read_anchor()

MAYAFLUX_API std::optional< glm::vec3 > MayaFlux::Nexus::read_anchor	(	const std::shared_ptr< Buffers::VKBuffer > &	buf,
		const std::optional< uint32_t > &	index
	)

Anchor of a buffer's geometry in its own stored coordinates.

The position of the vertex at index, else the surface centroid, else the vertex mean for a mesh without faces. A point or path buffer reports the mean of its vertices; an InstanceNetworkBuffer, with no index, the centre of its bounds. Blocks for a ComputeMeshBuffer and for a buffer a field processor drives.

Parameters

buf	Buffer to read.
index	Vertex to anchor at, if any.

Returns

The anchor, or nullopt when no geometry can be read from the buffer.

Definition at line 213 of file Survey.cpp.

{
    if (const auto cloud = cloud_of(buf); cloud && !cloud->positions.empty()) {
        if (!index) {
            return Kinesis::centroid(cloud->positions);
        }
        return *index < cloud->positions.size()
            ? std::optional<glm::vec3> { cloud->positions.at(*index) }
            : std::nullopt;
    }
 
    if (const auto instances = std::dynamic_pointer_cast<Buffers::InstanceNetworkBuffer>(buf);
        instances && !index) {
        const auto bounds = instance_bounds(instances);
        return bounds ? std::optional<glm::vec3> { bounds->center() } : std::nullopt;
    }
 
    const auto mesh = snapshot_mesh(buf);
    if (!mesh) {
        return std::nullopt;
    }
 
    const auto bytes = vertex_bytes(*mesh);
    if (bytes.empty()) {
        return std::nullopt;
    }
 
    const size_t stride = mesh->layout.stride_bytes;
    const size_t offset = position_offset(mesh->layout);
 
    if (index) {
        return Kinesis::position_at(bytes, stride, offset, *index);
    }
 
    if (const auto* faces = std::get_if<std::vector<uint32_t>>(&mesh->index_variant);
        faces && !faces->empty()) {
        return Kinesis::surface_centroid(bytes, stride, offset, *faces);
    }
    return Kinesis::centroid(bytes, stride, offset);
}

References index, offset, position_offset, and read_anchor().

Referenced by make_attachment(), read_anchor(), and recenter_attachment().

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