Constants which are powers of 2. They are used as bitmasks for the field ``disableflags`` of :ref:`mjOption`.
At runtime this field is ``m->opt.disableflags``. The number of these constants is given by ``mjNDISABLE`` which is
also the length of the global string array :ref:`mjDISABLESTRING` with text descriptions of these flags.

.. mujoco-include:: mjtDisableBit


.. _mjtEnableBit:

mjtEnableBit
~~~~~~~~~~~~

Constants which are powers of 2. They are used as bitmasks for the field ``enableflags`` of :ref:`mjOption`.
At runtime this field is ``m->opt.enableflags``. The number of these constants is given by ``mjNENABLE`` which is also
the length of the global string array :ref:`mjENABLESTRING` with text descriptions of these flags.

.. mujoco-include:: mjtEnableBit


.. _mjtJoint:

mjtJoint
~~~~~~~~

Primitive joint types. These values are used in ``m->jnt_type``. The numbers in the comments indicate how many
positional coordinates each joint type has. Note that ball joints and rotational components of free joints are
represented as unit quaternions - which have 4 positional coordinates but 3 degrees of freedom each.

.. mujoco-include:: mjtJoint


.. _mjtGeom:

mjtGeom
~~~~~~~

Geometric types supported by MuJoCo. The first group are "official" geom types that can be used in the model. The
second group are geom types that cannot be used in the model but are used by the visualizer to add decorative
elements. These values are used in ``m->geom_type`` and ``m->site_type``.

.. mujoco-include:: mjtGeom


.. _mjtProjection:

mjtProjection

Dynamic modes for cameras and lights, specifying how the camera/light position and orientation are computed. These
values are used in ``m->cam_mode`` and ``m->light_mode``.

.. mujoco-include:: mjtCamLight


.. _mjtLightType:

mjtLightType

Texture types, specifying how the texture will be mapped. These values are used in ``m->tex_type``.

.. mujoco-include:: mjtTexture


.. _mjtTextureRole:

mjtTextureRole

Type of color space encoding for textures.

.. mujoco-include:: mjtColorSpace


.. _mjtIntegrator:

mjtIntegrator

Available friction cone types. These values are used in ``m->opt.cone``.

.. mujoco-include:: mjtCone

.. _mjtJacobian:

mjtJacobian

Available constraint solver algorithms. These values are used in ``m->opt.solver``.

.. mujoco-include:: mjtSolver


.. _mjtEq:

mjtEq
~~~~~

Equality constraint types. These values are used in ``m->eq_type``.

.. mujoco-include:: mjtEq


.. _mjtWrap:

mjtWrap
~~~~~~~

Tendon wrapping object types. These values are used in ``m->wrap_type``.

.. mujoco-include:: mjtWrap


.. _mjtTrn:

mjtTrn
~~~~~~

Actuator transmission types. These values are used in ``m->actuator_trntype``.

.. mujoco-include:: mjtTrn


.. _mjtDyn:

mjtDyn
~~~~~~

Actuator dynamics types. These values are used in ``m->actuator_dyntype``.

.. mujoco-include:: mjtDyn


.. _mjtGain:

mjtGain
~~~~~~~

Actuator gain types. These values are used in ``m->actuator_gaintype``.

.. mujoco-include:: mjtGain


.. _mjtBias:

mjtBias
~~~~~~~

Actuator bias types. These values are used in ``m->actuator_biastype``.

.. mujoco-include:: mjtBias


.. _mjtObj:

mjtObj
~~~~~~

MuJoCo object types. These are used, for example, in the support functions :ref:`mj_name2id` and
:ref:`mj_id2name` to convert between object names and integer ids.

.. mujoco-include:: mjtObj


.. _mjtSensor:

mjtSensor

These are the compute stages for the skipstage parameters of :ref:`mj_forwardSkip` and
:ref:`mj_inverseSkip`.

.. mujoco-include:: mjtStage


.. _mjtDataType:

mjtDataType

Types of data fields returned by contact sensors.

.. mujoco-include:: mjtConDataField


.. _mjtRayDataField:

mjtRayDataField

Camera output type bitflags. These are used in ``m->cam_output``.

