Use mesh BVH for speeding up ray mesh intersection.

PiperOrigin-RevId: 534141245
Change-Id: I9f5a71ea059a1a232fd2910d1efc0506ab6dbef3

doc/APIreference/APIglobals.rst

@@ -409,6 +409,10 @@ table below. Their names are in the format ``mjKEY_XXX``. They correspond to GLF
        respect this limit, and user-defined functions should also respect it. Such functions are called with a return
        buffer of size ``mjMAXCONPAIR``; attempting to write more contacts in the buffer can cause unpredictable
        behavior.
+   * - ``mjMAXTREEDEPTH``
+     - 50
+     - The maximum depth of each body and mesh bounding volume hierarchy. If this large limit is exceeded, a warning
+       is raised and ray casting may not be possible. For a balanced hierarchy, this implies 1E15 bounding volumes.
    * - ``mjMAXVFS``
      - 200
      - The maximal number of characters in the name of each file in the virtual file system.

doc/changelog.rst

@@ -32,6 +32,7 @@ General
   trajectory optimization. See :ref:`mju_cholFactorBand` documentation for details.
 - Added :ref:`mj_multiRay` function for intersecting multiple rays emanating from a single point.
   This is significantly faster than calling :ref:`mj_ray` multiple times.
+- Ray-mesh collisions are now up to 10x faster, using a bounding volume hierarchy of mesh faces.
 - Increased ``mjMAXUIITEM`` (maximum number of UI elements per section in Simulate) to 100.
 - Added :ref:`documentation<exProvider>` for resource providers.
 - Changed the formula for :ref:`mju_sigmoid`, a finite-support sigmoid :math:`s \colon \mathbf R \rightarrow [0, 1]`.