SeedRandom[35]; data = RandomReal[1, {7, 7, 7}]; f = BSplineFunction[data, 3]; Manipulate[ DensityPlot[f[x, y, z], {x, 0, 1}, {y, 0, 1}, Mesh -> None, ColorFunction -> "SunsetColors"], {z, 0, 1, .1}, SaveDefinitions -> True]