#include <MPxMayaAsciiFilter.h>

Class Description

Translator to output filtered Maya ASCII files.

MPxMayaAsciiFilter allows output to the Maya ASCII (.ma) file format to be filtered by a plug-in. The file is output using the same internal mechanism that is used for normal Maya ASCII output, but allows your plug-in to prevent certain lines (such as createNodes or connectAttrs) from being output to the file. In addition, it allows you to write directly to the file at specific points during output.

MPxMayaAsciiFilter allows your plug-in to write out files similar to Maya ASCII in a custom format. It can be used, for example, to partition a scene into several files, each of which has been filtered to write out different parts of the scene. Note that the order of the file cannot be changed - for example, connectAttrs are always written after createNodes - but it does allow you to control which connectAttrs and createNodes are output.

MPxMayaAsciiFilter inherits from MPxFileTranslator. It overrides the haveWriteMethod(), haveReadMethod(), reader(), and writer() methods in MPxFileTranslator in such a way that the internal Maya mechanism for reading and writing Maya ASCII files is used. Because of this, it is not advised that you override these methods in your plug-in. If you do, make sure you first call these methods in MPxMayaAsciiFilter. A pseudo-code example is shown here:

MyAsciiFilter::writer(...)
{
    // do something before writing to file here
    ...
    // we will now write to the file
    MStatus result = MPxMayaAsciiFilter::writer(...);
    if (result == MStatus::kSuccess)
    {
        ... // do something after writing the file here
    }
    return result;
}

To determine if a given line should be output, override the methods writesCreateNode(), writesSetAttr() and so on. Each of these methods takes as its arguments the relevant data which is about to be processed and your plug-in can use this to determine whether or not the line will be output.

For example, you may want to write out everything but render layer data. The code to do this might look something like what is shown here:

bool
MyAsciiFilter::writesCreateNode( const MObject& node )
{
    if (node.hasFn(MFn::kRenderLayer))
    {
        return true;
    }
    return false;
}
bool
MyAsciiFilter::writesConnectAttr( const MPlug& srcPlug,
                                  const MPlug& destPlug )
{
    if (srcPlug.node().hasFn(MFn::kRenderLayer) ||
        dstPlug.node().hasFn(MFn::kRenderLayer))
    {
        return true;
    }
    return false;
}

Note that writesConnectAttr() has to be overridden as well (as would writesSetAttr(), writesSelectAttr(), and so on). This is because each line is handled separately, and nothing clever is done in the base class' implementation of writesConnectAttr(), such as having a default behaviour of only outputting connectAttrs for nodes that are being output. This gives you the most flexible control over what will be written.

If you were using this class to save a segmented file, a master file might have to know about the locations of each of the segments. If your file saved everything but render layers in one file, and render layers in another, the first file might need to contain a pointer to the second, so that when the first file is loaded the second gets read into memory too. To do this, you would use MPxMayaAsciiFilter's ability to write directly to the stream during file output.

You can write to the stream during output by overriding the methods writePreCreateNodesBlock(), writePostCreateNodesBlock() and so on. These give you a simple mechanism to write directly to the file. Each of these methods take an MPxMayaAsciiFilterOutput as its only argument. To write to the file, simply use the output operator (MPxMayaAsciiFilterOutput::operator<<() ) and output the string you wish.

In the example above, the pointer to the render layer file might be inserted into the main file after all nodes have been created. The code to do this would look something like what is shown here:

MStatus
MyAsciiFilter::writePostCreateNodesBlock( MPxMayaAsciiFilterOutput& fileIO )
{
    fileIO << "eval(\"importRenderLayerFile \\\"MyLayerFile.maf\\\";\")\n";
}

In the above example, after the createNode block was output, the line

eval("importRenderLayerFile \"MyLayerFile.maf\"");

was output. When the file is read in, Maya would reach the line above and execute it like any other MEL command. It is assumed in this example that there would be a custom command plug-in called importRenderLayerFile which would do the work of actually importing the layer file.

