clear;

deff("[z] = f(x, y)", "z = 0.1*cos(2*%pi*x*5 + %pi/2)");
deff("[z] = g(x, y)", "z = 0.1*cos(2*%pi*x*5)");

function  [X1, Y1, Z1, X2, Y2, Z2] = generation(t, f, g)
taille = size(t, "*");
X1 = ones(taille,1)*t;
Y1 = X1';
Y2 = X1;
Z2 = 0.1 - Y1;

Z1 = f(X1, Y1);
for i = 1:taille
    for j = 1:taille
        if X1(i, j) <= (0.1 + 0.1*cos(2*%pi*Y1(i, j)*5))...
            then Z1(i, j) = %nan;
        end
    end
end

X2 = g(X1, Y1) + 0.1;

for i = 1:taille
    for j = 1:taille
        if Z2(i, j) >= -0.1*sin(2*%pi*X2(i, j)*5)...
            then Z2(i, j) = %nan;
        end
    end
end
endfunction

// ***********************
// * Programme principal *
// ***********************

// ** Tracé des surfaces en nuances de gris

t = 0:3e-3:1;

[x, y, z, xx, yy, zz] = generation(t, f, g);

clf;

surf(x, y, z)
h1 = gce();
h1.thickness = 0;

surf(xx, yy, zz)
h2 = gce();
h2.thickness = 0;

cmap = 0.8*graycolormap(32) + 0.2;
xset("colormap", cmap)

// ** tracé des génératrices

t = 0:2e-2:1;

[x, y, z, xx, yy, zz] = generation(t, f, g);

param3d1(x, y, z)

param3d1(xx, yy, zz)

// ** tracé de l'arête
 
y = 0:3e-3:1;
x = g(y, zeros(y))+0.1;
z = f(x, zeros(y));
param3d1(x, y, z, theta = 190, alpha = 30)
e = gce();
e.thickness = 3;