How to export node normal vectors at each node belonging to a nodal named selection into a csv?

Rohith Patchigolla

I have a nodal named selection in Ansys Mechanical. I would like to export the node normal vectors at each of these nodes into a csv file. How can we do this?

Rohith Patchigolla

We can do this in Mechanical using Mechanical scripting and Python.

Below is an example script (there is still scope for improvement in cases where a node shares multiple faces), which takes nodal named selection name as an input, loops over nodes, gets the face ID of the node, and gets the normal. Once loop is completed, it writes out a csv.

import csv
import os
 
# Name of the output CSV file
output_file_path = "D:\del"
output_file_name = "vector_data.csv"
named_selection_name = "NS_Vectors_2"
 
fullpath = os.path.join(output_file_path, output_file_name)
 
nodalNS = DataModel.GetObjectsByName(named_selection_name)[0]
nodeIDs = nodalNS.Location.Ids
vecNormalX = []
vecNormalY = []
vecNormalZ = []
matrix_full = []
 
def writeCSV(t1,fileName):
    ExtAPI.Log.WriteMessage('my File name ' + fileName)
    with open(fileName , 'w') as f:
        for line in t1:
            for col in line:
                #For Non-German
                #f.write(str(col) + ', ')
                #For German OS 
                f.write(str(col).replace(".",",") + '; ')
            f.write('\n')
 
for nodeId in nodeIDs:
    meshData = DataModel.MeshDataByName(DataModel.MeshDataNames[0])
    meshNode = meshData.NodeById(nodeId) 
    base_point = meshNode.X, meshNode.Y, meshNode.Z
 
    geoIDs = meshNode.GeoEntityIds
    connectedFaceIDs = []
    for geoID in geoIDs:
        if DataModel.GeoData.GeoEntityById(geoID).Type == GeoCellTypeEnum.GeoFace:
            connectedFaceIDs.append(geoID)
 
    if len(connectedFaceIDs) > 1:
        print "Node shared by multiple faces. Only printing of vectors is coded"
        for faceID in connectedFaceIDs:
            myface = DataModel.GeoData.GeoEntityById(faceID)
            u,v = myface.ParamAtPoint(base_point)
            vec_normal = myface.NormalAtParam(u,v)  #Normal Vector to the face at given node
            print(vec_normal)
    else:
        myface = DataModel.GeoData.GeoEntityById(connectedFaceIDs[0])
        u,v = myface.ParamAtPoint(base_point)
        vec_normal = myface.NormalAtParam(u,v)  #Normal Vector to the face at given node
        print(vec_normal)
        vecNormalX.append(vec_normal[0])
        vecNormalY.append(vec_normal[1])
        vecNormalZ.append(vec_normal[2])
 
matrix_full = [[nodeIDs[i], vecNormalX[i], vecNormalY[i], vecNormalZ[i]] for i in range(len(nodeIDs))]
writeCSV(matrix_full,fullpath)