Curve Output

Curves authored in Houdini are emitted on the Godot side as Path3D nodes parented under HEGoNode3D/Outputs. Each curve part becomes one Path3D with a Curve3D resource populated from the Houdini control points.

Curve Creation

Every curve primitive in the cooked HDA produces one Path3D node. In the case of polygonal (linear) curves, the control points (P) are simply added in order to the Path3D’s Curve3D.

Godot’s Curve3D cannot represent NURBS curves directly, because their control points do not necessarily lie on the curve itself. Houdini NURBS curves are therefore approximated by evaluating the curve’s basis functions, sampling points along it and adding those samples to the Curve3D. Control-point weights are not currently applied, so the result is a non-rational (B-spline) approximation of the source curve.

Godot’s Curve3D natively supports Bezier curves, so Houdini Bezier curves are output accurately with adjustable in/out control handles. Both open and closed curves are supported, with the curve’s is_closed property used to set the corresponding flag on the Curve3D.

Primitive Attributes

Curve output placement is controlled by primitive attributes:

Attribute Name	Attribute Type	Attribute Owner	Description
hego_node_path	String	Prim	Output node path/name under HEGoNode3D/Outputs. Intermediate names become Node3D containers; the last path component is the name of the Path3D itself. When missing, a default name of the form Curves/Curve3D_<type>_<index> is used.

Splitting Output into Multiple Curves

One HDA can emit many curves — assign different hego_node_path values across primitives to place them under separate Node3D containers, mirroring the pattern used for mesh output. Reusing the same path on a recook updates the existing Path3D in place rather than creating duplicates.

Fetching Curves Directly

For custom workflows, HEGoAssetNode.fetch_curves() returns the raw curve data (type, order, positions, knots, is_closed, and the requested prim/point attributes) as an Array of dictionaries, so advanced users can build their own curve resources or custom scene structures.