.. mujoco-include:: mjtCamOutBit


.. _mjtSameFrame:

mjtSameFrame

Sleep policy associated with a tree. The compiler automatically chooses between ``NEVER`` and ``ALLOWED``, but the user
can override this choice. Only the user can set the ``INIT`` policy (initialized as asleep).

.. mujoco-include:: mjtSleepPolicy


.. _mjtLRMode:

mjtLRMode
~~~~~~~~~

Mode for actuator length range computation. Used in ``mjLROpt.mode``.

.. mujoco-include:: mjtLRMode


.. _mjtFlexSelf:

mjtFlexSelf
~~~~~~~~~~~~

Types of flex self-collisions midphase.

.. mujoco-include:: mjtFlexSelf


.. _mjtSDFType:

mjtSDFType
~~~~~~~~~~~

Formulas used to combine SDFs when calling mjc_distance and mjc_gradient.

.. mujoco-include:: mjtSDFType


.. _tyDataEnums:

Data
^^^^

The enums below are defined in `mjdata.h <https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjdata.h>`__.



.. _mjtState:

mjtState
~~~~~~~~

State component elements as integer bitflags and several convenient combinations of these flags. Used by
:ref:`mj_getState`, :ref:`mj_setState` and :ref:`mj_stateSize`.

.. mujoco-include:: mjtState


.. _mjtConstraint:

mjtConstraint
~~~~~~~~~~~~~

Constraint types. These values are not used in mjModel, but are used in the mjData field ``d->efc_type`` when the list
of active constraints is constructed at each simulation time step.

.. mujoco-include:: mjtConstraint


.. _mjtConstraintState:

mjtConstraintState

Warning types. The number of warning types is given by ``mjNWARNING`` which is also the length of the array
``mjData.warning``.

.. mujoco-include:: mjtWarning


.. _mjtTimer:

mjtTimer
~~~~~~~~

Timer types. The number of timer types is given by ``mjNTIMER`` which is also the length of the array
``mjData.timer``, as well as the length of the string array :ref:`mjTIMERSTRING` with timer names.

.. mujoco-include:: mjtTimer


.. _mjtSleepState:

mjtSleepState

These are the available categories of geoms in the abstract visualizer. The bitmask can be used in the function
:ref:`mjr_render` to specify which categories should be rendered.

.. mujoco-include:: mjtCatBit


.. _mjtMouse:

mjtMouse
~~~~~~~~

These are the mouse actions that the abstract visualizer recognizes. It is up to the user to intercept mouse events
and translate them into these actions, as illustrated in :ref:`simulate.cc <saSimulate>`.

.. mujoco-include:: mjtMouse


.. _mjtPertBit:

mjtPertBit

These are the possible camera types, used in ``mjvCamera.type``.

.. mujoco-include:: mjtCamera


.. _mjtLabel:

mjtLabel
~~~~~~~~

These are the abstract visualization elements that can have text labels. Used in ``mjvOption.label``.

.. mujoco-include:: mjtLabel


.. _mjtFrame:

mjtFrame
~~~~~~~~

These are the MuJoCo objects whose spatial frames can be rendered. Used in ``mjvOption.frame``.

.. mujoco-include:: mjtFrame


.. _mjtVisFlag:

mjtVisFlag

These are indices in the array ``mjvScene.flags``, whose elements enable/disable OpenGL rendering effects.

.. mujoco-include:: mjtRndFlag


.. _mjtStereo:

mjtStereo
~~~~~~~~~

These are the possible stereo rendering types. They are used in ``mjvScene.stereo``.

.. mujoco-include:: mjtStereo



.. _tyRenderEnums:

Rendering
^^^^^^^^^

The enums below are defined in `mjrender.h <https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjrender.h>`__.


.. _mjtGridPos:

mjtGridPos

These are the possible framebuffers. They are used as an argument to the function :ref:`mjr_setBuffer`.

.. mujoco-include:: mjtFramebuffer


.. _mjtDepthMap:

mjtDepthMap
~~~~~~~~~~~

These are the depth mapping options. They are used as a value for the ``readPixelDepth`` attribute of the
:ref:`mjrContext` struct, to control how the depth returned by :ref:`mjr_readPixels` is mapped from
``znear`` to ``zfar``.

.. mujoco-include:: mjtDepthMap


.. _mjtFontScale:

mjtFontScale
~~~~~~~~~~~~

These are the possible font sizes. The fonts are predefined bitmaps stored in the dynamic library at three different
sizes.

