Hi Enrico,
actually you can access to all geometry data also from a MPxNode, maybe is
also more easy.
In my opinion if you don't need build a deformer, is better use a node.
A rivet node, is also quite simple to do, you need just few geometry datas
so, my suggestion it's go with a node =)
For access to all mesh functions you need get an handle to your MObject, in
my case aInMesh:
[CODE]
# inputMesh
aInMesh = OpenMaya.MObject()
[/CODE]
For example this is my compute node:
[CODE]
# Node compute
def compute(self, plug, data):
thisNode = uberRivetNode.thisMObject(self)
inputMeshPlug = OpenMaya.MPlug(thisNode, uberRivetNode.aInMesh)
if not inputMeshPlug.isConnected():
return OpenMaya.kNotImplemented
...
...
# Get handle to inputMesh
inputMesh = data.inputValue(uberRivetNode.aInMesh).asMesh()
[/CODE]
[CODE]
# Get handle to inputMesh
inputMesh = data.inputValue(uberRivetNode.aInMesh).asMesh()
[/CODE]
And after you can get mesh functions with:
[CODE]
fnMesh = OpenMaya.MFnMesh(inputMesh)
[/CODE]
If you have any questions, just ask
Cheers
Leonardo
2014-07-30 1:21 GMT+02:00 Enrico Losavio <[email protected]>:
> Hi everyone!
>
> I'm trying to write a sort of River node, but I ran into some difficulties
> (obviously :) ) and any help would be greatly appreciated!
>
> Basically i want a DG node that can
>
> - accept geometry as an input
> - retrieve mesh information
> - make up his own calculations based on the mesh information and a few
> custom attributes
> - have an array of MPoints (or k3Double i guess) as output to be piped
> into each locator
> - have the output updated every time an attribute or the mesh itself
> changes
>
> As far as I know, the MPxDeformerNode is the only way to access the
> geometry data. But I don't want to deform the mesh, just query information.
> And yet I don't fully understand how the push-pull mechanism works in this
> case. In a custom DG node i would use the "if plug == attribute" to force
> the evaluation, but in this case...?
> I've already jot down the basic structure for the node, but it doesn't
> work as it should.
> In Maya I loaded the plugin, applied the deformer to a simple cube, and
> fed each value of the array into the Translate attribute of specifically
> created locators (that thus went in the correct position, one on each
> vertex)
> If I tweak the mesh, the locators remain in the same position, don't
> follow the vertices. If I change the value of the positionOffset attribute,
> nothing happens.
> But I noticed that if i tweak the mesh and then change the value of the
> attribute, the position of all the locators suddenly updates as though the
> mesh is read properly, but the positionOffset value remains the previous
> one.
>
> Here's a simplified version of the code I wrote...:
>
> class AttachToMesh(OMMPx.MPxDeformerNode):
>
>
> mObj_positionOffset = OM.MObject()
> mObj_outPosition = OM.MObject()
>
>
> def __init__(self):
> OMMPx.MPxDeformerNode.__init__(self)
>
>
> def deform(self, dataBlock, geoIterator, matrix, geometryIndex):
>
> # RETRIEVE GEOMETRY DATA
> input = OMMPx.cvar.MPxDeformerNode_input
> dataHandleInputArray = dataBlock.outputArrayValue(input)
> dataHandleInputArray.jumpToElement(geometryIndex)
> dataHandleInputElement = dataHandleInputArray.outputValue()
>
> inputGeom = OMMPx.cvar.MPxDeformerNode_inputGeom
> dataHandleInputGeom = dataHandleInputElement.child(inputGeom)
> inMesh = dataHandleInputGeom.asMesh()
>
>
> # POSITION OFFSET
> dataHandlePositionOffset = dataBlock.inputValue(AttachToMesh.
> mObj_positionOffset)
> positionOffsetValue = dataHandlePositionOffset.asFloat()
>
> # OUT POSITION
> dataHandleArrayOutPosition = dataBlock.outputArrayValue(
> AttachToMesh.mObj_outPosition)
> dataBuilderOutPosition = dataHandleArrayOutPosition.builder()
>
> vertexPosition = OM.MPoint()
> mFnMesh = OM.MFnMesh(inMesh)
>
> normals = OM.MFloatVectorArray()
> mFnMesh.getVertexNormals(False, normals)
>
>
> while not geoIterator.isDone():
>
>
> vertexPosition.x = geoIterator.position().x + ( normals[
> geoIterator.index()].x * positionOffsetValue )
> vertexPosition.y = geoIterator.position().y + ( normals[
> geoIterator.index()].y * positionOffsetValue )
> vertexPosition.z = geoIterator.position().z + ( normals[
> geoIterator.index()].z * positionOffsetValue )
>
> dataHandleOutPosition = dataBuilderOutPosition.addElement(
> geoIterator.index())
> dataHandleOutPosition.set3Double(vertexPosition.x,
> vertexPosition.y, vertexPosition.z)
>
> geoIterator.next()
>
> dataHandleArrayOutPosition.set(dataBuilderOutPosition)
>
> #here I'm not sure which setClean function I'm supposed to use...
> in this case I chose dataBlock.setClean
> #dataHandleArrayOutPosition.setAllClean()
>
> dataBlock.setClean(AttachToMesh.mObj_outPosition)
>
>
> def nodeInitializer():
> mFnAttr = OM.MFnNumericAttribute()
>
>
> AttachToMesh.mObj_positionOffset = mFnAttr.create("positionOffset",
> "posOff", OM.MFnNumericData.kFloat, 0.0)
> mFnAttr.setKeyable(1)
>
> AttachToMesh.mObj_outPosition = mFnAttr.create("outPosition", "outPos"
> , OM.MFnNumericData.k3Double, 0.0)
> mFnAttr.setKeyable(0)
> mFnAttr.setWritable(0)
> mFnAttr.setArray(1)
> mFnAttr.setUsesArrayDataBuilder(1)
>
> AttachToMesh.addAttribute(AttachToMesh.mObj_outPosition)
>
> AttachToMesh.attributeAffects(AttachToMesh.mObj_positionOffset,
> AttachToMesh.mObj_outPosition)
>
>
>
> Thank you in advance for any reply!!
>
>
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