Function triangularize

utils/algorithms.cpp:63–121

}

std::optional<std::vector<size_t>> triangularize(const std::vector<Vec3> &points)
{
    const size_t n = points.size();
    if (n < 3)
    {
        return std::nullopt; // insufficient points
    }

    const Vec3 normal = Vec3::normal(points);

    if (normal.magnitude() < 1e-12f)
    {
        return std::nullopt; // degenerate polygon
    }

    // list of vertex indexes
    std::vector<size_t> indices(n);
    std::iota(indices.begin(), indices.end(), 0);

    std::vector<size_t> result;

    // ears search
    while (indices.size() > 3)
    {
        bool ear_found = false;

        for (std::size_t i = 0; i < indices.size(); i++)
        {
            if (is_ear(i, points, indices, normal))
            {
                // adding triangle
                size_t prev = indices[(i + indices.size() - 1) % indices.size()];
                size_t curr = indices[i];
                size_t next = indices[(i + 1) % indices.size()];

                result.push_back(prev);
                result.push_back(curr);
                result.push_back(next);

                // removing current ear
                indices.erase(std::next(indices.begin(), static_cast<std::ptrdiff_t>(i)));
                ear_found = true;
                break;
            }
        }

        if (!ear_found)
        {
            return std::nullopt; // no valid ear
        }
    }

    // adding last triangle
    result.push_back(indices[0]);
    result.push_back(indices[1]);
    result.push_back(indices[2]);

    return result;