Note: MPxMayaAsciiFilter gives you the ability to create your own custom file formats based on standard Maya ASCII files. However, Autodesk does not support such custom files as they will not, by definition, be standard Maya ASCII files.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

Inheritance diagram for MPxMayaAsciiFilter:

Public Member Functions
	MPxMayaAsciiFilter ()
	The class constructor.

virtual	~MPxMayaAsciiFilter ()
	The class destructor.

virtual bool	haveWriteMethod () const
	Overrides MPxFileTranslator::haveWriteMethod() to indicate that this translator has a write method. More...

virtual bool	haveReadMethod () const
	Overrides MPxFileTranslator::haveReadMethod() to indicate that this translator has a read method. More...

virtual MStatus	reader (const MFileObject &file, const MString &optionsString, FileAccessMode mode)
	Reader method for the ascii filter translator. More...

virtual MStatus	writer (const MFileObject &file, const MString &optionsString, FileAccessMode mode)
	Writer method for the ascii filter translator. More...

Public Member Functions inherited from MPxFileTranslator
	MPxFileTranslator ()
	The class constructor.

virtual	~MPxFileTranslator ()
	The class destructor.

virtual bool	haveNamespaceSupport () const
	When a file is imported or referenced into an existing scene, there is the possibility that nodes in the incoming file will have the same names as nodes already in the scene. More...

virtual bool	haveReferenceMethod () const
	This method is called by Maya to see if the translator implements its own custom file referencing. More...

virtual MString	defaultExtension () const
	This routine is called by Maya whenever it needs to know the default extension of a translator. More...

virtual MString	filter () const
	This virtual method may be overloaded in a derived class to set the filter extension that will be used by the file dialog. More...

virtual bool	canBeOpened () const
	This routine is called by Maya while it is executing in the MPxFileTranslator constructor. More...

virtual MPxFileTranslator::MFileKind	identifyFile (const MFileObject &file, const char *buffer, short size) const
	This routine is called by Maya when a file selection dialog accesses a new directory. More...

Protected Member Functions
const MFileObject	file () const
	Returns the MFileObject associated with the file currently being read or written, allowing access to the file's name, path and so on. More...

virtual MStatus	processReadOptions (const MString &optionsString)
	Allows the translator to handle any options passed into the reader() method, above. More...

virtual MStatus	processWriteOptions (const MString &optionsString)
	Allows the translator to handle any options passed into the reader() method, above. More...

virtual bool	writesRequirements () const
	Determines if "requires" commands should be written in the file. More...

virtual bool	writesMetadata () const
	Asserts that "dataStructure/addMetadata/applyMetadata" commands should be written in the file. More...

virtual bool	writesCreateNode (const MObject &node) const
	Determines if a "createNode" command should be written for a particular node. More...

virtual bool	writesSetAttr (const MPlug &srcPlug) const
	Determines if a "setAttr" command should be written for a particular node. More...

virtual bool	writesConnectAttr (const MPlug &srcPlug, const MPlug &destPlug) const
	Determines if a "connectAttr" command should be written for a particular node. More...

virtual bool	writesDisconnectAttr (const MPlug &srcPlug, const MPlug &destPlug) const
	Determines if a "disconnectAttr" command should be written for a particular connection. More...

virtual bool	writesParentNode (const MDagPath &parent, const MDagPath &child) const
	Determines if a "parent" command should be written for a particular parent and child. More...

virtual bool	writesSelectNode (const MObject &node) const
	Determines if a "select" command should be written for a particular node. More...

virtual bool	writesFileReference (const MFileObject &referenceFile) const
	Determines if a "fileReference" command should be written for a file. More...

virtual MStatus	writePostHeader (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file after the header block. More...

virtual MStatus	writePostRequires (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file after the requires block. More...

virtual MStatus	writePreCreateNodesBlock (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file before the create nodes block. More...

virtual MStatus	writePostCreateNodesBlock (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file after the create nodes block. More...

virtual MStatus	writePreConnectAttrsBlock (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file before the connect attrs block. More...

virtual MStatus	writePostConnectAttrsBlock (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file after the connect attrs block. More...

virtual MStatus	writePreTrailer (MPxMayaAsciiFilterOutput &fileIO)
	Allows data to be written out to the file before the trailer block. More...

