Houdini - Attribute Wrangle VEX - Delete small floating pieces by number of primitives (Assemble SOP)

wrangle-attr---delete-small-floating-pieces-numprim-assemblesop.c

// Houdini - Assemble SOP > Attribute Wrangle SOP
// Delete small floating pieces by number of primitives
//
// To be used inside the VEXpression parameter of an Attribute Wrangle SOP
// with the "Run Over" mode set to "Detail (only once)".
// The geometry must be assembled first using an Assemble SOP
// with the "Create Packed Geometry" option disabled
// and the "Output Prefix" set or linked to assemble_output_prefix.
//string assemble_output_prefix = chs('../assemble1/outside_group');
string assemble_output_prefix = 'piece';

// List all of the unique 'name' values in the geo (e.g. piece0, piece1, etc.)
string pieces_names[];
for (int piece_num = 0; piece_num < nuniqueval(0, 'primitive', 'name'); piece_num++) {
  string piece_name = sprintf('%s%d', assemble_output_prefix, piece_num);
  append(pieces_names, piece_name);
}

// Find the "largest" piece (i.e. the one with the most primitives) in the list
int max_count = 0;
int largest_piece_id;
foreach (int piece_id; string piece_name; pieces_names) {
  int uniq_count = findattribvalcount(0, 'primitive', 'name', piece_name);
  if (uniq_count > max_count) {
    max_count = uniq_count;
    largest_piece_id = piece_id;
  }
}

// Delete all of the primitives that are not part of the largest piece
removeindex(pieces_names, largest_piece_id);
foreach (int piece_id; string piece_name; pieces_names) {
  int total_prim_in_piece = findattribvalcount(0, 'primitive', 'name', piece_name);
  for (int prim_id_in_piece = 0; prim_id_in_piece < total_prim_in_piece; prim_id_in_piece++) {
    int prim_to_del_id = findattribval(0, 'primitive', 'name', piece_name, prim_id_in_piece);
    removeprim(0, prim_to_del_id, 1);
  }
}