How to find the geometrical information of selected area?

Question

I am new of the MeshLab. I want to find the face indexes (face identifier number ) of the selected area. I used the information function (yellow and ! mark), but it provides vertical information and face number of a point. Is there a method to find the face index numbers (not total face number) of the selected area?

Answer 1

You can see the number of the selected vertices and faces for the current mesh in the lower part of the screen.

Answer 2

There is two approaches for this, depending of the size of your mesh.

If your mesh is small (say less than 150 faces) and your selection is less than 10 faces, you can enable the "render->Show Labels" option menu. This will print the info you need, but clutter the screen if there is a high number of faces there. You can change option to show only indexes for faces and not for vertices.

The second approach is to save a file with the information that you need. To do this, convert your selection into a quality value using the ‘Per Face Quality Function’ filter and using the expression "fsel * fi", which will assign each face a value "face index if selected, 0 if not". After this, export your mesh to a ASCII ply file and select the "save quality" box in the export options.

Open the file with a text editor or custom program and read the values from the last column of lines describing a face. One trick is to use the command grep with the expression "^3 " (which will pass only the lines that define a triangular facet" and -v " 0 $" (which will pass only selected faces"

In this example, our selection were the faces with index number 128, 138, 156, 168, ... 408.