.. mujoco-include:: mjtFontScale


.. _mjtFont:

mjtFont
~~~~~~~

These are the possible font types.

.. mujoco-include:: mjtFont


.. _tyUIEnums:

User Interface
^^^^^^^^^^^^^^

The enums below are defined in `mjui.h <https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjui.h>`__.


.. _mjtButton:

mjtButton
~~~~~~~~~

Mouse button IDs used in the UI framework.

.. mujoco-include:: mjtButton


.. _mjtEvent:

mjtEvent
~~~~~~~~

Event types used in the UI framework.

.. mujoco-include:: mjtEvent


.. _mjtItem:

mjtItem
~~~~~~~

Item types used in the UI framework.

.. mujoco-include:: mjtItem


.. _mjtSection:

mjtSection
~~~~~~~~~~

State of a UI section.

.. mujoco-include:: mjtSection



.. _tySpecEnums:

Spec
^^^^

The enums below are defined in `mjspec.h <https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjspec.h>`__.

.. _mjtGeomInertia:

mjtGeomInertia

Type of built-in procedural texture.

.. mujoco-include:: mjtBuiltin

.. _mjtMark:

mjtMark
~~~~~~~

Mark type for procedural textures.

.. mujoco-include:: mjtMark

.. _mjtLimited:

mjtLimited

Whether to align free joints with the inertial frame.

.. mujoco-include:: mjtAlignFree

.. _mjtInertiaFromGeom:

mjtInertiaFromGeom

Type of orientation specifier.

.. mujoco-include:: mjtOrientation

.. _mjtMeshInertia:

mjtMeshInertia

Type of built-in procedural mesh.

.. mujoco-include:: mjtMeshBuiltin


.. _tyPluginEnums:

Plugins
^^^^^^^

The enums below are defined in `mjplugin.h <https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjplugin.h>`__.
See :ref:`exPlugin` for details.


.. _mjtPluginCapabilityBit:

mjtPluginCapabilityBit

This is the data structure with abstract visualization options. It corresponds to the MJCF element
:ref:`visual <visual>`. One instance of it is embedded in mjModel.

.. mujoco-include:: mjVisual


.. _mjStatistic:

mjStatistic

This is the data structure holding information about one contact. ``mjData.contact`` is a preallocated array of
mjContact data structures, populated at runtime with the contacts found by the collision detector. Additional contact
information is then filled-in by the simulator.

.. mujoco-include:: mjContact


.. _mjResource:

mjResource

This is the data structure of the virtual file system. It can only be constructed programmatically, and does not
have an analog in MJCF.

.. mujoco-include:: mjVFS


.. _mjLROpt:

mjLROpt

Asset cache used by the compiler to avoid repeated slow recompilation. See :ref:`Asset cache<Assetcache>`.

.. mujoco-include:: mjCache

.. _mjtTaskStatus:

mjtTaskStatus

This is a representation of a task to be run asynchronously inside of an :ref:`mjThreadPool` . It is created in the
:ref:`mju_threadPoolEnqueue` method of the :ref:`mjThreadPool`  and is used to join the task at completion.
The ``status`` field uses values from :ref:`mjtTaskStatus`.

.. mujoco-include:: mjTask

.. _mjThreadPool:

mjThreadPool

This is the data structure holding information about one warning type. ``mjData.warning`` is a preallocated array of
mjWarningStat data structures, one for each warning type.

.. mujoco-include:: mjWarningStat


.. _mjTimerStat:

mjTimerStat
~~~~~~~~~~~

This is the data structure holding information about one timer. ``mjData.timer`` is a preallocated array of
mjTimerStat data structures, one for each timer type.

.. mujoco-include:: mjTimerStat


.. _mjSolverStat:

mjSolverStat
~~~~~~~~~~~~

This is the data structure holding information about one solver iteration. ``mjData.solver`` is a preallocated array
of mjSolverStat data structures, one for each iteration of the solver, up to a maximum of mjNSOLVER. The actual number
of solver iterations is given by ``mjData.solver_niter``.

