xs = [1 3 5 7];
ys = [1 3 5];
zs = [1 3];
vs(1:3, 1:4, 1) = 1;
vs(1:3, 1:4, 2) = 3;

[X Y Z] = meshgrid(xs, ys, zs);

% some stuff to test
testx = [2 4 6];
testy = [2 4];
testz = [2];

[Xi Yi Zi] = meshgrid(testx, testy, testz);

result = interp3(X, Y, Z, vs, Xi, Yi, Zi)