spatialgeometry.SceneNode

class SceneNode(pose: ndarray | SE3 = array([[1., 0., 0., 0.], [0., 1., 0., 0.], [0., 0., 1., 0.], [0., 0., 0., 1.]]), scene_parent: SceneNode | None = None, scene_children: list[SceneNode] | None = None)

Bases: object

Base class for a node in a scene graph.

Subclassed for particular shapes and provides the shape’s pose, a parent/children relationship to other nodes, and the ability to compute its pose in the world frame from the scene graph.

Parameters:

• pose – Local reference frame of this node relative to its parent in the scene graph (or the world frame if it has no parent), defaults to the identity transform.

• scene_parent – Parent node of this node in the scene graph.

• scene_children – Child nodes of this node in the scene graph.

attach(object: SceneNode) → None

Attach a child node

Parameters:

object – the node to attach as a child of this node

Seealso:

attach_to() scene_children()

attach_to(object: SceneNode) → None

Attach this node to a parent node

Parameters:

object – the node to attach this node to, this node will become a child of the parent

Seealso:

attach() scene_parent()

property scene_children: list[SceneNode]

Return the child nodes of this object in the scene graph.

Setting a new list of children updates each child’s scene_parent to this object, but does not remove this object from any previous parent’s scene_children.

This is a read/write property.

Return type:

list(SceneNode)

Seealso:

scene_parent() attach() attach_to()

property scene_parent: SceneNode | None

Return the parent node of this object in the scene graph.

Setting a new parent adds this object to the new parent’s scene_children.

This is a read/write property.

Return type:

SceneNode | None

Seealso:

scene_children() attach() attach_to()

property T: ndarray

Pose of the shape relative to its parent frame in the scene graph (or the world frame if it has no parent), as a 4x4 homogeneous transformation matrix. Set via the pose argument of the constructor.

This is a read/write property. The getter always returns a plain ndarray; the setter also accepts an SE3.

Warning

Because the getter returns an ndarray, in-place operators like shape.T *= delta do an elementwise multiply, not a pose composition, even when delta is an SE3 – use shape.T = shape.T * delta (or shape.T @= delta.A) instead.

Return type:

ndarray(4,4)

tree() → str

Render the whole tree this node lives in as indented text – walks up to the root first (the same root-finding as update()), then renders down from there, with this node marked with a trailing <== so its position in the tree is visible.

Return type:

str

tree_children() → str

Render this node’s own subtree as indented text (one repr() per line), not walking through parents – the same “not through parents” scope as _propagate_scene_children().

Nodes have no .name in this package, so each line is that node’s own repr() (type, constructor params, color, pose) – usually enough to tell siblings apart, since it’s rare for two distinct nodes to share an identical pose as well as everything else.

Return type:

str

update() → None

Recompute the world transform of every node in the scene graph this node belongs to, starting from the root and working down.

Call this after changing any node’s T/pose (or its scene_parent) – nothing propagates automatically. It doesn’t matter which node in the graph you call it on: this always walks up to the root first, then pushes fresh world transforms down through the whole tree, not just this node’s own subtree.