Do not overwrite existing parent frames for worldbody elements when attaching an mjSpec to a frame or a site.

PiperOrigin-RevId: 737662046
Change-Id: I7028c21c803c01845ae1d53cb476f7b3df172313

doc/APIreference/functions.rst

@@ -4202,6 +4202,15 @@ Find child body by name.
 
 Get parent body.
 
+.. _mjs_getFrame:
+
+`mjs_getFrame <#mjs_getFrame>`__
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. mujoco-include:: mjs_getFrame
+
+Get parent frame.
+
 .. _mjs_findFrame:
 
 `mjs_findFrame <#mjs_findFrame>`__

doc/changelog.rst

@@ -15,6 +15,8 @@ Bug fixes
 ^^^^^^^^^
 - :ref:`mj_jacDot` was missing a term that accounts for the motion of the point with respect to
   which the Jacobian is computed, now fixed.
+- Fixed a bug that caused the parent frame of elements in the child worldbody to be incorrectly set when attaching an
+  mjSpec to a frame or a site.
 
 Version 3.3.0 (Feb 26, 2025)
 ----------------------------

doc/includes/references.h

@@ -3649,6 +3649,7 @@ mjsBody* mjs_findBody(mjSpec* s, const char* name);
 mjsElement* mjs_findElement(mjSpec* s, mjtObj type, const char* name);
 mjsBody* mjs_findChild(mjsBody* body, const char* name);
 mjsBody* mjs_getParent(mjsElement* element);
+mjsFrame* mjs_getFrame(mjsElement* element);
 mjsFrame* mjs_findFrame(mjSpec* s, const char* name);
 mjsDefault* mjs_getDefault(mjsElement* element);
 const mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);