I do not have the function you used to create the surface in your Question.
Try this with it:
[X,Y] = ndgrid(-2.5:0.1:2.5); % Independent Variable Grid
Z = sin(X).^2 + cos(Y); % Dependent Variable (Use Your Function)
x_room = 1; % X-Room Coordinate
y_room = -1; % Y-Room Coordinate
z_room = griddata(X,Y,Z, x_room, y_room); % Interpolated Z-Room Coordinate
figure
surfc(X, Y, Z)
hold on
plot3(x_room, y_room, z_room, 'rd', 'MarkerFaceColor','r', 'MarkerSize',10)
hold off
grid on
Substitute your function for mine, and choose whatever you want for the coordinates (providing they are within the specified x and y limits).
