p = ContourPlot3D[x^2 + y^3 - z^3 == 0, {x, -2, 2}, {y, -2, 2}, {z, -2, 2}, PlotPoints -> Automatic] data = (InputForm@p)[[1, 1, 1]]
and
data = Reap[DensityPlot[Sin[x*y], {x, 0, 2 Pi}, {y, 0, 2 Pi}, EvaluationMonitor :> Sow[{x, y, Sin[x*y]}]]][[2, 1]]; ListPlot3D[data]