Using an axes call could make the axis limits a bit more obvious, and to call attention to a specific point, one option is to draw a straight vertical line to it —
[X,Y,Z] = peaks(20);
F = scatteredInterpolant(X(:),Y(:),Z(:));
Zsel = F(-1, 2)
figure
surf(X,Y,Z, 'FaceAlpha',0.5)
hold on
plot3([1 1]*(-1), [1 1]*2, [min(zlim) Zsel], '-k', 'LineWidth',2)
hold off
grid on
axis('tight')
xlabel('x')
ylabel('y')
view(-120,30)
Adding a text object is also an option.
Experiment to get different results.
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