The OVF 0.0 format

The OVF 0.0 format is a simple ASCII text format supporting irregularly sampled data. It is intended as an aid for importing data from non-OOMMF programs, and is backwards compatible with the format used for problem submissions for the first muMAG standard problem.

Users of early releases of OOMMF may recognize the OVF 0.0 format by its previous name, the Simple Vector Field (SVF) format. It came to the attention of the OOMMF developers that the file extension .svf was already registered in several MIME systems to indicate the Simple Vector Format, a vector graphics format. To avoid conflict, we have stopped using the name Simple Vector Field format, although OOMMF software still recognizes the .svf extension and you may still find example files and other references to the SVF format.

A sample OVF 0.0 file is shown below. Any line beginning with a `#' character is a comment, all others are data lines. Each data line is a whitespace separated list of 6 elements: the $x$, $y$ and $z$ components of a node position, followed by the $x$, $y$ and $z$ components of the field at that position. Input continues until the end of the file is reached.

It is recommended (but not required) that the first line of an OVF file be

# OOMMF: irregular mesh v0.0

This will aid automatic file type detection. Also, three special (extended) comments in OVF 0.0 files are recognized by mmDisp:

## File: <filename or extended filename>
## Boundary-XY: <boundary vertex pairs>
## Grid step: <cell dimension triple>

All these lines are optional. The “File” provides a preferred (possibly extended) filename to use for display identification. The “Boundary-XY” line specifies the ordered vertices of a bounding polygon in the $xy$-plane. If given, mmDisp will draw a frame using those points to ostensibly indicate the edges of the simulation body. Lastly, the “Grid step” line provides three values representing the average $x$, $y$ and $z$ dimensions of the volume corresponding to an individual node (field sample). It is used by mmDisp to help scale the display.

Note that the data section of an OVF 0.0 file takes the simple form of columns of ASCII formatted numbers. Columns of whitespace separated numbers expressed in ASCII are easy to import into other programs that process numerical datasets, and are easy to generate, so the OVF 0.0 file format is useful for exchanging vector field data between OOMMF and non-OOMMF programs. Furthermore, the data section of an OVF 0.0 file is consistent with the data section of an OVF 1.0 file that has been saved as an irregular mesh using text data representation. This means that even though OOMMF software now writes only the OVF 1.0 format for vector field data, simple interchange of vector field data with other programs is still supported.

# OOMMF: irregular mesh v0.0
## File: sample.ovf
## Boundary-XY: 0.0 0.0 1.0 0.0 1.0 2.0 0.0 2.0 0.0 0.0
## Grid step: .25 .5 0
#  x      y      z        m_x      m_y      m_z
  0.01   0.01   0.01   -0.35537  0.93472 -0.00000
  0.01   1.00   0.01   -0.18936  0.98191 -0.00000
  0.01   1.99   0.01   -0.08112  0.99670 -0.00000
  0.50   0.50   0.01   -0.03302  0.99945 -0.00001
  0.99   0.05   0.01   -0.08141  0.99668 -0.00001
  0.75   1.50   0.01   -0.18981  0.98182 -0.00000
  0.99   1.99   0.01   -0.35652  0.93429 -0.00000

Figure 19.1: Example OVF 0.0 file. (description)

OOMMF Documentation Team
September 27, 2024