function obj = updateBar3(obj, surfaceIndex)

%-AXIS INDEX-%
axIndex = obj.getAxisIndex(obj.State.Plot(surfaceIndex).AssociatedAxis);

%-CHECK FOR MULTIPLE AXES-%
[xsource, ysource] = findSourceAxis(obj,axIndex);

%-SURFACE DATA STRUCTURE- %
bar_data = get(obj.State.Plot(surfaceIndex).Handle);
figure_data = get(obj.State.Figure.Handle);

%-AXIS STRUCTURE-%
axis_data = get(ancestor(bar_data.Parent,'axes'));

%-GET SCENE-%
eval(['scene = obj.layout.scene' num2str(xsource) ';']);

%-------------------------------------------------------------------------%

%-associate scene-%
obj.data{surfaceIndex}.scene = sprintf('scene%d', xsource);
    
%-------------------------------------------------------------------------%

%-surface type-%
obj.data{surfaceIndex}.type = 'mesh3d';

%-------------------------------------------------------------------------%
    
%-FORMAT DATA-%
xdata = bar_data.XData;
ydata = bar_data.YData;
zdata = bar_data.ZData;
cdata = bar_data.CData;

%-parse xedges-%
xedges = xdata(2, 1:2:end);

%-parse yedges-%
yedges = ydata(2:6:end, 2);
yedges = [yedges', mean(diff(yedges(1:2)))];

%-parse values-%
values = [];
for n = 1:6:size(zdata, 1)
    values = [values, diff(zdata(n:n+1, 2))];
end

%-parse offsets-%
offsets = zdata(1:6:end, 2)';
    
%-------------------------------------------------------------------------%

%-get the values to use plotly's mesh3D-%
bargap = diff(yedges(1:2)) - diff(ydata(2:3));
[X, Y, Z, I, J, K] = get_plotly_mesh3d(xedges, yedges, values, bargap);

%---------------------------------------------------------------------%

%-reformat Z according to offsets-%
m = 1;
lz2 = 0.5*length(Z);

for n = 1:4:lz2
    Z(n:n+3) = Z(n:n+3)+offsets(m);
    Z(n+lz2:n+lz2+3) = Z(n+lz2:n+lz2+3)+offsets(m);
    m = m + 1;
end

%-------------------------------------------------------------------------%

%-set mesh3d data-%
obj.data{surfaceIndex}.x = X;
obj.data{surfaceIndex}.y = Y;
obj.data{surfaceIndex}.z = Z;
obj.data{surfaceIndex}.i = int16(I-1);
obj.data{surfaceIndex}.j = int16(J-1);
obj.data{surfaceIndex}.k = int16(K-1);

%-------------------------------------------------------------------------%

%-coloring-%
cmap = figure_data.Colormap;

if isnumeric(bar_data.FaceColor)
    
    %-paper_bgcolor-%
    col = 255*bar_data.FaceColor;
    col = sprintf('rgb(%f,%f,%f)', col);
    
else
    switch bar_data.FaceColor
        
        case 'none'
            col = 'rgba(0,0,0,0)';
            
        case {'flat','interp'}
            
            switch bar_data.CDataMapping
                
                case 'scaled'
                    capCD = max(min(cdata(1,1),axis_data.CLim(2)),axis_data.CLim(1));
                    scalefactor = (capCD - axis_data.CLim(1))/diff(axis_data.CLim);
                    col =  255*(cmap(1+ floor(scalefactor*(length(cmap)-1)),:));
                case 'direct'
                    col =  255*(cmap(cdata(1,1),:));
                    
            end
            
            col = sprintf('rgb(%f,%f,%f)', col);

        case 'auto'
            col = 'rgb(0,113.985,188.955)';
    end
end

obj.data{surfaceIndex}.color = col;

%-------------------------------------------------------------------------%

%-some settings-%
obj.data{surfaceIndex}.contour.show = true;
obj.data{surfaceIndex}.contour.width = 6;
obj.data{surfaceIndex}.contour.color='rgb(0,0,0)';
obj.data{surfaceIndex}.flatshading = false;

