Match matrix values with mesh nodes

I've obtained mesh on an image, and I have a color intensity matrix of the same image. Matrix values I want to multiply with Modulus of Elasticity value and then match them with the numbers of mesh nodes/elements according to their position, and import the result into ANSYS. The matrix and the mesh are attached below.

Mesh is obtained using im2mesh by JieXian Ma. It's represented as a n-by-2 array of nodes (x and y positions), m-by-3 array of triangles (positions of 3 nodes forming a triangle) and m-by-1 array of grayscale phases (phases are initially selected to generate a mesh according to an intensity of gray color)

As I understand, there should be a loop which:

• checks the position of a mesh node (x and y)
• checks the position of a value in the matrix (row and column)
• assigns the value of a matrix to the node (a new array with these values)

Or does the same, but with an element instead of a node (with averaged coordinate between nodes)

But I may be wrong, as I'm new in Matlab

And I don't know how to make this loop properly, because the matrix is a square with many values equal to 0 (it initially was 255 and represented air, I just inversed the values so the air is represented as pure black color), while mesh is made differently and doesn't include empty region (which is air)

I hope I explained it well. If you don't understand something, please tell me

[Maksim]

As I understand, maybe I can just reindex a matrix and remove zeros from it, but how to do it properly so it will match with the VERT array?

Answer 1

[Suraj Kumar]

Hi @Maksim,

To map values from a color intensity matrix of an image to a mesh obtained from the same image, you can refer to the following steps:

1. Load the necessary data using the 'load' function in MATLAB. This will import the intensity matrix (gray_matrix), mesh nodes (nodes), and triangles (triangles).

2. Iterate over each node in the mesh to map intensity values from the matrix. Convert the node's (x, y) coordinates into matrix indices, retrieve the corresponding intensity value, and multiply it by the Modulus of Elasticity.

3. Prepare the mapped node or element values for export to ANSYS by writing them to a file in a suitable format, such as CSV, using 'csvwrite' function in MATLAB.

To learn more about the 'csvwrite' function in MATLAB, please refer to the following documentation:

https://www.mathworks.com/help/matlab/ref/csvwrite.html

Hope this helps!