Additional Inherited Members
Public Types inherited from MPxFileTranslator
enum	MFileKind { kIsMyFileType, kCouldBeMyFileType, kNotMyFileType }
	How the translator identifies this file. More...

enum	FileAccessMode { kUnknownAccessMode, kOpenAccessMode, kReferenceAccessMode, kImportAccessMode, kSaveAccessMode, kExportAccessMode, kExportActiveAccessMode }
	Type of file access. More...

Static Public Member Functions inherited from MPxFileTranslator
static MPxFileTranslator::FileAccessMode	fileAccessMode ()
	This routine returns the fileAccess mode maya is currently in. More...

Member Function Documentation

bool haveWriteMethod ( ) const

virtual

Overrides MPxFileTranslator::haveWriteMethod() to indicate that this translator has a write method.

In general this should not be overridden.

Returns: true

Reimplemented from MPxFileTranslator.

bool haveReadMethod ( ) const

virtual

Overrides MPxFileTranslator::haveReadMethod() to indicate that this translator has a read method.

In general this should not be overridden.

Returns: true

Reimplemented from MPxFileTranslator.

MStatus reader	(	const MFileObject &	file,
		const MString &	optionsString,
		FileAccessMode	mode
	)

virtual

Reader method for the ascii filter translator.

In general this should not be overridden, since internal Maya methods are called in this method.

Note: To process any options passed in in the optionsString variable, subclasses should override the processReadOptions() method, below.

Parameters

[in]	file	The file to be read
[in]	optionsString	Any file options to be handled. Passed to processReadOptions(), below
[in]	mode	The access mode (read or import). Currently this is ignored

Returns

MS::kSuccess file read was successful
MS::kFailure an error occurred while reading the file

Reimplemented from MPxFileTranslator.

MStatus writer	(	const MFileObject &	file,
		const MString &	optionsString,
		FileAccessMode	mode
	)

virtual

Writer method for the ascii filter translator.

In general this should not be overridden, since internal Maya methods are called in this method.

Note: To process any options passed in in the optionsString variable, subclasses should override the processWriteOptions() method, below.

Parameters

[in]	file	The file to be read
[in]	optionsString	Any file options to be handled. Passed to processWriteOptions(), below
[in]	mode	The access mode (save, export, or export active). Currently this is ignored.

Returns

MS::kSuccess file read was successful
MS::kFailure an error occurred while reading the file

Reimplemented from MPxFileTranslator.

const MFileObject file ( ) const

protected

Returns the MFileObject associated with the file currently being read or written, allowing access to the file's name, path and so on.

Returns: The file object. Only valid while a read or write is happpening

MStatus processReadOptions ( const MString & optionsString )

protectedvirtual

Allows the translator to handle any options passed into the reader() method, above.

This call is made before the file is actually read. The default implementation does nothing.

Parameters

[in] optionsString The file options to be handled.

Returns: MS::kSuccess Options were properly handled, and file read can commence. If any other value is returned, file read is aborted.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

MStatus processWriteOptions ( const MString & optionsString )

protectedvirtual

Allows the translator to handle any options passed into the reader() method, above.

This call is made before the file is actually read. The default implementation does nothing.

Parameters

[in] optionsString The file options to be handled.

Returns: MS::kSuccess Options were properly handled, and file read can commence. If any other value is returned, file write is aborted.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

bool writesRequirements ( ) const

protectedvirtual

Determines if "requires" commands should be written in the file.

By default true is always returned.

