A.2 Build Animation Graph

In this tutorial, we are going to show how to build your own Animation graph to control character animation.

First, drag character and animation file into Omniverse

Note

(Optional) We may apply Python code for import USD files (see more: Stage)

character_path = "/World/character"
anim_path = "/World/character_anim_clip"

character_usd = "E:/researches/VRKitchen2.0-Tutorial/asset/mixamo/peasant_girl_converted.usd"
anim_usd = "E:/researches/VRKitchen2.0-Tutorial/asset/mixamo/silly_dancing_converted.usd"

prim = self.stage.GetPrimAtPath(character_path)
if not prim.IsValid():
    prim = self.stage.DefinePrim(character_path)

success_bool = prim.GetReferences().AddReference(character_usd)
assert success_bool

prim = self.stage.GetPrimAtPath(anim_path)
if not prim.IsValid():
    prim = self.stage.DefinePrim(anim_path)

success_bool = prim.GetReferences().AddReference(anim_usd)

Create a new animation graph and assign skeleton:

Note

(Optional) We may apply Python code handle animation graph (see more: Animation Graph)

anim_graph_path = "/World/AnimationGraph"
skeleton_path = "/World/character/Hips0/Skeleton"

### anim_graph = AnimGraphSchemaTools.createAnimationGraph(stage, Sdf.Path("/World/AnimationGraph"))
omni.kit.commands.execute("CreateAnimationGraphCommand", \
    path=Sdf.Path(anim_graph_path), skeleton_path=Sdf.Path(skeleton_path))

Apply the animation to the skeleton root:

skel_root_path = "/World/character/Hips0/" #(e.g. Hips0 for "/World/character/Hips0/Skeleton")
omni.kit.commands.execute("ApplyAnimationGraphAPICommand", \
    paths=[Sdf.Path(skel_root_path)], animation_graph_path=Sdf.Path(anim_graph_path))

Possibly need to clean the original clip:

skeleton_prim = self.stage.GetPrimAtPath(skeleton_path)
skeleton_bindingAPI = UsdSkel.BindingAPI(skeleton_prim)
skeleton_bindingAPI.GetAnimationSourceRel().SetTargets([])

Create animation clip node:

# create
omni.kit.commands.execute(
    'CreatePrimCommand',
    prim_type="AnimationClip",
    prim_path="/World/AnimationGraph/Animation",
    select_new_prim=True,
)

Add animation clip target source:

animclip_prim = self.stage.GetPrimAtPath("/World/AnimationGraph/Animation")
# animclip_bindingAPI = UsdSkel.BindingAPI(animclip_prim)

anim_clip = AnimGraphSchema.AnimationClip(animclip_prim)
source_rel = anim_clip.GetInputsAnimationSourceRel()

omni.kit.commands.execute(
    'omni.anim.graph.ui.scripts.command.SetRelationshipTargetsCommand',
    relationship=source_rel,
    targets=[Sdf.Path("/World/character_anim_clip/Hips0/mixamo_com")]
)

Finally, connect connect node:

Warning

The following Python code may cause errors

First, modify the original code in omni.anim.graph.ui.scripts.extension to make graph manager trackable

# from line 13 to 16
class PublicExtension(omni.ext.IExt):
    GRAPH_MANAGER = AnimationGraphManager()
    def on_startup(self):
        self._graph_manager = PublicExtension.GRAPH_MANAGER #AnimationGraphManager()
# ....

Then, connect nodes from scripts

self._usd_context = omni.usd.get_context()
# omni.usd.get_context().open_stage_async(path)
stage = self._usd_context.get_stage()

from omni.anim.graph.ui.scripts.extension import PublicExtension

graph_manager = PublicExtension.GRAPH_MANAGER
# print("graph manager dict", graph_manager._node_graph_dict)

from pxr import Sdf
node_graph = graph_manager.get_node_graph(Sdf.Path("/World/AnimationGraph"))
# print("node_graph: ", node_graph._path_to_node)
# node_graph._on_create_node("/World/AnimationGraph/Animation")

anim_clip_node = node_graph._path_to_node.get(Sdf.Path("/World/AnimationGraph/Animation"))
root_node = node_graph._path_to_node.get(Sdf.Path("/World/AnimationGraph"))

root_input_port = root_node.ports[0]
#print("root ports", root_input_port.kind, root_input_port.rel)

output_port = anim_clip_node.output
# print("anim port", output_port)

node_graph.create_connection(output_port,root_input_port)

Now, the animaion is here: