ImplicitSurfaceNetwork/network_process/src/post_topo/patch_propagation.cpp

#include <stack>
#include <queue>

#include <post_topo.hpp>

std::vector<dynamic_bitset<>> propagate_subface_labels(size_t                                    subface_count,
                                                       const std::vector<polygon_face_t>&        faces,
                                                       const std::vector<std::vector<uint32_t>>& patches,
                                                       const std::vector<std::vector<uint32_t>>& arrangement_cells,
                                                       const std::vector<uint32_t>&              shell_of_half_patch,
                                                       const std::vector<std::vector<uint32_t>>& shells,
                                                       const std::vector<uint32_t>&              shell_to_cell)
{
    // in turn: [subface_index][cell_index] = sign
    std::vector<dynamic_bitset<>> cell_subface_signs(subface_count, dynamic_bitset<>(arrangement_cells.size()));

    std::vector<bool>                  visited_cells(arrangement_cells.size(), false);
    std::vector<bool>                  visited_subfaces(subface_count, false);
    std::vector<std::vector<uint32_t>> cell_indices_of_inactive_subfaces(subface_count);
    std::queue<uint32_t>               Q{};
    dynamic_bitset<>                   opposed_cells(arrangement_cells.size());
    std::vector<uint32_t>              unique_opposed_cells{};

    Q.emplace(0);
    while (!Q.empty()) {
        const auto cell_index = Q.front();
        const auto cell       = arrangement_cells[cell_index];
        Q.pop();

        if (!visited_cells[cell_index]) {
            visited_cells[cell_index] = true;
            opposed_cells.reset();
            unique_opposed_cells.clear();

            for (auto shell : cell) {
                for (auto half_patch : shells[shell]) {
                    auto subface_label = faces[patches[half_patch / 2][0]].subface_index;
                    // CAUTION: we assume that the sign is 1 when the surface is inside the sdf before
                    // but in blobtree we assume that the sign is 0 when the surface is inside the sdf
                    // so we need to flip the sign here
                    // EDIT: to keep sign operation nice and easy, we'll just keep the sign being 1 when the surface is inside
                    // the sdf
                    bool sign          = (half_patch % 2 == 0) ? 1 : 0;
                    auto oppose_cell   = shell_to_cell[shell_of_half_patch[sign ? (half_patch + 1) : (half_patch - 1)]];
                    // bool sign          = (half_patch % 2 == 0) ? 0 : 1;
                    // auto oppose_cell   = shell_to_cell[shell_of_half_patch[!sign ? (half_patch + 1) : (half_patch - 1)]];

                    // sign broadcast
                    if (oppose_cell != cell_index) {
                        if (!opposed_cells[oppose_cell]) {
                            for (uint32_t si = 0; si < subface_count; ++si)
                                cell_subface_signs[si][oppose_cell] = cell_subface_signs[si][cell_index];
                            opposed_cells[oppose_cell] = true;
                            unique_opposed_cells.emplace_back(oppose_cell);
                            if (!visited_cells[oppose_cell]) Q.emplace(oppose_cell);
                        }
                        cell_subface_signs[subface_label][oppose_cell] = !sign;
                    }

#ifndef RELEASE_BRANCH
                    if (visited_subfaces[subface_label] != false && cell_subface_signs[subface_label][cell_index] != sign) {
                        throw std::runtime_error("ERROR: Inconsistent Cell Function Labels.");
                    }
#endif

                    cell_subface_signs[subface_label][cell_index] = sign;
                    visited_subfaces[subface_label]               = true;
                    // propagate the function signs to all previously inactive cells
                    if (cell_indices_of_inactive_subfaces[subface_label].size() > 0) {
                        for (const auto cell_index : cell_indices_of_inactive_subfaces[subface_label]) {
                            cell_subface_signs[subface_label][cell_index] = sign;
                        }
                        cell_indices_of_inactive_subfaces[subface_label].clear();
                    }
                }
            }

            // fetch inactive subface index
            for (uint32_t subface_index = 0; subface_index < subface_count; subface_index++) {
                if (visited_subfaces[subface_index] == false) {
                    cell_indices_of_inactive_subfaces[subface_index].emplace_back(cell_index);
                    for (const auto& other_cell_index : unique_opposed_cells) {
                        cell_indices_of_inactive_subfaces[subface_index].emplace_back(other_cell_index);
                    }
                }
            }
        }
    }

#ifndef RELEASE_BRANCH
    for (size_t i = 0; i < subface_count; ++i) {
        if (visited_subfaces[i] == false) { throw std::logic_error("ERROR: Still have sign-unknown subfaces."); }
    }
#endif

    return cell_subface_signs;
}

dynamic_bitset<> filter_cells_by_boolean(const baked_blobtree_t& tree, std::vector<dynamic_bitset<>>& cell_primitive_signs)
{
    struct compact_node_info {
        dynamic_bitset<> cell_signs{};
        uint32_t         parent_index{};
    };

    std::stack<compact_node_info> stacked_nodes{};
    auto                          iter = tree.nodes.begin();
    stacked_nodes.emplace(compact_node_info{std::move(cell_primitive_signs[iter->primitive_index]), iter->parent_index});

    iter++;
    while (iter != tree.nodes.end()) {
        // each out iteration must start with leaf node, only 1 leaf node is absorbed in one iteration
        assert(iter->is_primitive_node());
        compact_node_info temp_info{std::move(cell_primitive_signs[iter->primitive_index]), iter->parent_index};
        iter++; // to parent or neighboring node
        while (!stacked_nodes.empty() && temp_info.parent_index == stacked_nodes.top().parent_index) {
            // do bool operation, util meet next primitive node.
            assert(iter->is_operation_node());

            // HINT: other_cell_signs here should always be left nodes
            const auto& other_cell_sign = stacked_nodes.top().cell_signs;
            switch (iter->get_operation()) {
                case internal::eNodeOperation::unionOp:        temp_info.cell_signs |= other_cell_sign; break;
                case internal::eNodeOperation::intersectionOp: temp_info.cell_signs &= other_cell_sign; break;
                case internal::eNodeOperation::differenceOp:
                    // stacked nodes are always left childs
                    temp_info.cell_signs = other_cell_sign & ~temp_info.cell_signs;
                    break;
                default: throw std::runtime_error("ERROR: baked blobtree with unknown type operation node"); break;
            }
            temp_info.parent_index = iter->parent_index;

            stacked_nodes.pop();
            iter++; // to parent or neighboring node
        }
        stacked_nodes.emplace(std::move(temp_info));
    }

    assert(stacked_nodes.size() == 1);
    assert(stacked_nodes.top().parent_index == 0xFFFFFFFF);

    // sign 0 in blobtree means inside, so we need to flip the sign
    // EDIT: no need to flip signs here
    return stacked_nodes.top().cell_signs;
}