Returns: bool true if "requires" commands should be written; false otherwise.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

bool writesMetadata ( ) const

protectedvirtual

Asserts that "dataStructure/addMetadata/applyMetadata" commands should be written in the file.

Normally these are always written but you may want to override this to prevent metadata from being added to Maya files if you export it in other ways.

Returns: bool true if metadata commands should be written; false otherwise.

bool writesCreateNode ( const MObject & node ) const

protectedvirtual

Determines if a "createNode" command should be written for a particular node.

By default this method returns true for all nodes.

Parameters

[in] node The node in question.

Returns: True if the createNode should be written, false otherwise.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

bool writesSetAttr ( const MPlug & srcPlug ) const

protectedvirtual

Determines if a "setAttr" command should be written for a particular node.

By default this method returns true for all plugs.

Parameters

[in] srcPlug The plug to be set.

Returns: bool true if the setAttr should be written; false otherwise.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

bool writesConnectAttr	(	const MPlug &	srcPlug,
		const MPlug &	destPlug
	)		const

protectedvirtual

Determines if a "connectAttr" command should be written for a particular node.

By default this method returns true for all connections.

Parameters

[in]	srcPlug	The source plug in the connection.
[in]	destPlug	The destination plug in the connection.

Returns: bool true if the connectAttr should be written; false otherwise.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

bool writesDisconnectAttr	(	const MPlug &	srcPlug,
		const MPlug &	destPlug
	)		const

protectedvirtual

Determines if a "disconnectAttr" command should be written for a particular connection.

By default this method returns true for all connection.

Parameters

[in]	srcPlug	The source plug in the connection.
[in]	destPlug	The destination plug in the connection.

Returns: bool true if the disconnectAttr should be written; false otherwise.

bool writesParentNode	(	const MDagPath &	parent,
		const MDagPath &	child
	)		const

protectedvirtual

Determines if a "parent" command should be written for a particular parent and child.

By default this method returns true for all parents and children.

Parameters

[in]	parent	The dag path to the parent.
[in]	child	The dag path to the child.

Returns: bool true if the disconnectAttr should be written; false otherwise.

bool writesSelectNode ( const MObject & node ) const

protectedvirtual

Determines if a "select" command should be written for a particular node.

By default this method returns true for all nodes.

Parameters

[in] node The node to select

Returns: bool true if the select should be written; false otherwise.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

bool writesFileReference ( const MFileObject & referenceFile ) const

protectedvirtual

Determines if a "fileReference" command should be written for a file.

By default this method returns true for all files.

Parameters

[in] referenceFile The file to be referenced.

Returns: bool true if the fileReference should be written; false otherwise.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

MStatus writePostHeader ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file after the header block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: bool true if the disconnectAttr should be written; false otherwise.

MStatus writePostRequires ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file after the requires block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: MS::kSuccess Output was successfull.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

MStatus writePreCreateNodesBlock ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file before the create nodes block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: MS::kSuccess Output was successfull.

MStatus writePostCreateNodesBlock ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file after the create nodes block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: MS::kSuccess Output was successfull.

Examples:: filteredAsciiFile/filteredAsciiFile.cpp.

MStatus writePreConnectAttrsBlock ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file before the connect attrs block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: MS::kSuccess Output was successfull.

MStatus writePostConnectAttrsBlock ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file after the connect attrs block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: MS::kSuccess Output was successfull.

MStatus writePreTrailer ( MPxMayaAsciiFilterOutput & filterOutput )

protectedvirtual

Allows data to be written out to the file before the trailer block.

By default this method does nothing.

Parameters

[in] filterOutput the output stream to be written to (using the << operator)

Returns: MS::kSuccess Output was successfull.

The documentation for this class was generated from the following files:

MPxMayaAsciiFilter.h
MPxMayaAsciiFilter.cpp

MPxMayaAsciiFilter Class Reference

Class Description

Public Member Functions

Protected Member Functions

Additional Inherited Members

Member Function Documentation