Expose mju_sparse2dense to public API.

PiperOrigin-RevId: 688985153
Change-Id: I9559f1d47363d0afada80c86abdc729cd1910b63

doc/APIreference/APIfunctions.rst

@@ -38,6 +38,7 @@ API function can be classified as:
 - **Math**
    - Aliases for C :ref:`standard math<Standardmath>` functions.
    - :ref:`Vector math<Vectormath>`.
+   - :ref:`Sparse math<Sparsemath>`.
    - :ref:`Quaternions<Quaternions>`.
    - :ref:`Pose transformations<Poses>`.
    - :ref:`Matrix decompositions and solvers<Decompositions>`.

doc/APIreference/functions.rst

@@ -3440,6 +3440,19 @@ mju_transformSpatial
 Coordinate transform of 6D motion or force vector in rotation:translation format.
 rotnew2old is 3-by-3, NULL means no rotation; flg_force specifies force or motion type.
 
+.. _Sparsemath:
+
+Sparse math
+^^^^^^^^^^^
+.. _mju_sparse2dense:
+
+mju_sparse2dense
+~~~~~~~~~~~~~~~~
+
+.. mujoco-include:: mju_sparse2dense
+
+Convert matrix from sparse to dense.
+
 .. _Quaternions:
 
 Quaternions

doc/includes/references.h

@@ -3467,6 +3467,8 @@ void mju_sqrMatTD(mjtNum* res, const mjtNum* mat, const mjtNum* diag, int nr, in
 void mju_transformSpatial(mjtNum res[6], const mjtNum vec[6], int flg_force,
                           const mjtNum newpos[3], const mjtNum oldpos[3],
                           const mjtNum rotnew2old[9]);
+void mju_sparse2dense(mjtNum* res, const mjtNum* mat, int nr, int nc,
+                      const int* rownnz, const int* rowadr, const int* colind);
 void mju_rotVecQuat(mjtNum res[3], const mjtNum vec[3], const mjtNum quat[4]);
 void mju_negQuat(mjtNum res[4], const mjtNum quat[4]);
 void mju_mulQuat(mjtNum res[4], const mjtNum quat1[4], const mjtNum quat2[4]);