x, y, z = var('x, y, z')
from sage.plot.plot3d.parametric_surface import ParametricSurface
def f1(x,z): return x, x^2, z
def f2(x,y): return x, y, 3*y
def f3(x,y): return x, y, y+2
fig1 = ParametricSurface(f1, (srange(-1.5,1.5,0.1), srange(0,3.5,0.1)) ,figsize=[8,8], opacity=0.6)
fig2 = ParametricSurface(f2, (srange(-1.5,1.5,0.1), srange(0,2,0.1)), figsize=[8,8], opacity=0.6)
fig3 = ParametricSurface(f3, (srange(-1.5,1.5,0.1), srange(0,2,0.1)), figsize=[8,8], opacity=0.6)
P = fig1 + fig2 + fig3
show(P)