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# customImagePlane.cpp

    //-
    // ==========================================================================
    // Copyright 1995,2006,2008 Autodesk, Inc. All rights reserved.
    //
    // Use of this software is subject to the terms of the Autodesk
    // license agreement provided at the time of installation or download,
    // or which otherwise accompanies this software in either electronic
    // or hard copy form.
    // ==========================================================================
    //+

    // Description:
    //   Demonstrates how to create your own custom image plane based on
    //   Maya's internal image plane classes. This allows API users to
    //   override the default Maya image plane behavior. This class works
    //   like typical API nodes in that it can have a compute method and
    //   can contain static attributes added by the API user.  This
    //   example class overrides the default image plane behavior and
    //   allows users to add transparency to an image plane using the
    //   transparency attribute on the node. Note, this code also
    //   illustrates how to use MImage to control the floating point
    //   depth buffer.  When useDepthMap is set to true, depth is added
    //   is added to the image such that half of the iamge is at the near
    //   clip plane and the remaining half is at the far clip plane.
    //
    //   Note, once the image plane node has been created it you must
    //   attached it to the camera shape that is displaying the node.
    //   Image planes are attached to cameras via the imagePlane message
    //   attribute on the camera shape.  To attach this example image
    //   plane you should connect the image plane's message attribute to
    //   the cameraShapes imagePlane attribute.  Note, the imagePlane
    //   attribute is a multi attribute and can hold references to
    //   multiple image planes.
    //
    //   This example works only with renderers that use node evaluation
    //   as a part of the rendering process, e.g. Maya Software. It does
    //   not work with renderes that rely on a scene translation mechanism,
    //   e.g. mental ray.
    //
    //   For example,
    //     string $imageP = `createNode customImagePlane`
    //     connectAttr -f ($imageP + ".message") "perspShape.imagePlane[0]"
    //

    #include <maya/MPxImagePlane.h>
    #include <maya/MFnPlugin.h>
    #include <maya/MImage.h>
    #include <maya/MString.h>
    #include <maya/MFnNumericAttribute.h>
    #include <maya/MFnNumericData.h>
    #include <maya/MDataHandle.h>
    #include <maya/MPlug.h>

    class customImagePlane : public MPxImagePlane
    {
    public:
                            customImagePlane();
        virtual MStatus     loadImageMap( const MString &fileName, int frame, MImage &image );

        virtual bool        getInternalValueInContext(
            const MPlug&, MDataHandle&,  MDGContext&);

        virtual bool        setInternalValueInContext(
            const MPlug&, const MDataHandle&, MDGContext&);

        static  void*       creator();
        static  MStatus     initialize();

        static  MTypeId     id;             // The IFF type id
        static  MObject     aTransparency;

    private:
        double              fTransparency;
    };

    MObject customImagePlane::aTransparency;

    customImagePlane::customImagePlane() :
        fTransparency( 0.0 )
    {
    }

    bool
    customImagePlane::getInternalValueInContext(
        const MPlug &plug, MDataHandle &handle,  MDGContext& context )
    {
        if ( plug == aTransparency ) {
            handle.set( fTransparency );
            return true;
        }

        return MPxImagePlane::getInternalValueInContext( plug, handle, context );
    }

    bool
    customImagePlane::setInternalValueInContext(
        const MPlug &plug, const MDataHandle &handle, MDGContext &context)
    {
        if ( plug == aTransparency ) {
            fTransparency = handle.asDouble();
            setImageDirty();
            return true;
        }

        return MPxImagePlane::setInternalValueInContext( plug, handle, context );
    }

    MStatus
    customImagePlane::loadImageMap(
        const MString &fileName, int frame, MImage &image )
    {
        image.readFromFile(fileName);

        unsigned int width, height;
        image.getSize(width, height);
        unsigned int size = width * height;

        unsigned char *pixels = image.pixels();
        unsigned int i;
        for ( i = 0; i < size; i ++, pixels += 4 ) {
            pixels[3] = (unsigned char)(pixels[3] * (1.0 - fTransparency));
        }

        MPlug depthMap( thisMObject(), useDepthMap );
        bool value;
        depthMap.getValue( value );

        if ( value ) {
            float *buffer = new float[width*height];
            unsigned int c, j;
            for ( c = i = 0; i < height; i ++ ) {
                for ( j = 0; j < width; j ++, c++ ) {
                    if ( i > height/2 ) {
                        buffer[c] = -1.0f;
                    } else {
                        buffer[c] = 0.0f;
                    }
                }
            }
            image.setDepthMap( buffer, width, height );
            delete [] buffer;
        }

        return MStatus::kSuccess;
    }

    MTypeId customImagePlane::id( 0x1A19 );

    void*
    customImagePlane::creator()
    {
        return new customImagePlane;
    }

    MStatus
    customImagePlane::initialize()
    {
        MFnNumericAttribute nAttr;

        aTransparency = nAttr.create( "transparency", "tp",
                                      MFnNumericData::kDouble, 0 );
        nAttr.setStorable(true);
        nAttr.setInternal(true);
        nAttr.setMin(0.0);
        nAttr.setMax(1.0);
        nAttr.setDefault(0.0);
        nAttr.setKeyable(true);

        addAttribute( aTransparency );

        return MStatus::kSuccess;
    }

    // These methods load and unload the plugin, registerNode registers the
    // new node type with maya
    //
    MStatus initializePlugin( MObject obj )
    {
        MStatus   status;
        MFnPlugin plugin( obj, PLUGIN_COMPANY, "7.0", "Any");

        status = plugin.registerNode( "customImagePlane", customImagePlane::id,
                                      customImagePlane::creator,
                                      customImagePlane::initialize,
                                      MPxNode::kImagePlaneNode );
        if (!status) {
            status.perror("registerNode");
            return( status );
        }

        return( status );
    }

    MStatus uninitializePlugin( MObject obj)
    {
        MStatus   status;
        MFnPlugin plugin( obj );

        status = plugin.deregisterNode( customImagePlane::id );
        if (!status) {
            status.perror("deregisterNode");
            return( status );
        }

        return( status );
    }