How can I compute a curvilinear abscissa along a non-straight path in IronPython?

Pierre Thieffry

Say I have an edge or set of edges in Mechanical which are not straight . How can I derive an abscissa to plot some quantity against?

Pierre Thieffry

There would be many libraries available in C-Python to achieve this. I'm proposing the following simple code. For a set of nodes, nodes_coords would be a dictionary whose keys are the node numbers and the values are a list of three coordinates [x,y,z]

def findClosestNode(ref_coord,node_coords):
    mindist=1e31
    minnode=-1
    for nd,coord in node_coords.items():
        dist=(ref_coord[0]-coord[0])**2+(ref_coord[1]-coord[1])**2+(ref_coord[2]-coord[2])**2
        if dist<mindist:
            mindist=dist
            minnode=nd
            
    return minnode,mindist

def getCurvilinearAbscissa(node_coords):
    local_node_coords=node_coords
    curv_absc=[]
    distances={}
    # find node with lowest X
    xmin=1e31
    for nd,coord in node_coords.items():
        if xmin>coord[0]:
            xmin=coord[0]
            ndmin=nd
    dist_idx=0
    ref_coord=node_coords[ndmin]
    distances[dist_idx]=[ndmin,0.]
    dist_idx+=1
    del local_node_coords[ndmin]
    # Now compute distance between nodes
    while len(local_node_coords.keys())>0:
        next_node,dist=findClosestNode(ref_coord,local_node_coords)
        distances[dist_idx]=[next_node,math.sqrt(dist)]
        ref_coord=node_coords[next_node]
        del local_node_coords[next_node]
        dist_idx+=1
    
    
    curv_absc=[[distances[0][0],0.]]
    
    for i in range(1,max(distances.keys())+1):
        curv_absc.append([distances[i][0],curv_absc[-1][1]+distances[i][1]])
    return curv_absc
        
mesh=ExtAPI.DataModel.MeshDataByName(ExtAPI.DataModel.MeshDataNames[0])
    
for i in my_node_ids:
    nd=mesh.NodeById(i)
    node_coords[i]=[nd.X,nd.Y,nd.Z]
    

curv_abs=getCurvilinearAbscissa(node_coords)