warp.mesh\_get\_index
=====================

.. function:: warp._src.lang.mesh_get_index(id: uint64, index: int32) -> int

   .. hlist::
      :columns: 8

      * Kernel

   Look up the vertex index stored at a face-vertex position in the :class:`warp.Mesh`'s index buffer.
   
   ``index`` is a *face-vertex index* in ``[0, 3 * number_of_faces)``; returns the vertex index it
   stores (``indices[index]``), which in turn indexes the mesh's points array.
   
   :param id: The mesh identifier
   :param index: A face-vertex index, in ``[0, 3 * number_of_faces)``
   
   :returns: The vertex index stored at that position, or -1 if the mesh has no index buffer.
   
   .. rubric:: Example
   
   .. testcode::
   
       @wp.kernel
       def face0_verts(mesh_id: wp.uint64, out: wp.array[wp.int32]):
           out[0] = wp.mesh_get_index(mesh_id, 0)
           out[1] = wp.mesh_get_index(mesh_id, 1)
           out[2] = wp.mesh_get_index(mesh_id, 2)
   
       points = wp.array([[0,0,0],[1,0,0],[1,1,0],[0,1,0],[0,0,1],[1,0,1],[1,1,1],[0,1,1]], dtype=wp.vec3)
       indices = wp.array([0,3,2, 0,2,1,  4,5,6, 4,6,7,  0,1,5, 0,5,4,
                           2,3,7, 2,7,6,  0,4,7, 0,7,3,  1,2,6, 1,6,5], dtype=wp.int32)
       mesh = wp.Mesh(points=points, indices=indices)
   
       out = wp.zeros(3, dtype=wp.int32)
       wp.launch(face0_verts, dim=1, inputs=[mesh.id], outputs=[out])
       print(out.numpy())
   
   .. testoutput::
   
       [0 3 2]