pcshow permanently changes figure window?

This is a minor issue but I'm not sure it's intended behaviour. When using pcshow to display a pointcloud, the figure window switches to a pointcloud viewer appearance (black background) and this change is persistent through clearing the figure (i.e., with clf).

Simple example:

load('object3d.mat')
figure(1);
pcshow(ptCloud);

clf; %This should leave us with a blank figure. 
A = [0 0 0;0 1 0;0 0 1];
plot3(A(:,1),A(:,2),A(:,3),'.'); %plot something

This behaviour seems inconsistent with most other use cases in which clf completely resets the figure to default.

Answer 1

[Ishan]

clfdeletes all children of the current figure that have visible handles.

load('object3d.mat') 
figure(1); 
pcshow(ptCloud); 

clf; %This should leave us with a blank figure.  
A = [0 0 0;0 1 0;0 0 1]; 
plot3(A(:,1),A(:,2),A(:,3),'.'); %plot something 

So, in your case also the axes get cleared after clf is called (resulting in a black screen) and values get reset to default. When you plot on the same figure it gets plotted over the same initial set of axes you used earlier, hence the behavior seems to be consistent.

For more information, please refer to: -

Clear figure - MATLAB clf - MathWorks India

Also, the recommended function to use for removing app data is actually ‘rmappdata’. ‘clf’ us mainly used to clear the figure window. The syntax for ‘rmappdata’ is as follows:

rmappdata(h,name) % removes the application-defined data, name, from its association with the UI component, h.

Remove application data - MATLAB rmappdata - MathWorks India

[John]

Thanks for your reply and to (Pravarthana) as well. But I still think there's a disconnect between what's happening and what users expect to happen.

I'll accept that as stated in the documentation:

clf (without any modifiers), deletes all children of the current figure that have visible handles

However, there is the extra

clf reset (different syntax) deletes all children of the specified figure and resets its properties.

Interstingly, applied to my previous example, this now gives an error.

load('object3d.mat') 
figure(1); 
pcshow(ptCloud); 

clf reset;

Warning: Error occurred while executing the listener callback for event ObjectBeingDestroyed defined for class matlab.graphics.chart.primitive.Scatter:
Dot indexing is not supported for variables of this type.

Error in pointclouds.internal.pcui.initializePCSceneControl>cleanupPCSceneControl (line 1250)
delete(hui.UIContextMenu);

Error in clo (line 53)
obj.clo(hsave, (do_reset == 1)); % Call clo method on graphics class

Error in clf (line 117)
clo(fig, extra{:});

Error in LiveEditorEvaluationHelperEeditorId (line 4)
clf reset;

Error in connector.internal.fevalMatlab

Error in connector.internal.fevalJSON

I would maintain that based on customary understanding of the intended usage of this function, that this should not give an error.

Answer 2

[Pravarthana P]

Hi John Enright,

The functionality of ‘clf’ command is to clear the contents of the figure window.

For more information the following documentation link can be referred.

To clear the point cloud viewer from the associated UI component using "rmappdata"may be helpful.

‘rmappdata’ will remove the application data, identified by name, from its association with the UI component obj.

The following documentation links may be used for further information:

Clear figure - MATLAB clf (mathworks.com)

Remove application data - MATLAB rmappdata (mathworks.com)

Hope this information helps you!