Retrieve 3D location from clicked pixel / datatip position

Question

Roger Breton 2022-2-23

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回答： Roger Breton 2022-2-24

Affiche_Lab_ReshapePermute_2022_02_22.m

I attached a copy of my code (I did not includes the images). My question is how would I retrieve the CIE Lab color coordinates pointed to by the mouse and the datatip on the 3D graph? Not sure which function to use best? I guess I have to setup a mouseclick callback function but I don't know whether I can access the datatip properties from that function? This screen capture shows what I'm trying to do :

On the right is the RGB image displayed in its own figure and the left is the 'loRes' corresponding data, in CIE Lab. When I click on an the existing points, in the scatter3 graph, with the mouse, I get a DataTip "baloon" showing the CIE Lab value pointed to by the mouse. Those are the values that I'm trying to retrieve and use as an index on the right figure, to be able to show the xy location with a marker? All I'm trying to accomplish is to allow students to select a point in the 3D space on the left and show them what the corresponding RGB color is.

I have tons of ideas but far too little Matlab knowledge...

Any help is appreciated.

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Roger Breton 2022-2-23

I execute my code with the new function callback and placed a breakpoint inside to be able to peek at the data, and this is what I get when I place the mouse on the eventData :

Is it the IntersectionPoint I'm after? I can see the [38 -81 27] vector makes total sens as it would represent an estimate of the CIE Lab 3D coordinates, which are b=38 a= -78 and L= 24 according to the datatip capture :

It's a good approximation and I'm sure I would not be too far off the real 3D location. But would there be a way to workaround the scatter 'default' behavior? You see, when the scatter initially displays, there is datatip, somewhere (is it the last point in the XYZ array?) that automatically comes up. I don't know how to disable that behavior (I already asked the question here, in the past, but did not get any direct reply). At any rate, what follows is that, 1) I click once on the round black 'dot', and as soon I do that, the datatip disappears? Then 2) I click a second time on what I think is the same round black dot, to trigger the ButtonDownFn callback. Then 3) I am taken to the callback function in the code, and all I see I have access to are what I captured above in the first yellow image. I still wonder whether it's possible to access the last state -- I guess -- of the Datatip? So that I get as close as possible to an exact match of an exiting 3D point.

Roger Breton 2022-2-23

How about responding to a right-mouse button click?

I'll look around...

Roger Breton 2022-2-23

My latest 'attempt' involves this code :

DataCursorMode1 = datacursormode(fig_3D);

set(DataCursorMode1,'Enable','on','UpdateFcn',@displayCoordinates)

end

function txt = displayCoordinates(~, info)

txt = {sprintf('CIE L: %.0f', info.Position(3)), sprintf('CIE a: %.0f', info.Position(1)), sprintf('CIE b: %.0f', info.Position(2))};

end

At least, using this 'solution', I'm in control of the order in which the values are displayed in the datatip :

Trouble is that, now, I lose all 'default' interactivity : no more Rotate3D functionality until I click on the Rotate3D button, and then I'm automatically "out" of the datacursor mode? I have to alternate between the 'interaction mode' and 'datacursor mode', it's not possible to have the two modes simultaneously active. I understand "why", this is so. Yes, I noticed that, when the mouse hovers empty areas of the graph, that the cursor turns back into a normal mouse pointer?

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Answer 1

Roger Breton 2022-2-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1656960-retrieve-3d-location-from-clicked-pixel-datatip-position#answer_903885

Not a "perfect" answer but I think it's 'workable'.

First, I added a pusbutton to the figure. Then I use this code, to obtain the display coordinates :

DataCursorMode1 = datacursormode(fig_3D);

set(DataCursorMode1,'Enable','on','UpdateFcn',@displayCoordinates)

Then in the callback function, I use this code :

function txt = displayCoordinates(~, info)

global clickedCIE_L clickedCIE_a clickedCIE_b;

clickedCIE_L = info.Position(3);

clickedCIE_a = info.Position(1);

clickedCIE_b = info.Position(2);

txt = {sprintf('CIE L: %.0f', info.Position(3)), sprintf('CIE a: %.0f', info.Position(1)), sprintf('CIE b: %.0f', info.Position(2))};

end

I know, "global variables"... but, have a heart. My projects will never be used for rocket launching...

This solution is not ideal but, as it stands, there is no way, with my level of (ahem!) Matlab 'mastery' to be able to intercept the datatips value when clicked with the mouse otherwise.

And I have to accept that I cannot be simultaneously in both datacursor mode and rotate3D mode. So it's a pain but, I'm satisfied that this is workable.

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