How do I merge one Mesh to another?

[tksuoran]

Given GEO::Mesh& destination and GEO::Mesh& source, I would like add all vertices, faces etc. from source into destination. There may already have existing vertices, faces etc. in the destination. I would like to do this without any consideration for intersections for example. Is there a simple way to achieve this?

Edit x 2: This is what I came up with - works for me, but only minimally tested. The if (dst_attribute_store == nullptr) branch is likely never used nor works as is.

void merge_attributes(GEO::AttributesManager& dst, GEO::AttributesManager& src, GEO::index_t dst_base_element)
{
    const GEO::index_t src_element_count = src.size();
    GEO::vector<std::string> attribute_names;
    src.list_attribute_names(attribute_names);
    for (std::string& attribute_name : attribute_names) {
        GEO::AttributeStore* src_attribute_store = src.find_attribute_store(attribute_name);
        GEO::AttributeStore* dst_attribute_store = dst.find_attribute_store(attribute_name);
        if (dst_attribute_store == nullptr) {
            dst_attribute_store = GEO::AttributeStore::create_attribute_store_by_element_type_name(
                src_attribute_store->element_typeid_name(),
                src_attribute_store->dimension()
            );
            dst.bind_attribute_store(attribute_name, dst_attribute_store);
        }
        const GEO::index_t new_size = dst_base_element + src_element_count;
        dst_attribute_store->resize(new_size);
        const std::size_t  element_size = src_attribute_store->element_size();
        const std::size_t  item_size    = element_size * src_attribute_store->dimension();
        const std::byte*   src_data     = static_cast<const std::byte*>(src_attribute_store->data());
              std::byte*   dst_data     = static_cast<      std::byte*>(dst_attribute_store->data());
        const std::size_t  dst_offset   = dst_base_element  * item_size;
        const std::size_t  byte_count   = src_element_count * item_size;
        memcpy(dst_data + dst_offset, src_data, byte_count);
    }
}

(from https://github.com/tksuoran/erhe/blob/cdda5d8b8a0a0069e20861c66394a44ac03941a6/src/erhe/geometry/erhe_geometry/geometry.cpp#L616-L641)

[BrunoLevy]

Hello,
For now there is no API function to do that (I will add it in a future version), but it is quite easy,
There is an example in Graphite, here

[tksuoran]

Does this also handle attributes attached to vertices, facets, facet_corners, edges? I didn't immediately spot where that would have been done.

[BrunoLevy]

No it does not !
I plan to write mesh append with attribute support as an API function, but it is very subtle to write (and it is the reason why I have not written this function yet)...

[tksuoran]

Edit: I've now been able to test my code, it works for me, for the paths that I've tested..