clf,x=[-8:0.2:8];y=x;[X,Y]=meshgrid(x,y);ZZ=X.^2-Y.^2;
ii=find(abs(X)>6|abs(Y)>6);	%確定超出[-6,6]范圍的格點下標
ZZ(ii)=zeros(size(ii));			%強制為0
surf(X,Y,ZZ),shading interp;colormap(copper)
light('position',[0,-15,1]);lighting phong
material([0.8,0.8,0.5,10,0.5])