warp.volume\_lookup
===================

.. function:: warp._src.lang.volume_lookup(id: uint64, i: int32, j: int32, k: int32, dtype: Any) -> Any

   .. hlist::
      :columns: 8

      * Kernel

   Return the value of type ``dtype`` stored at the voxel with integer index-space coordinates
   ``i``, ``j``, ``k``, without interpolation.
   
   ``dtype`` must match the volume's stored value type. This function is not differentiable; use
   :func:`~warp.volume_sample` for interpolated reads of floating-point scalar and vector data.
   
   :param id: The ``id`` of a :class:`warp.Volume`.
   :param i: Voxel coordinate along the first index-space axis (may be negative).
   :param j: Voxel coordinate along the second index-space axis (may be negative).
   :param k: Voxel coordinate along the third index-space axis (may be negative).
   :param dtype: Value type stored by the volume (see :func:`~warp.volume_sample`).
   
   :returns: the stored value, or the volume's background
             value when the location has no stored value.
   :rtype: The resolved voxel value of type ``dtype``
   
   .. rubric:: Example
   
   .. testcode::
   
       @wp.kernel
       def lookup(vid: wp.uint64, out: wp.array[wp.float32]):
           out[0] = wp.volume_lookup(vid, 1, 0, 0, dtype=float)
   
       values = np.zeros((2, 2, 2), dtype=np.float32)
       values[1, :, :] = 1.0  # f(i, j, k) = i
       volume = wp.Volume.load_from_numpy(values, voxel_size=1.0, bg_value=0.0)
       out = wp.zeros(1, dtype=wp.float32)
       wp.launch(lookup, dim=1, inputs=[volume.id], outputs=[out])
       print(round(float(out.numpy()[0]), 1))
   
   .. testoutput::
   
       1.0