addMetadata

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Synopsis

addMetadata [-channelType string] [-indexType string] [-streamName string] [-structure string]

addMetadata is undoable, queryable, and NOT editable.

Defines the attachment of a metadata structure to one or more selected objects. This creates a placeholder with an empty metadata Stream for later population through the editMetadata command. It's similar in concept to the addAttr command for nodes - an attribute is added but no data is actually set.

When assigning a metadata structure you must specify these flags - channelType is the metadata channel type (e.g. "vertex"), streamName is the name of the metadata stream to be created, and structure is the name of the structure type defining the contents of the metadata. The indexType flag is optional. If it is not present then the index will be presumed to be a standard numerical value.

You can query metadata information at a variety of levels. See the table below for a full list of the queryable arguments. In each case the specification of any of the non-queried arguments filters the list of metadata to be examined during the query. For all queries a single object must be selected for querying.

For example querying the channelType flag with no other arguments will return the list of all Channel types on the selected object that contain any metadata. Querying the channelType flag with the indexType flag specified will return only those channel types containing metadata streams that use that particular type of index.

• Query the channelType flag to return the list of any channel types that have metadata.
• Specify the channelType and streamName flags and query the structure flag to return the name of the structure assigned to the given stream (if any).
• Specify a channelType and query the streamName to return the list of all streams assigned to that particular channel type.
• If you query the streamName without a specific channelType then it returns a list of pairs of (channelType, streamName) for all metadata streams.

Flag Combinations:

ChannelType IndexType StreamName Structure   Create   Can Query
     0          0          0         0         X        ChannelType, StreamName, Structure
     0          0          0         1         X        ChannelType, StreamName, IndexType
     0          0          1         0         X        ChannelType, Structure, IndexType
     0          0          1         1         X        ChannelType, IndexType
     0          1          0         0         X        ChannelType, StreamName, Structure
     0          1          0         1         X        ChannelType, StreamName
     0          1          1         0         X        ChannelType, Structure
     0          1          1         1         X        ChannelType
     1          0          0         0         X        StreamName, Structure, IndexType
     1          0          0         1         X        StreamName, IndexType
     1          0          1         0         X        Structure, IndexType
     1          0          1         1        (a)       IndexType
     1          1          0         0         X        StreamName, Structure
     1          1          0         1         X        StreamName
     1          1          1         0         X        Structure
     1          1          1         1        (b)       X
    (a) Assign an empty metadata stream with default index type
    (b) Assign an empty metadata stream with the named index type

Return value

In query mode, return type is based on queried flag.

Keywords

Related

Flags

Long name (short name)	Argument types	Properties
-channelType(-cht)	string
Name of the Channel type to which the structure is to be added (e.g. "vertex"). In query mode, this flag can accept a value.
-indexType(-idt)	string
Name of the index type the new Channel should be using. If not specified this defaults to a simple numeric index. Of the native types only a mesh "vertexFace" channel is different, using a "pair" index type. In query mode, this flag can accept a value.
-streamName(-stn)	string
Name of the empty stream being created. In query mode not specifying a value will return a list of streams on the named channel type. In query mode, this flag can accept a value.
-structure(-str)	string
Name of the structure which defines the metadata to be attached to the object. In query mode this will return the name of the structure attached at a given stream. In query mode, this flag can accept a value.

Flag can appear in Create mode of command	Flag can appear in Edit mode of command
Flag can appear in Query mode of command	Flag can be used more than once in a command.

MEL examples

polyPlane -n p -ch off;
select -r "pShape";
dataStructure -format "raw" -asString "name=IdStruct:int32=ID";
dataStructure -format "raw" -asString "name=OffStruct:float=Offset";
dataStructure -format "raw" -asString "name=OrgStruct:float[3]=Origin Point";
addMetadata -streamName "IdStream" -channelType "vertex" -structure "IdStruct";
addMetadata -streamName "OffStream" -channelType "vertex" -structure "OffStruct";
addMetadata -streamName "OrgStream" -channelType "edge" -structure "OrgStruct";
addMetadata -streamName "VFStream" -channelType "vertexFace" -indexType "pair" -structure "OrgStruct";
// Query for the list of all channel types possessing metadata
addMetadata -query -channelType;
// Return: edge vertex vertexFace //
// Query for the structure assigned to a specific stream
addMetadata -channelType "vertex" -streamName "OffStream" -query -structure;
// Return: OffStruct //
// Query for the list of all streams on a specific channel type
addMetadata -channelType "vertex" -query -streamName;
// Return: IdStream OffStream //
// Query for the list of all streams
addMetadata -query -streamName;
// Return: IdStream OffStream OrgStream VFStream //
// You can combine queries to answer more general questions about the
// metadata on an object. For example suppose you wanted to know the
// index type used by all Streams on the "vertex" Channel.
// First extract the list of Streams on the Channel
string $streams[] = `addMetadata -channelType "vertex" -query -streamName`;
int $i;
// Loop through each Stream, querying the IndexType only for that Stream
for( $i=0; $i < size( $streams ); ++$i )
{
	string $indexType = `addMetadata -channelType "vertex" -streamName $streams[$i] -query -indexType`;
	print ( "Index type on " + $streams[$i] + " is " + $indexType + "\n" );
}