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Sdformat -> mjcf: Fix pose for links in child models #122

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Merged
azeey merged 2 commits into from
Feb 18, 2026
Merged

Sdformat -> mjcf: Fix pose for links in child models #122

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6b54b99
Add rotation in nested model test cases
shameekganguly Feb 17, 2026
b65fff5
Fixed lint errors
shameekganguly Feb 18, 2026
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3 changes: 0 additions & 3 deletions sdformat_mjcf/src/sdformat_mjcf/sdformat_to_mjcf/converters/model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -42,9 +42,6 @@ def add_model(mjcf_root, model):
model_pose = graph_resolver.resolve_pose(model.semantic_pose())

def convert_node(body, node, link_pose):
# A node may be assigned a scoped name if it belongs to a child model
# for disambiguation. In this case, use the scoped name for the link
# body.
child_body = add_link(body, node.link, node.parent_node.scoped_name,
link_pose, node.scoped_name)

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4 changes: 2 additions & 2 deletions sdformat_mjcf/src/sdformat_mjcf/sdformat_to_mjcf/sdf_kinematics.py
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Expand Up @@ -54,7 +54,7 @@ def __init__(self, link, parent=None, joint=FreeJoint()):
# connected to the world link with a free joint.
self.resolved_pose = Pose3d()

# Scoped name assigned for child model links
# The scoped name of the link relative to the kinematic hierarchy root.
self.scoped_name = None

def __repr__(self):
Expand Down Expand Up @@ -114,7 +114,7 @@ def __init__(self, model):
child_model_pose = su.graph_resolver.resolve_pose(
child_model.semantic_pose())
for cn in child_kh.world_node.child_nodes:
cn.resolved_pose *= child_model_pose
cn.resolved_pose = child_model_pose * cn.resolved_pose
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@azeey azeey Feb 18, 2026

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Oops. Thanks for catching this!

# Removing the child node from child_kh.world_node is
# unnecessary and dangerous since it affects the iterable.
self.world_node.add_child(cn, cn.joint)
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17 changes: 10 additions & 7 deletions sdformat_mjcf/tests/sdformat_to_mjcf/test_add_model.py
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Expand Up @@ -208,9 +208,9 @@ def test_nested_model_fixed_joint(self):
</collision>
</link>
<model name="modelB">
<pose>0 1 0 0 0 0</pose>
<pose>0 1 0 0 0 1.5707</pose>
<link name="linkA">
<pose>0 1 0 0 0 0</pose>
<pose>0 1 0 1.5707 0 0</pose>
<collision name="c1">
<geometry>
<sphere><radius>2</radius></sphere>
Expand Down Expand Up @@ -244,7 +244,8 @@ def test_nested_model_fixed_joint(self):
_resolveTo="modelB::linkA")
modelB_linkA_expected_pos = su.vec3d_to_list(
sdf_linkA_pose.inverse().pos())
assert_allclose(modelB_linkA_expected_pos, mj_modelB_linkA.pos)
assert_allclose(
modelB_linkA_expected_pos, mj_modelB_linkA.pos, atol=1e-10)

def test_nested_model_multi_level(self):
test_model_sdf = """
Expand Down Expand Up @@ -289,9 +290,9 @@ def test_nested_model_fixed_joint_with_nested_parent_link(self):
</collision>
</link>
<model name="modelB">
<pose>0 1 0 0 0 0</pose>
<pose>0 1 0 0 0 1.5707</pose>
<link name="linkA">
<pose>0 10 0 0 0 0</pose>
<pose>0 10 0 1.5707 0 0</pose>
<collision name="c2">
<geometry>
<sphere><radius>2</radius></sphere>
Expand Down Expand Up @@ -329,14 +330,16 @@ def test_nested_model_fixed_joint_with_nested_parent_link(self):
modelB_linkA_expected_pos = su.vec3d_to_list(
(sdf_modelA.raw_pose() * sdf_modelB_linkA_pose).pos()
)
assert_allclose(modelB_linkA_expected_pos, mj_modelB_linkA.pos)
assert_allclose(
modelB_linkA_expected_pos, mj_modelB_linkA.pos, atol=1e-10)

# Verify that the right pos was set for (modelA::)linkA
sdf_linkA = sdf_modelA.link_by_name("linkA")
sdf_linkA_pose = sdf_linkA.semantic_pose().resolve(
_resolveTo="modelB::linkA")
modelA_linkA_expected_pos = su.vec3d_to_list(sdf_linkA_pose.pos())
assert_allclose(modelA_linkA_expected_pos, mj_modelA_linkA.pos)
assert_allclose(
modelA_linkA_expected_pos, mj_modelA_linkA.pos, atol=1e-10)


if __name__ == "__main__":
Expand Down