.. mujoco-include:: mjSolverStat



.. _tyVisStructure:

Visualisation
^^^^^^^^^^^^^

The names of these struct types are prefixed with ``mjv``.

.. _mjvPerturb:

mjvPerturb
~~~~~~~~~~

This is the data structure holding information about mouse perturbations.

.. mujoco-include:: mjvPerturb


.. _mjvCamera:

mjvCamera
~~~~~~~~~

This is the data structure describing one abstract camera.

.. mujoco-include:: mjvCamera


.. _mjvGLCamera:

mjvGLCamera
~~~~~~~~~~~

This is the data structure describing one OpenGL camera.

.. mujoco-include:: mjvGLCamera


.. _mjvGeom:

mjvGeom
~~~~~~~

This is the data structure describing one abstract visualization geom - which could correspond to a model geom or to a
decoration element constructed by the visualizer.

.. mujoco-include:: mjvGeom


.. _mjvLight:

mjvLight
~~~~~~~~

This is the data structure describing one OpenGL light.

.. mujoco-include:: mjvLight


.. _mjvOption:

mjvOption
~~~~~~~~~

This structure contains options that enable and disable the visualization of various elements.

.. mujoco-include:: mjvOption


.. _mjvScene:

mjvScene
~~~~~~~~

This structure contains everything needed to render the 3D scene in OpenGL.

.. mujoco-include:: mjvScene


.. _mjvFigure:

mjvFigure
~~~~~~~~~

This structure contains everything needed to render a 2D plot in OpenGL. The buffers for line points etc. are
preallocated, and the user has to populate them before calling the function :ref:`mjr_figure` with this
data structure as an argument.

.. mujoco-include:: mjvFigure


.. _tyRenderStructure:

Rendering
^^^^^^^^^

The names of these struct types are prefixed with ``mjr``.

.. _mjrRect:

mjrRect
~~~~~~~

This structure specifies a rectangle.

.. mujoco-include:: mjrRect


.. _mjrContext:

mjrContext
~~~~~~~~~~

This structure contains the custom OpenGL rendering context, with the ids of all OpenGL resources uploaded to the GPU.

.. mujoco-include:: mjrContext


.. _tyUIStructure:

User Interface
^^^^^^^^^^^^^^

For a high-level description of the UI framework, see :ref:`UI`.
The names of these struct types are prefixed with ``mjui``, except for the main :ref:`mjUI` struct itself.


.. _mjuiState:

mjuiState
~~~~~~~~~

This C struct represents the global state of the window, keyboard and mouse, input event descriptors, and all window
rectangles (including the visible UI rectangles). There is only one ``mjuiState`` per application, even if there are
multiple UIs. This struct would normally be defined as a global variable.

.. mujoco-include:: mjuiState


.. _mjuiThemeSpacing:

mjuiThemeSpacing

This structure defines the colors of UI items in the theme.

.. mujoco-include:: mjuiThemeColor


.. _mjuiItem:

mjuiItem
~~~~~~~~

This structure defines one UI item.

.. mujoco-include:: mjuiItem


.. _mjuiSection:

mjuiSection
~~~~~~~~~~~

This structure defines one section of the UI.

.. mujoco-include:: mjuiSection


.. _mjuiDef:

mjuiDef
~~~~~~~

This structure defines one entry in the definition table used for simplified UI construction. It contains everything
needed to define one UI item. Some translation is performed by the helper functions, so that multiple mjuiDefs can be
defined as a static table.

.. mujoco-include:: mjuiDef


.. _mjUI:

mjUI
~~~~

This C struct represents an entire UI. The same application could have multiple UIs, for example on the left and the
right of the window. This would normally be defined as a global variable. As explained earlier, it contains static
allocation for a maximum number of supported UI sections (:ref:`mjuiSection<mjuiSection>`) each with a maximum number
of supported items (:ref:`mjuiItem<mjuiItem>`). It also contains the color and spacing themes, enable/disable
callback, virtual window descriptor, text edit state, mouse focus. Some of these fields are set only once when the UI
is initialized, others change at runtime.

.. mujoco-include:: mjUI



.. _tySpecStructure:

Model Editing
^^^^^^^^^^^^^

The structs below are defined in
`mjspec.h <https://github.com/google-deepmind/mujoco/blob/main/include/mujoco/mjspec.h>`__ and, with the exception of
the top level :ref:`mjSpec` struct, begin with the ``mjs`` prefix. For more details, see the :doc:`Model Editing
<../programming/modeledit>` chapter.

.. _mjSpec:

mjSpec
~~~~~~

Model specification.

