59 def hessSDF(x, y, z, t):
61 df2_dx2 = (WavySurface.sDF(x + delta, y,z,t) - 2 * WavySurface.sDF(x, y,z,t) + WavySurface.sDF(x - delta, y,z, t)) / (delta ** 2)
62 df2_dy2 = (WavySurface.sDF(x, y + delta,z,t) - 2 * WavySurface.sDF(x, y,z,t) + WavySurface.sDF(x, y - delta,z, t)) / (delta ** 2)
63 df2_dxdy = (WavySurface.sDF(x + delta, y + delta,z,t) - WavySurface.sDF(x + delta, y - delta, z, t) - WavySurface.sDF(x - delta, y + delta,z, t) + WavySurface.sDF(x - delta, y - delta,z,t)) / (4 * delta ** 2)
65 return np.hstack([df2_dx2.reshape((-1,1)), df2_dxdy.reshape((-1,1)), np.zeros_like(df2_dy2).reshape((-1,1)),df2_dy2.reshape((-1,1)), np.zeros_like(df2_dy2).reshape((-1,1)), np.zeros_like(df2_dy2).reshape((-1,1))])