For the following plots, colormap I have tried does not seem to be working.

Hello,
I am trying to make a vector field plot using arrow3D. Here, I want the colormap on arrow to change with the variation in z-axis more like aplot of a magnetic skyrmion field. But the cmap is not wokring.
kindly don't post the entire code. A snippet of code for the understanding would be a great help!

Thanks.

[Adam Danz]

arrow3D is not at MATLAB function. Perhaps the author of the code found it on the file exchange.

[KM]

Yes @Adam Danz. I have used it from file exchange.. The package seems to be woking fine for my other plots so I used it insead of quiver3D here.

The problem though here, is the code implementation that I'm not able to rectify.

A great help would be if you can cross check the code?

Thanks.

[KM]

Alternatively, I have used quiver3 but I don't know how to add the colormap for quivers or even if it is possible to do so. Below is the working code with quiver3.

[Image Analyst]

Reconcile "colormap I have tried does seem to be working" with "the cmap is not wokring". Is it working or not, or sometimes working and sometimes not working?

[KM]

Hi, @Image Analyst

V sorry. There was a typo in the caption. colormap I have tried does not* seem to be working.

Although I use an older version of MATLAB but did run it on MATLAB online with the latest version available. It is not working there as well.

Answer 1

[Adam Danz]

The question is about cmap but cmap doesn't exist in you code so I assume cmap is a variable (or function) in arrow3D but I don't know what arrow3D is so how is it possible to address the issue?

You're right that MATLAB's quiver3 does not support colormap mapping. You could plot each quiver arrow individually in which case each arrow could have its own color but depending on the number of arrows, this could make take up a lot of memory since you're creating many quiver objects that way. That method is demonstrated in the two answers below (in 2D).

• https://www.mathworks.com/matlabcentral/answers/598141-how-do-i-create-a-colour-quiver-plot-colquiver-on-top-of-a-pcolor-depth-map#answer_498724
• https://www.mathworks.com/matlabcentral/answers/828465-quiver-with-color-add-on#answer_698630

Maybe there's a 3D demo in the forum, I haven't checked.

[KM]

Thank you for your response @Adam Danz

I have seen few plots in the same catagory with arrow3D in few papers specifically entioned the method.

I'm able to colormap around the periphery but it's just not wokring in radial as as i'm moving from center to periphery and arrow angle varying with z axis.

my colormap code in the code is here:

 % Normalize the z-direction value between 0 and 1
            min_z = min(deltaV0(3));
            max_z = max(deltaV0(3));
            if deltaV(3) <= min_z
                z_norm = 0;
            elseif deltaV(3) >= max_z
                z_norm = 1;
            else
                z_norm = (deltaV(3) - min_z) / (max_z - min_z);
            end

% Get the color from the colormap based on the normalized z-direction value
colorCode = colormap(jet(64));
arrowColor = colorCode(round(z_norm * 63)+1, :);

I normalised and assigned the colormap to the arrow. Here something seems to be not wokring properly. I'm not able to catch it.

[Adam Danz]

> Here something seems to be not wokring properly

Are you getting an error message or is there something about color that is unexpected?

[KM]

Nope! No error.

[Adam Danz]

We don't have enough information to help. Specifically, we don't know what it means that something is not working property. We don't know how it's working, how it's supposed to work, and we don't know what it is.

[KM]

@Adam Danz

(we don't know what it is) I'm trying to plot a skyrmion texture and above attatched code is what I tried.

For colormap of the arrows, I have used the above commented code (you asked where) which is not wokring the way I intent it to work for example as like a skyrmion image.

(how it's supposed to work). To me, the my code implementation in colorcoding section is not correct (something is not working property) although i'm getting any error.

Please let me know if I missed any details?

[Adam Danz]

> ...is not wokring the way I intent it to work...

Thanks for the skyrmion image, but it's still not clear what the problem is. We don't have enough information about the code, what it's supposed to do, and what it's currently doing.

[KM]

@Adam Danz

The implemented code for the colourmap the arrows is not that of a skyrmion. And I want a skyrmion colormap there.

I seek suggestions to make it right i.e of a skyrmion. I don't know where have I made the mistake that I'm getting a wrong colormap. So if there are any mistakes, would appreciate being poined out.

I have attatched the code here again Furthermore, if it still lacks the problem understanding, I will suggest to run the code.

[Adam Danz]

I ran the code and get the error "Unrecognized function or variable 'arrow3D'.". Thus, I cannot produce the image produced by arrow3D.

I can see that your code converts the data to polar coordinates and then applies some rotation matricies to transform the data, then it's normalized and plotted with arrow3D. I also did a google image search for skyrmion to get a sense of what that should look like. The parts I'm still missing are how your visualization differs from skyrmion (I can't see your visualization because I don't have arrow3D) and how the inputs to arrow3D are used.

[Adam Danz]

Here's an annology,

Why is the ouput (z) 5?

x = 1; 
y = 2; 
z = myFunction(x,y);
z = 
    5

[KM]

@Adam Danz That's because you have not installed file exchange arrow3D package* (updated the link). https://in.mathworks.com/matlabcentral/fileexchange/12274-3d-arrow-with-many-color-parameter-options?s_tid=srchtitle

Attached is my plot. I have also attatched the package files here in case you want to run with arrow3D.