hwUnlitShader/ShadingConnection.cpp

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// ShadingConnection.cpp

// DESCRIPTION:  This class stores useful information about
//               a shader's attribute, including what's connected upstream of it.
//               It also automatically passes through shader switches.
//
// AUTHOR: Christian Laforte
//

#include <maya/MObject.h>
#include <maya/MColor.h>
#include <maya/MString.h>
#include <maya/MStringArray.h>
#include <maya/MFnDependencyNode.h>
#include <maya/MPlug.h>
#include <maya/MPlugArray.h>

#include <assert.h>


#include "ShadingConnection.h"

ShadingConnection::ShadingConnection(MObject shaderObj, MString shapeName, MString attribute /* = "" */)
{
    // Store those input values for later use.
    this->m_shaderObj = shaderObj;
    this->m_shapeName = shapeName;

    // By default, the connection is direct until proven otherwise.
    this->m_directConnection = true;

    if (attribute != "")
        traverseAttribute(attribute);
}

ShadingConnection::TYPE ShadingConnection::traverseAttribute(MString attributeName)
{
    // Get a plug to the attribute.
    MStatus status;
    MFnDependencyNode shaderNode(m_shaderObj);

    MPlug plug = shaderNode.findPlug( attributeName, &status );
    assert(status);

    this->m_attributeName = attributeName;

    return analyzePlug(plug);
}
    
ShadingConnection::TYPE ShadingConnection::analyzePlug(MPlug plug)
{
    MStatus status;

    // Find all incoming connections.
    MPlugArray connectedElements;
    plug.connectedTo( connectedElements, true, false, &status );
    assert(status);
    
    if (connectedElements.length() == 0)
    {
        // It's a constant color... set it now and return.
        unsigned int numChildren = plug.numChildren();
        assert(numChildren == 3);

        float red, green, blue;
        plug.child(0).getValue(red);
        plug.child(1).getValue(green);
        plug.child(2).getValue(blue);

        return setConstantColor(MColor(red, green, blue, 1.0));
    }
    
    // The plug is actually connected on a different shading node.
    MObject connectedObject = connectedElements[0].node(&status);
    assert(status);

    // If this is a triple shading switch, go through it.
    if (connectedObject.hasFn(MFn::kTripleShadingSwitch))
    {
        return traverseTripleShadingSwitch(connectedObject);
    }

    // Set the object and return the appropriate type.
    return setTexture(connectedObject);
}

ShadingConnection::TYPE ShadingConnection::traverseTripleShadingSwitch(MObject connectedObject)
{           
    // The connection cannot be direct anymore.
    m_directConnection = false;
    
    MFnDependencyNode node(connectedObject);

    MStatus status;
    MPlug inputPlug = node.findPlug( "input" );
    
    unsigned int numElements = inputPlug.numElements();
    unsigned int numChildren = inputPlug.numChildren();
    
    // It is assumed that the first child of this input compound attribute is
    // a "inTexture" attribute and the the second child is the inShape attribute.
    // This assumption should always be safe, unless some drastic changes occured in the
    // implementation of the shading switches... in which case this code won't work, so
    // we would throw an exception.
    assert( numChildren >= 2); // "Abnormal hierarchy in switching node."
    
    // Go through each row of the switch table.
    for (unsigned int index = 0; index < numElements; index++)
    {
        MPlug inTexturePlug = inputPlug.elementByPhysicalIndex(index).child(0);
        MPlug inShapePlug = inputPlug.elementByPhysicalIndex(index).child(1);               

        MPlugArray inShapeConnections;
        inShapePlug.connectedTo( inShapeConnections, true, false, &status );
        
        // Check if one of the corresponding shapes matches the given shape name.
        unsigned int numCorrespondingShapes = inShapeConnections.length();
        for (unsigned int shapeNum = 0; shapeNum < numCorrespondingShapes; shapeNum++)
        {
            MObject inShapeObj = inShapeConnections[0].node(&status);
            assert(status);
            
            MFnDependencyNode inShape(inShapeObj);
            MString inShapeName = inShape.name();

            if (inShapeName == m_shapeName)
                return analyzePlug(inTexturePlug);
        }
    }

    // If there was no special case in the switch for our shape, check the default.
    MPlug defaultPlug = node.findPlug("default");
    return analyzePlug(defaultPlug);
}

ShadingConnection::TYPE ShadingConnection::type()
{
    return m_type;
}

MColor ShadingConnection::constantColor()
{
    assert(m_type == CONSTANT_COLOR);
    return m_constantColor;
}

MObject ShadingConnection::texture()
{
    assert(m_type == TEXTURE);
    return m_texture;
}

MObject ShadingConnection::shaderObj()
{
    return m_shaderObj;
}

MString ShadingConnection::shaderName()
{
    MStatus stat;
    MFnDependencyNode shaderNode(m_shaderObj, &stat);
    assert(stat);
    return shaderNode.name();
}

MString ShadingConnection::attributeName()
{
    return m_attributeName;
}

MString ShadingConnection::shapeName()
{
    return m_shapeName;
}

ShadingConnection::TYPE ShadingConnection::setConstantColor(MColor col)
{
    m_constantColor = col;
    m_type = CONSTANT_COLOR;

    // Reset m_texture to prevent misinterpretation.
    m_texture = MObject();

    return m_type;
}

ShadingConnection::TYPE ShadingConnection::setTexture(MObject texture)
{
    m_texture = texture;
    m_type = TEXTURE;

    // Reset m_color to prevent misinterpretation.
    m_constantColor = MColor();

    return m_type;
}

bool ShadingConnection::isDirectConnection()
{
    return m_directConnection;
}