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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