%-------------------------------------------------------------------------%

%-lighting settings-%
obj.data{surfaceIndex}.lighting.diffuse = 0.8;
obj.data{surfaceIndex}.lighting.ambient = 0.65;
obj.data{surfaceIndex}.lighting.specular = 1.42;
obj.data{surfaceIndex}.lighting.roughness = 0.52;
obj.data{surfaceIndex}.lighting.fresnel = 0.2;
obj.data{surfaceIndex}.lighting.vertexnormalsepsilon = 1e-12;
obj.data{surfaceIndex}.lighting.facenormalsepsilon = 1e-6;

obj.data{surfaceIndex}.lightposition.x = 0;
obj.data{surfaceIndex}.lightposition.y = 0;
obj.data{surfaceIndex}.lightposition.z = 0;

%-------------------------------------------------------------------------%

%-surface name-%
obj.data{surfaceIndex}.name = bar_data.DisplayName;

%-------------------------------------------------------------------------%

%-surface visible-%
obj.data{surfaceIndex}.visible = strcmp(bar_data.Visible,'on');

%-------------------------------------------------------------------------%

leg = get(bar_data.Annotation);
legInfo = get(leg.LegendInformation);

switch legInfo.IconDisplayStyle
    case 'on'
        showleg = true;
    case 'off'
        showleg = false;
end

obj.data{surfaceIndex}.showlegend = showleg;

%-------------------------------------------------------------------------%

%-SETTING SCENE-%

%-------------------------------------------------------------------------%

%-aspect ratio-%
ar = obj.PlotOptions.AspectRatio;

if ~isempty(ar)
    if ischar(ar)
        scene.aspectmode = ar;
    elseif isvector(ar) && length(ar) == 3
        xar = ar(1);
        yar = ar(2);
        zar = ar(3);
    end
else

    %-define as default-%
    xar = max(xedges(:));
    yar = max(yedges(:));
    zar = 0.7*max([xar, yar]);
end

scene.aspectratio.x = xar;
scene.aspectratio.y = yar;
scene.aspectratio.z = zar;

%-------------------------------------------------------------------------%

%-camera eye-%
ey = obj.PlotOptions.CameraEye;

if ~isempty(ey)
    if isvector(ey) && length(ey) == 3
        scene.camera.eye.x = ey(1);
        scene.camera.eye.y = ey(2);
        scene.camera.eye.z = ey(3);
    end
else

    %-define as default-%
    scene.camera.eye.x = xar + 7; 
    scene.camera.eye.y = yar - 2;
    scene.camera.eye.z = zar + 0.5;
end

%-------------------------------------------------------------------------%

%-axis configuration-%
scene.xaxis.range = axis_data.XLim(end:-1:1);
scene.yaxis.range = axis_data.YLim;
scene.zaxis.range = axis_data.ZLim;

scene.xaxis.tickvals = axis_data.XTick;
scene.xaxis.ticktext = axis_data.XTickLabel;

scene.yaxis.tickvals = axis_data.YTick;
scene.yaxis.ticktext = axis_data.YTickLabel;

scene.zaxis.tickvals = axis_data.ZTick;
scene.zaxis.ticktext = axis_data.ZTickLabel;

scene.xaxis.zeroline = false;
scene.yaxis.zeroline = false;
scene.zaxis.zeroline = false;

scene.xaxis.showline = true;
scene.yaxis.showline = true;
scene.zaxis.showline = true;

scene.xaxis.tickcolor = 'rgba(0,0,0,1)';
scene.yaxis.tickcolor = 'rgba(0,0,0,1)';
scene.zaxis.tickcolor = 'rgba(0,0,0,1)';

scene.xaxis.ticklabelposition = 'outside';
scene.yaxis.ticklabelposition = 'outside';
scene.zaxis.ticklabelposition = 'outside';

scene.xaxis.title = axis_data.XLabel.String;
scene.yaxis.title = axis_data.YLabel.String;
scene.zaxis.title = axis_data.ZLabel.String;

%-------------------------------------------------------------------------%

%-SET SCENE TO LAYOUT-%
obj.layout = setfield(obj.layout, sprintf('scene%d', xsource), scene);

