.. _dirrotate:

dirrotate
===================

Synopsis
--------

Apply a rotation to a direction set

Usage
--------

::

    dirrotate [ options ]  in out

-  *in*: the input direction file
-  *out*: the output direction file

Description
-----------

The primary use case of this command is to find, for a given basis direction set, an appropriate rotation that preserves the homogeneity of coverage on the sphere but that minimises the maximal peak amplitude along the physical axes of the scanner, so as to minimise the peak gradient system demands. It can alternatively be used to introduce a random rotation to hopefully prevent any collinearity between directions in different shells, by requesting only a single rotation.

Options
-------

-  **-number num** number of rotations to try (default: 10000000)

-  **-cartesian** Output directions in Cartesian coordinates [x y z] instead of spherical angles [az in].

Standard options
^^^^^^^^^^^^^^^^

-  **-info** display information messages.

-  **-quiet** do not display information messages or progress status; alternatively, this can be achieved by setting the MRTRIX_QUIET environment variable to a non-empty string.

-  **-debug** display debugging messages & debug input data.

-  **-force** force overwrite of output files (caution: using the same file as input and output might cause unexpected behaviour).

-  **-nthreads number** use this number of threads in multi-threaded applications (set to 0 to disable multi-threading).

-  **-config key value** *(multiple uses permitted)* temporarily set the value of an MRtrix config file entry.

-  **-help** display this information page and exit.

-  **-version** display version information and exit.

References
^^^^^^^^^^

Tournier, J.-D.; Smith, R. E.; Raffelt, D.; Tabbara, R.; Dhollander, T.; Pietsch, M.; Christiaens, D.; Jeurissen, B.; Yeh, C.-H. & Connelly, A. MRtrix3: A fast, flexible and open software framework for medical image processing and visualisation. NeuroImage, 2019, 202, 116137

--------------



**Author:** Robert E. Smith (robert.smith@florey.edu.au)

**Copyright:** Copyright (c) 2008-2026 the MRtrix3 contributors.

This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.

Covered Software is provided under this License on an "as is"
basis, without warranty of any kind, either expressed, implied, or
statutory, including, without limitation, warranties that the
Covered Software is free of defects, merchantable, fit for a
particular purpose or non-infringing.
See the Mozilla Public License v. 2.0 for more details.

For more details, see http://www.mrtrix.org/.