USD Traversal

A USD Asset is a node that uses virtual nodes to represent its content in the Rumba universe. To access these virtual nodes, we use node delegates.

Traversal of a USD asset

python

import rumba

# Retrieve the USD node delegate root
def usd_root(usd_asset):
        return usd_asset.node_delegate().find("display.output/")

# How to traverse the USD nodes
def traverse_usd_nodes(parent):
        for child in parent.children():
                print (child.path())
                traverse_usd_nodes(child)

# Get the USDAsset node
usd_asset = rumba.active_document().child("asset_name")
traverse_use_nodes(usd_root(usd_asset))

Listing all attributes of selected USD object

python

selected_nds = rumba.delegate_selection()
for nd in selected_nds:
        for attr in nd.attributes():
                # True if this attribute is overridden
                is_overridden = attr.is_overridden()
                type_name = attr.type_name()
                if type_name == "Int":
                        print(f"{attr.name()} {attr.value().as_int()}")
                if type_name == "Bool":
                        print(f"{attr.name()} {attr.value().as_bool()}")
                if type_name == "Float":
                        print(f"{attr.name()} {attr.value().as_float()}")

Listing all overridden attributes

When an attribute of an USD object inside an USD Asset is modified, it creates an override in Rumba that can later be exported as an USD Layer. Here is a snippet of code to access all the created overrides :

python

import rumba

# How to get USD overrides

# Retrieve the USD node delegate root
def usd_root(usd_asset):
        return usd_asset.node_delegate().find("display.output/")

class Override:
        """ A single override on the USD content

        path: the USD path of USD Node
        attribute: the name of the overidden attribute
        value: the new value
        """
        def __init__(self, path, attribute, value):
                self.path = path
                self.attribute = attribute
                self.value = value

def usd_overrides(usd_asset):
        """ Return all the overrides done on the USD content """
        override = usd_asset.child("override")
        override_output = override.plug("output")
        override_paths = override.plug("paths")
        value_index = 2
        result = []
        for dep_plug in override_paths.valued_dependencies():
                attribute_path = dep_plug.as_string()
                path = attribute_path.split(".")
                attribute = ".".join(path[1:])
                value = override_output.valued_dependencies()[value_index].value()
                result.append(Override(path[0], attribute, value))
                value_index += 1
        return result

def usd_attribute(usd_asset, override):
        """ Return the node delegate of an overridden object and its atribute delegate """
        nd = usd_root(usd_asset).find(override.path)
        return (nd, nd.attribute(override.attribute))

# Get the USDAsset node
usd_asset = rumba.active_document().child("Kitchen_set")

# Traverse the USD overrides
overrides = usd_overrides(usd_asset)
for o in overrides:
        value = o.value
        (nd, nd_attr) = usd_attribute(usd_asset, o)
        if value.type_name() == "M44f":
                # The overriden matrix
                override_matrix = value.as_M44d()

                # The new local matrix
                matrix = nd.matrix()

                # The new world matrix
                world_matrix = nd.world_matrix()
        elif value.type_name() == "Int":
                override_value = value.as_int()