.. mujoco-include:: mjSpec


.. _mjsElement:

mjsElement
~~~~~~~~~~

Special type corresponding to any element. This struct is the first member of all other elements; in the low-level C++
implementation, it is not included as a member but via class inheritance. Inclusion via inheritance allows the compiler
to ``static_cast`` an ``mjsElement`` to the correct C++ object class. Unlike all other attributes of the structs below,
which are user-settable by design, modifying the contents of an ``mjsElement`` is not allowed and leads to undefined
behavior.

.. mujoco-include:: mjsElement


.. _mjsCompiler:

mjsCompiler
~~~~~~~~~~~

Compiler options.

.. mujoco-include:: mjsCompiler


.. _mjsBody:

mjsBody
~~~~~~~

Body specification.

.. mujoco-include:: mjsBody


.. _mjsFrame:

mjsFrame
~~~~~~~~

Frame specification.

.. mujoco-include:: mjsFrame


.. _mjsJoint:

mjsJoint
~~~~~~~~

Joint specification.

.. mujoco-include:: mjsJoint


.. _mjsGeom:

mjsGeom
~~~~~~~

Geom specification.

.. mujoco-include:: mjsGeom


.. _mjsSite:

mjsSite
~~~~~~~

Site specification.

.. mujoco-include:: mjsSite


.. _mjsCamera:

mjsCamera
~~~~~~~~~

Camera specification.

.. mujoco-include:: mjsCamera


.. _mjsLight:

mjsLight
~~~~~~~~

Light specification.

.. mujoco-include:: mjsLight


.. _mjsFlex:

mjsFlex
~~~~~~~

Flex specification.

.. mujoco-include:: mjsFlex


.. _mjsMesh:

mjsMesh
~~~~~~~

Mesh specification.

.. mujoco-include:: mjsMesh


.. _mjsHField:

mjsHField
~~~~~~~~~

Height field specification.

.. mujoco-include:: mjsHField


.. _mjsSkin:

mjsSkin
~~~~~~~

Skin specification.

.. mujoco-include:: mjsSkin


.. _mjsTexture:

mjsTexture
~~~~~~~~~~

Texture specification.

.. mujoco-include:: mjsTexture


.. _mjsMaterial:

mjsMaterial
~~~~~~~~~~~

Material specification.

.. mujoco-include:: mjsMaterial


.. _mjsPair:

mjsPair
~~~~~~~

Pair specification.

.. mujoco-include:: mjsPair


.. _mjsExclude:

mjsExclude
~~~~~~~~~~

Exclude specification.

.. mujoco-include:: mjsExclude


.. _mjsEquality:

mjsEquality
~~~~~~~~~~~

Equality specification.

.. mujoco-include:: mjsEquality


.. _mjsTendon:

mjsTendon
~~~~~~~~~

Tendon specification.

.. mujoco-include:: mjsTendon


.. _mjsWrap:

mjsWrap
~~~~~~~

Wrapping object specification.

.. mujoco-include:: mjsWrap


.. _mjsActuator:

mjsActuator
~~~~~~~~~~~

Actuator specification.

.. mujoco-include:: mjsActuator


.. _mjsSensor:

mjsSensor
~~~~~~~~~

Sensor specification.

.. mujoco-include:: mjsSensor


.. _mjsNumeric:

mjsNumeric
~~~~~~~~~~

Custom numeric field specification.

.. mujoco-include:: mjsNumeric


.. _mjsText:

mjsText
~~~~~~~

Custom text specification.

.. mujoco-include:: mjsText


.. _mjsTuple:

mjsTuple
~~~~~~~~

Tuple specification.

.. mujoco-include:: mjsTuple


.. _mjsKey:

mjsKey
~~~~~~

Keyframe specification.

.. mujoco-include:: mjsKey


.. _mjsDefault:

mjsDefault
~~~~~~~~~~

Default specification.

.. mujoco-include:: mjsDefault


.. _mjsPlugin:

mjsPlugin
~~~~~~~~~

Plugin specification.

