How to get the user-defined attribute value of Alembic file in Houdini

[yaoyansi]

How to get the user-defined attribute value of Alembic file in Houdini?

Hi all,
I am new to Houdini, and I'm sorry if this question is too simple.

I use the following function to add user attributes on node:

def addAttrs():
    nodeName = '|objects:pCylinder1|objects:pCylinderShape1'
    
    # compound attribute
    cmpAttrName = 'crease__objects_cyCreaseSet0'        
    cmds.addAttr(nodeName, ln=cmpAttrName, sn=cmpAttrName,    at='compound',     readable=True, writable=True, storable=True, keyable=True, numberOfChildren=6)
    
    # child attribues
    attrName = cmpAttrName+'name'
    cmds.addAttr(nodeName, ln=attrName,    sn=attrName,  dt='string',       readable=True, writable=True, storable=True, keyable=True, parent=cmpAttrName)           
    attrName = cmpAttrName+'owner'
    cmds.addAttr(nodeName, ln=attrName,   sn=attrName,   dt='string',       readable=True, writable=True, storable=True, keyable=True, parent=cmpAttrName)
    attrName = cmpAttrName+'level'       
    cmds.addAttr(nodeName, ln=attrName,   sn=attrName,   at='float',        readable=True, writable=True, storable=True, keyable=True, parent=cmpAttrName)
    attrName = cmpAttrName+'edgecnt'      
    cmds.addAttr(nodeName, ln=attrName, sn=attrName,     at='long',         readable=True, writable=True, storable=True, keyable=True, parent=cmpAttrName)
    attrName = cmpAttrName+'edges'    
    cmds.addAttr(nodeName, ln=attrName,   sn=attrName,   dt='Int32Array',   readable=True, writable=True, storable=True, keyable=True, parent=cmpAttrName)
    attrName = cmpAttrName+'vertex'       
    cmds.addAttr(nodeName, ln=attrName,  sn=attrName,    dt='Int32Array',   readable=True, writable=True, storable=True, keyable=True, parent=cmpAttrName)     

 
    

And I export the alembic file from Maya with the following command:
cmds.AbcExport(jobArg=' -frameRange 1 2  -userAttrPrefix "crease__"    -file "test.ma.crease__.abc"')


I use abcecho command to confirm that the user-defined attributes are exported into abc file:

Object name=/objects:pCylinder1
  CompoundProperty name=.xform;schema=AbcGeom_Xform_v3
Object name=/objects:pCylinder1/objects:pCylinderShape1
  CompoundProperty name=.geom;schema=AbcGeom_PolyMesh_v1
    ScalarProperty name=.selfBnds;interpretation=box;datatype=float64_t[6];arraysize=6;numsamps=1
    ArrayProperty name=P;interpretation=point;datatype=float32_t[3];arraysize=42;numsamps=1
    ArrayProperty name=.faceIndices;interpretation=;datatype=int32_t;arraysize=200;numsamps=1
    ArrayProperty name=.faceCounts;interpretation=;datatype=int32_t;arraysize=60;numsamps=1
    CompoundProperty name=.arbGeomParams;schema=
    CompoundProperty name=.userProperties;schema=
      ScalarProperty name=crease__objects_cyCreaseSet0name;interpretation=;datatype=string;arraysize=1;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet0owner;interpretation=;datatype=string;arraysize=1;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet0level;interpretation=;datatype=float32_t;arraysize=1;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet0edgecnt;interpretation=;datatype=int32_t;arraysize=1;numsamps=1
      ArrayProperty name=crease__objects_cyCreaseSet0edges;interpretation=;datatype=int32_t;arraysize=20;numsamps=1
      ArrayProperty name=crease__objects_cyCreaseSet0vertex;interpretation=;datatype=int32_t;arraysize=40;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet1name;interpretation=;datatype=string;arraysize=1;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet1owner;interpretation=;datatype=string;arraysize=1;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet1level;interpretation=;datatype=float32_t;arraysize=1;numsamps=1
      ScalarProperty name=crease__objects_cyCreaseSet1edgecnt;interpretation=;datatype=int32_t;arraysize=1;numsamps=1
      ArrayProperty name=crease__objects_cyCreaseSet1edges;interpretation=;datatype=int32_t;arraysize=3;numsamps=1
      ArrayProperty name=crease__objects_cyCreaseSet1vertex;interpretation=;datatype=int32_t;arraysize=6;numsamps=1
    ArrayProperty name=N;interpretation=normal;datatype=float32_t[3];arraysize=200;numsamps=1

I'm going to use these attributes to control the softness of the mesh edges in rendering. But I don't know how to get these user-defined attributes in Houdini.
I use Houdini 12~14, and it seems that Houdini doesn't show the user-defined attributes by default, but I'm not sure about this.

So, my question is:
Could you tell me how to get these user-defined attributes in Houdini?

Cheers
yao



P.S.

I can access the user attributes with the following scripts:

import _alembic_hom_extensions as abc
print '------------------'
a = abc.alembicUserProperty('/test.ma.crease__.abc', '/objects:pCylinder1/objects:pCylinderShape1', 'crease__objects_cyCreaseSet0name', 1)
print a

b = abc.alembicUserProperty('/test.ma.crease__.abc', '/objects:pCylinder1/objects:pCylinderShape1', 'crease__objects_cyCreaseSet0edges', 1)
print b

c = abc.alembicUserProperty('/test.ma.crease__.abc', '/objects:pCylinder1/objects:pCylinderShape1', 'crease__objects_cyCreaseSet0vertex', 1)
print c

But, my question is:

Could I connect the user-defined attribute(source attribute) to another node's attribute(destination attribute)? I prefer this way because if the source attribute is changed the destination attribute will be changed synchronously.

 

Edited October 14, 2015 by yaoyansi

[Maurits]

In Houdini you can use the Alembic node to import the object, this on its own creates a packed primitive with no attribute data.
Then use a Convert node to convert the packed object to polygons that contain all the attribute's created earlier.
 

I only tested it using Alembic files created by Houdini but should work just fine.