%-------------------------------------------------------------------------%

end

function bar_ = bar_data(position3d, size_)
    % position3d - 3-list or array of shape (3,) that represents the point of coords (x, y, 0), where a bar is placed
    % size = a 3-tuple whose elements are used to scale a unit cube to get a paralelipipedic bar
    % returns - an array of shape(8,3) representing the 8 vertices of  a bar at position3d

    if nargin < 2
        size_ = [1, 1, 1];
    end

    bar_ = [...
            0, 0, 0; ...
            1, 0, 0; ...
            1, 1, 0; ...
            0, 1, 0; ...
            0, 0, 1; ...
            1, 0, 1; ...
            1, 1, 1; ...
            0, 1, 1 ...
            ]; % the vertices of the unit cube

    for n =1:size(bar_, 1)
        bar_(n,:) = bar_(n,:) .* size_; % scale the cube to get the vertices of a parallelipipedic bar_
    end


    bar_ = bar_ + position3d; %translate each  bar_ on the directio OP, with P=position3d
end

function [vertices, I, J, K] = triangulate_bar_faces(positions, sizes)
    % positions - array of shape (N, 3) that contains all positions in the plane z=0, where a histogram bar is placed 
    % sizes -  array of shape (N,3); each row represents the sizes to scale a unit cube to get a bar
    % returns the array of unique vertices, and the lists i, j, k to be used in instantiating the go.Mesh3d class

    if nargin < 2
        sizes = ones(size(positions,1), 3); %[(1,1,1)]*len(positions)
    else
        sizes;
        % if isinstance(sizes, (list, np.ndarray)) and len(sizes) != len(positions):
        %     raise ValueError('Your positions and sizes lists/arrays do not have the same length')
    end

    c = 1;
    for n = 1:size(positions, 1)
        if sizes(n, 3) ~= 0
            all_bars(:,:,c) = bar_data(positions(n,:), sizes(n,:))';
            c = c+1;
        end
    end

    % all_bars = [bar_data(pos, size)  for pos, size in zip(positions, sizes) if size[2]!=0]
    [r, q, p] = size(all_bars);

    % extract unique vertices from the list of all bar vertices
    all_bars = reshape(all_bars, [r, p*q])';
    [vertices, ~, ixr] = unique(all_bars, 'rows');

    %for each bar, derive the sublists of indices i, j, k assocated to its chosen  triangulation
    I = [];
    J = [];
    K = [];

    for k = 0:p-1
        aux = ixr([1+8*k, 1+8*k+2,1+8*k, 1+8*k+5,1+8*k, 1+8*k+7, 1+8*k+5, 1+8*k+2, 1+8*k+3, 1+8*k+6, 1+8*k+7, 1+8*k+5]);
        I = [ I;  aux(:)];
        aux = ixr([1+8*k+1, 1+8*k+3, 1+8*k+4, 1+8*k+1, 1+8*k+3, 1+8*k+4, 1+8*k+1, 1+8*k+6, 1+8*k+7, 1+8*k+2, 1+8*k+4, 1+8*k+6]);
        J = [ J;  aux(:)];
        aux = ixr([1+8*k+2, 1+8*k, 1+8*k+5, 1+8*k, 1+8*k+7, 1+8*k, 1+8*k+2, 1+8*k+5, 1+8*k+6, 1+8*k+3, 1+8*k+5, 1+8*k+7]);
        K = [ K;  aux(:)];
    end

end

function [X, Y, Z, I, J, K] = get_plotly_mesh3d(xedges, yedges, values, bargap)
    % x, y- array-like of shape (n,), defining the x, and y-ccordinates of data set for which we plot a 3d hist

    xsize = xedges(2)-xedges(1)-bargap;
    ysize = yedges(2)-yedges(1)-bargap;
    [xe, ye]= meshgrid(xedges(1:end-1), yedges(1:end-1));
    ze = zeros(size(xe));

    positions = zeros([size(xe), 3]);
    positions(:,:,1) = xe;
    positions(:,:,2) = ye;
    positions(:,:,3) = ze;

    [m, n, p] = size(positions);
    positions = reshape(positions, [m*n, p]);

    h = values'; h = h(:);
    sizes = [];
    for n = 1:length(h)
        sizes = [sizes; ysize, ysize, h(n)];
    end

    [vertices, I, J, K]  = triangulate_bar_faces(positions, sizes);
    X = vertices(:,1);
    Y = vertices(:,2);
    Z = vertices(:,3);

end