.. mujoco-include:: mjsPlugin


.. _mjsOrientation:

mjsOrientation

C handles for C++ strings and vector types. When using from C, use the provided :ref:`getters<AttributeGetters>` and
:ref:`setters<AttributeSetters>`.

.. code-block:: C++

   #ifdef __cplusplus
     // C++: defined to be compatible with corresponding std types
     using mjString      = std::string;
     using mjStringVec   = std::vector<std::string>;
     using mjIntVec      = std::vector<int>;
     using mjIntVecVec   = std::vector<std::vector<int>>;
     using mjFloatVec    = std::vector<float>;
     using mjFloatVecVec = std::vector<std::vector<float>>;
     using mjDoubleVec   = std::vector<double>;
     using mjByteVec     = std::vector<std::byte>;
   #else
     // C: opaque types
     typedef void mjString;
     typedef void mjStringVec;
     typedef void mjIntVec;
     typedef void mjIntVecVec;
     typedef void mjFloatVec;
     typedef void mjFloatVecVec;
     typedef void mjDoubleVec;
     typedef void mjByteVec;
   #endif


.. _tyPluginStructure:

Plugins
^^^^^^^

The names of these struct types are prefixed with ``mjp``. See :ref:`exPlugin` for more details.


.. _mjpPlugin:

mjpPlugin
~~~~~~~~~

This structure contains the definition of a single engine plugin. It mostly contains a set of callbacks, which are
triggered by the compiler and the engine during various phases of the computation pipeline.

.. mujoco-include:: mjpPlugin

.. _mjSDF:

mjSDF
~~~~~

Data structure used by the :ref:`Signed Distance Functions<Signeddistancefunction>` API for computing distances and
gradients between SDF geoms.

.. mujoco-include:: mjSDF

.. _mjpResourceProvider:

mjpResourceProvider

This data structure defines a decoder. It contains a set of callbacks used for decoding :ref:`mjResource`
into :ref:`mjSpec`.

.. mujoco-include:: mjpDecoder

.. _mjpEncoder:

mjpEncoder

.. code-block:: C

   typedef void (*mjfGeneric)(const mjModel* m, mjData* d);

This is the function type of the callbacks :ref:`mjcb_passive` and :ref:`mjcb_control`.


.. _mjfConFilt:

mjfConFilt

.. code-block:: C

   typedef void (*mjfSensor)(const mjModel* m, mjData* d, int stage);

This is the function type of the callback :ref:`mjcb_sensor`.


.. _mjfTime:

mjfTime
~~~~~~~

.. code-block:: C

   typedef mjtNum (*mjfTime)(void);

This is the function type of the callback :ref:`mjcb_time`.


.. _mjfAct:

mjfAct
~~~~~~

.. code-block:: C

   typedef mjtNum (*mjfAct)(const mjModel* m, const mjData* d, int id);

This is the function type of the callbacks :ref:`mjcb_act_dyn`, :ref:`mjcb_act_gain` and :ref:`mjcb_act_bias`.


.. _mjfCollision:

mjfCollision

.. code-block:: C

   typedef int (*mjfItemEnable)(int category, void* data);

This is the function type of the predicate function used by the UI framework to determine if each item is enabled or
disabled.

.. _tyRPCallbacks:

Resource Provider Callbacks
^^^^^^^^^^^^^^^^^^^^^^^^^^^

These callbacks are used by :ref:`resource providers<exProvider>`.

.. _mjfOpenResource:

mjfOpenResource

.. code-block:: C

   typedef int (*mjfReadResource)(mjResource* resource, const void** buffer);

This callback is for reading a resource. Returns number of bytes stored in buffer and returns -1 on error.

.. _mjfCloseResource:

mjfCloseResource

.. code-block:: C

   typedef void (*mjfGetResourceDir)(mjResource* resource, const char** dir, int* ndir);

This callback is for returning the directory of a resource, by setting dir to the directory string with ndir being size
of directory string.

.. _mjfResourceModified:

mjfResourceModified

.. code-block:: C

   typedef mjSpec* (*mjfDecode)(mjResource* resource, const mjVFS* vfs);


This callback is given an opened resource, and is responsible for decoding it into a :ref:`mjSpec`.
Ownership of the resource and the returned spec is responsibility of the caller.
When decoding fails, the callback should return NULL.

