VEX code for finding centroids of clusters made with Houdini cluster node

find_centroid_of_clusters.cpp

// The cluster node in houdini creates 2 groups:
// attributepoints and clusterpoints
// but I need an attribute to store, for each cluster, the centroid
// So what I've come up is to...

// 1. Create an attribute on each point, called centroid 
// and formatted like this: "{index_of_the_point}_{index_of_the_cluster}"
// See set_centroid_attribute.cpp

// 2. Use it so that each point will loop in all other points
// until he finds a centroid attribute the other point that is not 1_1
// and where the {index_of_the_cluster} matches its own cluster
// See the while loop below

// Split the centroid attribute so that we know what we're looking for
string splitted[] = split(s@centroid, "_");
int point_index = atoi(splitted[0]);
int cluster_index = atoi(splitted[1]);

// Only if the current point is not the average point
// (this could also be done with the inpointgroup)
if (point_index == 1 && cluster_index == 1){
    
    int p = 0;
    int maximum_iter = @numpt;
    while (p < maximum_iter){
        
        // Skip this point
        if (p == @ptnum){
            p++;
            continue;
        }
        
        // Split the centroid attr on the other point
        int s;
        string centroid_attr = pointattrib(0, "centroid", p, s);
        
        string other_splitted[] = split(centroid_attr, "_");
        int other_point_index = atoi(other_splitted[0]);
        int other_cluster_index = atoi(other_splitted[1]);
        
        // Look for the point with a similar cluster
        if (other_point_index != 1 && other_cluster_index == @cluster){
            
            int success;
            vector centroid_pos = pointattrib(0, "P", other_point_index, success);
            
            v@centroid_pos = centroid_pos;
            // For debugging, use the normals to visualize if things are correct
            @N = normalize(@P - centroid_pos);
            break;
        }
        
        p++;
    }
}

set_centroid_attribute.cpp

if (inpointgroup(0, "averagepoints", @ptnum)){
    s@centroid = sprintf("%s_%s", i@ptnum, i@cluster);
}
else {
    s@centroid = "1_1";
}