Customize data cursor for 3D objects

Question

Let's say, I have many spheres drawn with surf/mesh function in MATLAB.

I want to display customize data values rather than x,y,z. All values will be different for different spheres and clicking on any point on a particular sphere should display the same data. Refer figure. How do I achieve it?

So far, I'm thinking of using Surface property 'tag' to assign unique string to each sphere. Is there any better way to do it?

[x,y,z] = sphere;
a=[3 1 3 1];
s1=surf(x*a(1,4)+a(1,1),y*a(1,4)+a(1,2),z*a(1,4)+a(1,3),...
        'FaceColor', [1 0 0],'FaceLighting','flat','EdgeColor','none');
s1.Tag = '1';

How should I proceed with custom datacursor function for custom functionality ?

https://www.mathworks.com/help/matlab/ref/matlab.graphics.shape.internal.datacursormanager.html;jsessionid=b5c04ad9f8c193ce76f0df766b7d — Shannon, Jun 22 '20 at 09:31

score 2 · Accepted Answer · answered Jun 22 '20 at 08:54

The datacursor function is an attribute of the figure, so the trick is to assign the datatip update function to the figure.

Placing the custom information for each sphere/graphic object in its Tag property is a good idea for what you want to achieve.

Let's define the update function first. Save the following file under datatip_sphere.m and make sure it is visible in the Matlab path:

function output_txt = datatip_sphere(~,event_obj)
% Display the tag of the cursor target
% obj          Currently not used (empty)
% event_obj    Handle to event object
% output_txt   Data cursor text string (string or cell array of strings).

output_txt = { event_obj.Target.Tag };

Armed with that, now let's draw two spheres and make sure the cursor function displays what you want:

% retrieve the handle of the figure used for sphere display
% (better than calling 'gca' in datacursormode(hfig)
hfig = figure ;

% Draw your objects
[x,y,z] = sphere;
a=[3 1 3 1] ;
b=[5 6 4 1] ;
s1 = surf(x*a(1,4)+a(1,1),y*a(1,4)+a(1,2),z*a(1,4)+a(1,3),...
        'FaceColor', [1 0 0],'FaceLighting','flat','EdgeColor','none','Facealpha',0.5);
hold on 
s2 = surf(x*b(1,4)+b(1,1),y*b(1,4)+b(1,2),z*b(1,4)+b(1,3),...
        'FaceColor', [0 0 1],'FaceLighting','flat','EdgeColor','none','Facealpha',0.5);
axis equal
    
% Add a tag to each object
s1.Tag = 'This is sphere 1';
s2.Tag = 'This is sphere 2';

% Now force the figure datatip function to your custom version
dcm = datacursormode(hfig) ;
dcm.UpdateFcn = @datatip_sphere ;

Obviously, the important lines are the last 4 lines, where you assign a Tag for each of your graphic object, and specially the last two lines where you assign your custom cursor update function to the figure.

Cool, now your datatip will always display the name/tag assigned to the object, regardless of their position:

Customize data cursor for 3D objects

1 Answers1