load(draw);

Código utilizado para generar los ejemplos de las transparencias

EXTREMOS. EJEMPLO:

wxdraw3d(contour_levels = 15, 
            contour = both, surface_hide=true,
            explicit((2-sin(y^2)+x^2)*exp(1-x^2-(y^2/4)*cos(x)),x,-3,2,y,-3,2));

PUNTO DE SILLA. EJEMPLO:

wxdraw3d(explicit(y^2-x^2,x,-2,2,y,-2,2),
            color = "red",
            grid = true,
            point_type = filled_circle,
            key = "Punto de silla",
            point_size = 2,
            points([[0,0,0]]));

Ejemplo de las transparencias: extremos relativos y absolutos

f(x,y):=x*y*(1-x^2-y^2);

draw3d(enhanced3d=false,
             contour_levels = 15,
             contour = both,
             proportional_axes=xyz,
             explicit(f(x,y),x,-1.1,1.1,y,-1.1,1.1),
             point_type = filled_circle,
             color="blue",
             key = "Puntos de silla",
             point_size = 2,
             points([[0,0,f(0,0)],
                         [0,1,f(0,1)],
                         [0,-1,f(0,-1)],
                         [-1,0,f(-1, 0)],
                         [1,0,f(1,0)]]),
             color="red",
             key="Maximos",
             point_size=2,
             points([[0.5,0.5,f(0.5,0.5)],
                        [-0.5,-0.5,f(-0.5,-0.5)]]),
             color="green",
             key="Minimos",
             point_size=2,
             points([[-0.5,0.5,f(-0.5,0.5)],
                        [0.5,-0.5,f(0.5,-0.5)]]));