Deformer question - iterating the faces

[kelly-shear]

Hi.
I want to write a deformer and I need to iterate through all the faces of my shape.
As far as i understood the deform function get block which contain all the data and iterator which will iterate through all the vertices in the shape. How can i get the faces from the block and then iterate them using a MItMeshPolygon iterator?
Is there a simpler solutions? 
Thanks.

[user_deleted]

try this:

MStatus myNode::deform( MDataBlock& block, MItGeometry &iter, const MMatrix &localToWorld, unsigned int geomIndex)
{
    //TRYING TO GET INPUT MODEL    
    MStatus stat;
    MArrayDataHandle hArrayInput= block.inputArrayValue(input, &stat);
    hArrayInput.jumpToElement(geomIndex);
    MDataHandle hInput= hArrayInput.inputValue(&stat).child(inputGeom);

    if (hInput.type() == MFnData::kMesh) {
    MItMeshPolygon faceIterator( hInput.asMesh() )
    // ... rest of code
    }
}

But don't bet any money on this, I ripped it out of some old code, not sure it works :]

[kelly-shear]

Hi. what is it the input parameter you use in the line:
MArrayDataHandle hArrayInput= block.inputArrayValue(input, &stat).

Does anybody know how to obtain the MObject inside a deformer? 

[joojaa]

Does anybody know how to obtain the MObject inside a deformer?

Well simpy put this is something that should be forbidden, its possible tough*, but VERY convoluted and is of no paricular use except professional suicide.

• did it once, this is one of those things whhere: "if you must ask your not up to the job" , holds true. Crashed maya about 30 times, and caused all other things to stop working.

[pz99]

A code snippet showing how to get at the MObject-- for instance to get at face or ordering info in the mesh-- is here, courtesy of Chad Vernon:

http://www.chadvernon.com/blog/resources/maya-api-programming/deformers/getting-the-input-geometry-mobject/

As Chad says, you have to be cautious to avoid triggering spurious reevaluations.  That's why he uses the outputValue instead of the inputValue to get to the mesh.

(Ogre's code above is nearly identical and I think would also work, but as it uses the inputValue, it risks triggering Maya to reevaluate the input mesh before giving it to you.  So I'd use the outputValue instead as in Chad's example.)

PS, the "input" MObject you were asking about is just the input attribute for the deformer.  See the MPxDeformerNode doc page:
http://download.autodesk.com/us/maya/2011help/API/class\_m\_px\_deformer\_node.html