,'ZData')
all(x==xfig)&all(y==yfig)&all(z==zfig)% check if the data is the same
from here you can do your interp3
