Ramp Attributes

[tshaynes]

I have written a plugin that creates several Maya nodes. For one of the node attributes I would like to use a Ramp Attribute (e.g. like the "Clump Width Scale" attribute in the hairSystem shape node). Can someone point me to documentation or show me how to implement this? I'd like the cool curve shape editing GUI that I see for the hairSystem node in the attribute editor too.

Thanks much

Tim
(I'm using Maya Unlimited 6.0)

[rob-bateman]

there is an example in the maya 7 devkit, otherwise i have an example on my website in the maya API section : http://robthebloke.org

[tshaynes]

Thank you so much! I dont have Maya 7 (I'm still using 6.0), but with only some minor tweaking I was able to get it going for my case using the example at your web site.

The only difference I would recommend for others using ramp attributes is to set some default values in the template code to avoid an error message during node creation.

Modified code snippet attribute editor template:

global proc AEGraphNodeTemplate( string $nodeName )
{
editorTemplate -beginScrollLayout;
editorTemplate -beginLayout "My Graph Node Attributes" -collapse 0;
AEaddRampControl "graph" ;
editorTemplate -endLayout;
AEdependNodeTemplate $nodeName;
editorTemplate -addExtraControls;
editorTemplate -endScrollLayout;
setAttr ($nodeName + ".graph[0].graph_FloatValue") 1.0;
setAttr ($nodeName + ".graph[0].graph_Position") 0.0;
setAttr ($nodeName + ".graph[0].graph_Interp") 1;
}

THANKS AGAIN Rob !!!

~Tim

[tshaynes]

I have the ramp attribute set up and working in the attribute editor of my node, but now how do I access the ramp data from within the compute method? (In the example at your web site you set up the ramp attribute but dont use it)

much thanks-

~Tim

[andersegleus]

Yeah, I'd also very much like to know how to get output values from a ramp attribute in the compute method in maya 7. I understand you can use MRampAttribute::getValueAtPosition to get the output data, but I don't understand how to construct the MRampAttribute object to attach the getValueAtPosition function to. With basic attributes you get the handle and convert it to something meaningful using MDataHandle's asFloat function for instance, but you can't do this with ramps.

[andersegleus]

Well, I'm pretty much a newbe with the API, so this solution may be really crappy. What I did was use MPxNode:: thisMObject to access the ramp attribute from within the compute method. It works, but I don't know if it's the "proper" way of doing it, since the docs stress that you should get data from plugs using handles. So maybe it's a really slow method (the node just has one computation per update, so It's hard to see if it's fast or not - for that I'd have to test it on a shading node or make a loop in this testnode which uses the getValueAtPosition method many many times during the compute method). Does anyone have any ideas wether this is the proper way of doing it?

Anyway, here's a modified version of the exampleRampAttrNode where it's used (just exchange the original code in exampleMRampAttribute.cpp with this and compile).

CODE
#include

#include
#include
#include
#include
#include
#include
#include
#include
#include

class exampleRampAttrNode : public MPxNode
{
public:
    exampleRampAttrNode() {};
    virtual        ~exampleRampAttrNode() {};
    static  void   *creator();
    static  MStatus initialize();
    virtual MStatus compute(const MPlug &plug, MDataBlock  &dataBlock);

    static MObject aRamp;
    static MObject aInput;         // The input value.
    static MObject aOutput;        // The output value.
    static MTypeId  id;

};

MTypeId exampleRampAttrNode::id( 0x81027 );

MObject exampleRampAttrNode::aRamp;
MObject exampleRampAttrNode::aInput;        
MObject exampleRampAttrNode::aOutput;      

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

MStatus exampleRampAttrNode::initialize()
{
    MFnNumericAttribute nAttr;
    MStatus stat;

    MString curveRamp("curveRamp");
    MString cvr("cvr");

    aRamp = MRampAttribute::createCurveRamp(curveRamp, cvr);

    aInput = nAttr.create( "input", "in", MFnNumericData::kFloat, 0.0 );

    aOutput = nAttr.create( "output", "out", MFnNumericData::kFloat, 0.0 );
    nAttr.setWritable(false);
    nAttr.setStorable(false);

    stat = addAttribute(aRamp);
    if(!stat)
    {
        cout << "ERROR in adding curveRamp Attribute!\n";
    }

    stat = addAttribute( aInput );
        if (!stat) { stat.perror("addAttribute"); return stat;}
    stat = addAttribute( aOutput );
        if (!stat) { stat.perror("addAttribute"); return stat;}

    stat = attributeAffects( aInput, aOutput );
        if (!stat) { stat.perror("attributeAffects"); return stat;}
    stat = attributeAffects( aRamp, aOutput );
        if (!stat) { stat.perror("attributeAffects"); return stat;}

    return stat;
}

MStatus exampleRampAttrNode::compute( const MPlug &plug, MDataBlock  &dataBlock )
{
    MStatus returnStatus;
    if( plug == aOutput )
    {
        MDataHandle inputData = dataBlock.inputValue( aInput, &returnStatus );
        if( returnStatus != MS::kSuccess )
            cerr << "ERROR getting data" << endl;
//        MDataHandle hRamp = dataBlock.inputValue( aRamp, &returnStatus );
//        if( returnStatus != MS::kSuccess )
//            cerr << "ERROR getting data" << endl;
        MObject thisNode = thisMObject();
        MRampAttribute ramp (thisNode, aRamp, &returnStatus);
        if( returnStatus != MS::kSuccess )
            cerr << "ERROR getting data" << endl;

        float rampOut = -1.0;
        float position = inputData.asFloat();

        ramp.getValueAtPosition(position, rampOut, &returnStatus);

        MDataHandle outputHandle = dataBlock.outputValue( exampleRampAttrNode::aOutput );
        outputHandle.set( rampOut );
        dataBlock.setClean(plug);

    } else {
        return MS::kUnknownParameter;
    }

    return MS::kSuccess;}

MStatus initializePlugin(MObject obj)
{
    MStatus   status;
    MFnPlugin plugin(obj, "Alias - Example", "7.0", "Any");

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

    return status;
}

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

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

    return status;
}

[mfiorilli]

It's weird... I've been trying your code and many more examples about the ramp attributes but in the attribute editor, it gives me a button <> and when I click on it, it adds these inputs to the node:

Curve Ramp0 (FLOAT) (FLOAT) (garbage icon)
Curve Ramp1 (FLOAT) (FLOAT) (garbage icon)
Curve Ramp2 (FLOAT) (FLOAT) (garbage icon)
Curve Ramp... (FLOAT) (FLOAT) (garbage icon)

it's supposed to give a ramp graphic.. not this. I don't understand.

I'm using maya 2009