Matlab patch: fix the colorscale for a video

Hey everyone,

I am blocked with 'patch' function in Matlab for some time. Any help will be strongly appreciated.

So I am using the 'patch' function to plot numerical results at different time steps, based on a triangle mesh. If I use the function below:

h = patch('Faces',m.IKLE, 'Vertices', m.XYZ,'FaceVertexCData',m.RESULT(:,3), 'Facecolor', 'interp','EdgeColor','black','linewidth',0.01 );

where 'm' is a structural object that I have created; inside it includes faces and vertices information, also the data that I would like to plot, here shows m.Result(:,3), meaning the result at time step 3. However, if I want to plot all results of different time steps in order to create a video, the Matlab function will call this at each time step. The problem is, the colorscale keeps changing. For example, at time 1, the value ranges from 1 to 2, then 1 may be red, and 2 may be green. But at time 2, the value may range from 1 to 10, then at this time, 10 is green. I would like to write a small program, to detect the largest and smallest value that can ever occur, then fix a colormap to this range. Does anyone have any idea about how to fix the mapping step? Say, I want to fix, 1 to red, 10 to green, the middile values and colors to be interpolated. Then this colorscale will be used for each time step.

Thank you very much and hope you have a good day!

Qinghui

Answer 1

[Walter Roberson]

Set the patch CDataMapping property to 'direct'. The FaceVertexCData value will then be used as an index into the colormap.

You could construct a custom colormap with 10 entries, one for each of the values you want to define. If that does not give you a high enough resolution, you could multiply the input m.RESULT(:,3) by N/10 where N is the number of colors in your color map .

Alternately, you can continue to use the default CDataMapping of 'scaled' and use caxis([1 10])

[zhang qinghui]

That's very kind of you! Thank you very much and I am going to try!

Greetings,

Have a good day!

Qinghui