I have come into a problem recently when trying to rotate 3D objects. I am building a GUI and I have a separate figure where an object is plotted. In the figure, I allow the user to use MATLAB's built-in rotate button to move the object around. However, I am unable to have the light also follow the rotation as it seems to be fixed on one part of the object. To create the light, I am using

```
c=camlight('right');
set(c,'style','infinite');
```

One solution I have thought of is to add light whenever the user releases the rotate button, but this is not very nice. I also do not know how to use the rotate callbacks when the button is in a separate figure.

Does anyone know how to make the light "track" the 3D rotation, so that the current view is illuminated?

Thanks!

Answer:

You can implement an own functionality to adjust the axes and the lights at the same time. This way the light gets adjusted continuously while rotating the axes.

```
function follow_me_1
figure
axes('buttondownfcn', @buttondownfcn); % assign callback
set(gca,'NextPlot','add'); % add next plot to current axis
surf(peaks,'hittest','off'); % hittest -> off is important
view(3); % view to start from
c = camlight('headlight'); % add light
set(c,'style','infinite'); % set style of light
function buttondownfcn(ax,~)
fig = ancestor(ax,'figure'); % get figure handle
[oaz, oel] = view(ax); % get current azimuth and elevation
oloc = get(0,'PointerLocation'); % get starting point
set(fig,'windowbuttonmotionfcn',{@rotationcallback,ax,oloc,oaz,oel});
set(fig,'windowbuttonupfcn',{@donecallback});
end
function rotationcallback(~,~,ax,oloc,oaz,oel)
locend = get(0, 'PointerLocation'); % get mouse location
dx = locend(1) - oloc(1); % calculate difference x
dy = locend(2) - oloc(2); % calculate difference y
factor = 2; % correction mouse -> rotation
newaz = oaz-dx/factor; % calculate new azimuth
newel = oel-dy/factor; % calculate new elevation
view(ax,newaz,newel); % adjust view
c = camlight(c,'headlight'); % adjust light
end
function donecallback(src,~)
fig = ancestor(src,'figure'); % get figure handle
set(fig,'windowbuttonmotionfcn',[]); % unassign windowbuttonmotionfcn
set(fig,'windowbuttonupfcn',[]); % unassign windowbuttonupfcn
end
end
```

`rotate3d`

This example uses the built-in `rotate3d`

and assigned callback functions. This is the 'not very nice'-solution but takes only some lines of code.

```
function follow_me_2
surf(peaks); % Load demo data
c = camlight('headlight'); % Create light
set(c,'style','infinite'); % Set style
h = rotate3d; % Create rotate3d-handle
h.ActionPostCallback = @RotationCallback; % assign callback-function
h.Enable = 'on'; % no need to click the UI-button
% Sub function for callback
function RotationCallback(~,~)
c = camlight(c,'headlight');
end
end
```

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