Scene Building

Build and modify MuJoCo scenes from MJCF specifications. More...

Functions
bool	mj_kdl::save_model_xml (const mjModel *model, const char *path)
bool	mj_kdl::attach_to_spec (mjSpec *robot_spec, const AttachmentSpec *a)
bool	mj_kdl::build_scene (mjModel **out_model, mjData **out_data, const SceneSpec *spec)
void	mj_kdl::destroy_scene (mjModel *model, mjData *data)
bool	mj_kdl::scene_add_object (mjModel **model, mjData **data, SceneSpec *spec, const SceneObject &obj)
bool	mj_kdl::scene_remove_object (mjModel **model, mjData **data, SceneSpec *spec, const std::string &name)

Detailed Description

Build and modify MuJoCo scenes from MJCF specifications.

The primary entry point is build_scene(). Use scene_add_object() and scene_remove_object() to dynamically modify a running scene.

Function Documentation

attach_to_spec()

bool mj_kdl::attach_to_spec	(	mjSpec *	robot_spec,
		const AttachmentSpec *	a
	)

Apply one attachment to an arm spec using the MuJoCo spec API (mjs_attach). Parses a->mjcf_path, attaches its first root body under a->attach_to with the given pos/euler offset, prefixes all element names with a->prefix, and registers contact exclusions via mjs_addExclude. Can be called repeatedly to build a chain: each subsequent a->attach_to may reference any body added by prior calls.

Parameters

[in,out]	robot_spec	Accumulated robot spec to attach into.
[in]	a	Attachment; a->mjcf_path must not be null.

Returns

true on success.

build_scene()

bool mj_kdl::build_scene	(	mjModel **	out_model,
		mjData **	out_data,
		const SceneSpec *	spec
	)

Build a MuJoCo scene from one or more robots using the MuJoCo spec API. This is the primary scene-building function.

For each RobotSpec: mj_parseXML loads the root MJCF, then attach_to_spec() applies each entry in RobotSpec::attachments in order (mount, sensor, gripper, etc.), and mjs_attach places the complete robot spec at the given position. A single mj_compile produces the final model – no intermediate XML files are written.

Parameters

[out]	out_model	Newly allocated MuJoCo model; caller frees via destroy_scene().
[out]	out_data	Newly allocated MuJoCo data; caller frees via destroy_scene().
[in]	spec	Scene description: robots (with attachment chains), table, objects, timestep, gravity, floor, skybox.

Returns

true on success.

Referenced by main(), DualArmTest::SetUp(), InitTest::SetUp(), MjcfLoadTest::SetUp(), MjcfGripperTest::SetUp(), MjcfPickTest::SetUp(), MjcfPosCtrlTest::SetUp(), MjcfTrqCtrlTest::SetUp(), MjcfVelCtrlTest::SetUp(), and TableSceneTest::SetUp().

destroy_scene()

void mj_kdl::destroy_scene	(	mjModel *	model,
		mjData *	data
	)

Free a model/data pair allocated by any scene-building function.

Parameters

[in]	model	Model to free (may be null).
[in]	data	Data to free (may be null).

Referenced by main(), DualArmTest::TearDown(), InitTest::TearDown(), MjcfLoadTest::TearDown(), MjcfGripperTest::TearDown(), MjcfPickTest::TearDown(), MjcfPosCtrlTest::TearDown(), MjcfTrqCtrlTest::TearDown(), MjcfVelCtrlTest::TearDown(), and TableSceneTest::TearDown().

save_model_xml()

bool mj_kdl::save_model_xml	(	const mjModel *	model,
		const char *	path
	)

Save the compiled model to an MJCF XML file for later reloading via build_scene(). Must be called with the model returned by the most recent build_scene() call - MuJoCo only retains the last compiled model's XML internally. Typical use: build a combined scene (dual-arm, arm+gripper, ...) once, save it, then reload via build_scene() in subsequent runs to skip all build steps.

Parameters

model	Model to save; must be the most recently compiled model.
path	Output path for the MJCF XML file.

Returns

true on success.

scene_add_object()

bool mj_kdl::scene_add_object	(	mjModel **	model,
		mjData **	data,
		SceneSpec *	spec,
		const SceneObject &	obj
	)

Add an object to the scene by appending it to spec->objects and rebuilding the model. The old model/data are freed; new ones replace them. Any Robot handles sharing the old model/data become stale - call init_robot() again on the new model/data after this call.

Parameters

[in,out]	model	Current model pointer; updated to new model on success.
[in,out]	data	Current data pointer; updated to new data on success.
[in,out]	spec	Scene spec; obj is appended to spec->objects.
[in]	obj	Object to add.

Returns

true on success; model/data and spec->objects unchanged on failure.

Referenced by TEST_F().

scene_remove_object()

bool mj_kdl::scene_remove_object	(	mjModel **	model,
		mjData **	data,
		SceneSpec *	spec,
		const std::string &	name
	)

Remove a named object from the scene by erasing it from spec->objects and rebuilding the model. The old model/data are freed; new ones replace them. Any Robot handles sharing the old model/data become stale - call init_robot() again on the new model/data after this call.

Parameters

[in,out]	model	Current model pointer; updated to new model on success.
[in,out]	data	Current data pointer; updated to new data on success.
[in,out]	spec	Scene spec; named object removed from spec->objects.
[in]	name	Name of the object to remove.

Returns

true on success; false if name not found or rebuild fails.

Referenced by TEST_F().