.. _mjfCanDecode:

mjfCanDecode

.. code-block:: C

   typedef int (*mjfEncode)(const mjSpec* s, const mjModel* m, const mjVFS* vfs,
                            mjResource* resource);


This callback populates the :ref:`mjResource<mjResource>` `data` member with bytes representing the
given spec in the format associated with the owning plugin. This may be called with the associated
compiled :ref:`mjModel`.


.. _tyNotes:

Notes
-----

This section contains miscellaneous notes regarding data-structure conventions in MuJoCo struct types.


.. _tyNotesCom:

c-frame variables
^^^^^^^^^^^^^^^^^

:ref:`mjData` contains two arrays with the ``c`` prefix, which are used for internal calculations: ``cdof`` and
``cinert``, both computed by :ref:`mj_comPos`. The ``c`` prefix means that quantities are with respect to the "c-frame",
a frame at the center-of-mass of the local kinematic subtree (``mjData.subtree_com``), oriented like the world frame.
This choice increases the precision of kinematic computations for mechanisms that are distant from the global origin.

``cdof``:
  These 6D motion vectors (3 rotation, 3 translation) describe the instantaneous axis of a degree-of-freedom and are
  used by all Jacobian functions. The minimal computation required for analytic Jacobians is :ref:`mj_kinematics`
  followed by :ref:`mj_comPos`.

``cinert``:
  These 10-vectors describe the inertial properties of a body in the c-frame and are used by the Composite Rigid Body
  algorithm (:ref:`mj_crb`). The 10 numbers are packed arrays of lengths (6, 3, 1) with semantics:

  ``cinert[0-5]``: Upper triangle of the body's inertia matrix.

  ``cinert[6-8]``: Body mass multiplied by the body CoM's offset from the c-frame origin.

  ``cinert[9]``: Body mass.

.. _tyNotesConvex:

Convex hulls
^^^^^^^^^^^^

The convex hull descriptors are stored in :ref:`mjModel`:

.. code-block:: C

   int*      mesh_graphadr;     // graph data address; -1: no graph      (nmesh x 1)
   int*      mesh_graph;        // convex graph data                     (nmeshgraph x 1)

If mesh ``N`` has a convex hull stored in :ref:`mjModel` (which is optional), then ``m->mesh_graphadr[N]`` is the offset
of mesh ``N``'s convex hull data in ``m->mesh_graph``. The convex hull data for each mesh is a record with the following
format:

.. code-block:: C

   int numvert;
   int numface;
   int vert_edgeadr[numvert];
   int vert_globalid[numvert];
   int edge_localid[numvert+3*numface];
   int face_globalid[3*numface];

Note that the convex hull contains a subset of the vertices of the full mesh. We use the nomenclature ``globalid`` to
refer to vertex indices in the full mesh, and ``localid`` to refer to vertex indices in the convex hull. The meaning of
the fields is as follows:

``numvert``
   Number of vertices in the convex hull.

``numface``
   Number of faces in the convex hull.

``vert_edgeadr[numvert]``
   For each vertex in the convex hull, this is the offset of the edge record for that vertex in edge_localid.

``vert_globalid[numvert]``
   For each vertex in the convex hull, this is the corresponding vertex index in the full mesh

``edge_localid[numvert+3*numface]``
   This contains a sequence of edge records, one for each vertex in the convex hull. Each edge record is an array of
   vertex indices (in localid format) terminated with -1. For example, say the record for vertex 7 is: 3, 4, 5, 9, -1.
   This means that vertex 7 belongs to 4 edges, and the other ends of these edges are vertices 3, 4, 5, 9. In this way
   every edge is represented twice, in the edge records of its two vertices. Note that for a closed triangular mesh
   (such as the convex hulls used here), the number of edges is ``3*numface/2``. Thus when each edge is represented
   twice, we have ``3*numface edges``. And since we are using the separator -1 at the end of each edge record (one
   separator per vertex), the length of ``edge_localid`` is ``numvert+3*numface``.

``face_globalid[3*numface]``
   For each face of the convex hull, this contains the indices of the three vertices in the full mesh