Identify surfaces of geometry that is imported as stl file to matlab

My code reads an stl file of a geometry on matlab and uses the triangulated elements to determine the angle between the surface normal of each elemnt and a user defined velocity vector.

Now I wish to alter the velocity vector only on certain surfaces of the geometry and not just the elements. I don't intend to manually identify the element ID that form the required surface because the element ID changes with every new stl file that is used in the code.

How do I target the surfaces of the geometry when the stl file stores only vertices and connectivity list of the geometry. Or Is there any other file format which identifies different surfaces that form the geometry.

[dileesh pv]

What is your criteria for selecting surfaces?? I assume, the selected surface will be a collection of elements. If there is a criteria for the surface which can be constructed based on the available data (coordinates, connectivity and normal) or could annotate certain element set, it could be possible.

I feel you can use the 'normal' to the element as a criteria to identify the required surface.

Answer 1

[dileesh pv]

Please check the tool given in the below link. I think it has the provision to select the surfaces.

STL tool - CAD STL