Supported File Formats

The ovf format is the suggested file format for mmDisp when the grid is uniform. It will allow for the fastest loading of data and will give the best performance with a uniform grid.
The svf format will load slower but is simpler to program and supports non-uniformly-sampled data.

OVF Format Overview

The OOMMF vector field file format, ovf, is the native file format for mmDisp. It currently supports ASCII or binary data stored on rectangular grids. An example file is available as well as a commented header file.

Basic Syntax: The ovf format consists of three parts: the header, the data block and the footer.
The header assures mmdisp that it is really reading a ovf file and gives information about the dimensions of the vector plot. Each new line of the header is started with the control character, '#'.
- Control lines have a '#' character in front. Comments are designated by two '#' characters. Note that a new line is only designated by the '#' character. Spaces, tabs, and returns while available and encouraged for clarity are ignored.
  Examples:
```
##I am a comment line.  Notice my two number characters.
#OOMMF: rectangular mesh v0.0a0  ##The left is a control line.
```
The data block holds the data in either binary or ASCII format.
The footer denotes the end of the file.

The contents of each segment-

The Header:
- File description tag: This tag tells mmDisp that the file is an ovf file and also the type of mesh that the data is stored on. Currently the ovf format only supports data on a rectangular grid so the line must be:
  Example:
```
# OOMMF: rectangular mesh v0.0a0
```
- Segment count: tells mmDisp the number of segments, or display frames, in the file. For the current version of mmDisp only one segment is allowed and the line should be:
  Example:
```
# segment count: 1
```
- Begin statements: Two begin statements are needed. The first directs mmDisp to start a new segment, the other tells mmDisp to start the header for the segment.
  Example:
```
# Begin: Segment
# Begin: Header
```
- Title statement: A line giving the title of the .ovf file is required.
  Example:
```
#Title: Micromagnetic simulation results for 29 February 1973.
```
- Meshunits: A line that gives units for the grid spacing is needed. The line is treated as a label; MmDisp does not currently use this data but it is possible that later releases will. Currently mmDisp will except anything after meshunit.
  Example:
```
#meshunit: NM
```
- {XYZ}Base: Three data points that specify the origin of the mesh bounding box is needed. The mesh bounding box is a rectangle that mmDisp draws around the data. The origin is taken to be the lower left corner of mmDisp's display.
  Example:
```
# xbase: 0.
# ybase: 0.
# zbase: 0.
```
- {XYZ}Stepsize: This data field specifies the distance between adjacent grid points in units given in the command meshunit. The stepsize is used by mmDisp to draw the bounding box. A negative value for step size will reverse the order that the data is displayed. If a negative value is used for step size, the min&max value described below will have to be made negative also.
  Example:
```
#xstepsize:20.
#ystepsize:20.
#zstepsize:10.
```
- {XYZ}Nodes: Nodes gives the number of data points in the x,y and z directions. The number of nodes must be an integer. Note also that currently the only valid value for znodes is one.
  Example:
```
#xnodes: 2000
#ynodes: 4000
#znodes: 1
```
- min&max: The min and max commands are used by mmDisp to draw the bounding rectangle about the data. The commands define the minimum and maximum value of of the corners of the bounding rectangle. For most applications the min values should be slightly less than than zero and the max values should be the number of nodes times the stepsize. This will result in a rectangle that is just slightly greater in size than the data region.
  Example:
```
# xmin: -.5
# ymin: -.5
# zmin: -.5
# xmax: 20000
# ymax: 20000
# zmax: .5
```
- ValueUnit: This command is used to record the unit for field. Currently is not used by mmDisp, but must be included.
  Example:
```
# valueunit: kA/m
```
- Valuemultiplier: This value is a factor that is multiplied by the field values to get a true value in valueunits.
  Example:
```
# valuemultiplier: 1.0
```
- ValueRange{Max Min}Mag: This entry determines the maximum and minimum value of the vectors that the program will display. MmDisp will not display any points with a value less than ValueRangeMinMag and will use ValueRangeMaxMag to scale the vectors that the program displays.
  Example:
```
# ValueRangeMaxMag: 1.0
# ValueRangeMinMag: 1.0E-8
```
- End header: This command must be located at the end of the header and the command defines the end of the ovf file's header.
  Example:
```
# End: Header
```
The Data Block:
- The ovf format currently allows data saved in both ASCII and network-byte-order (MSB) IEEE floating point binary data blocks. For both methods of saving data the data should be saved to the file in Fortran order, that is the x-axis is incremented first then the y-axis and finally the z-axis.
  - Text Data Storage: Text data is saved in the order of x-component, y-component, z-component. Each entry must be separated by whitespace, any amount in kind is allowed e.g. space, tab. The beginning of a text block is indicated by the command:
```
#Begin: data text
```
    Likewise the end of the text data block must have the command:
```
#End: data text
```
  - Binary Data Storage: Binary data in order of x-component, y-component, z-component. Each component is assumed to be made up of a 4 or 8 byte block. The data must be saved with the most significant byte, MSB, first.
    - Binary data blocks begin with the command:
      #Begin: data binary 4
      or
      #Begin: data binary 8
    - The first number in the binary data field must be a check value to insure that the data is saved in MSB order and to reassure the reading program that it is reading four or eight byte blocks. The check value for 4 byte data blocks is 1234567. The check value for 8 byte data blocks is 123456789012345. Again, the start of each binary data block must have this value.
    - The end of a binary data block must include the line:
      #End: data binary 4
      or
      #End: data binary 8
      as appropriate.
The Footer: Every omf file ends with the line
```
#End: segment
```
which tells mmDisp the end of the file has been reached.

SVF Format Overview

The svf format has two parts- a header section and a data section.

The Header:
- The first line of the header file for the svf format reassures the program that is reading an svf file. The line must be:
```
#SVF-02
```
- The above line is the only required header line for the svf format. Comment lines can also be included in the header and will start with one '#' character.
```
#File: mag6000.svf
```
- Three optional header commands are supported. The first command defines an in-plane polygon that bounds the data. It is given in x,y pairs with a line being drawn between the each pair of point pairs. The polygon does not have to be closed and no limit is put on the number of points in the polygon. The units are the same as the ones used in the data area described below. An example of the command for creating a bounding polygon is:
```
## Boundary-XY:0.0 0.0 1.0 0.0 1.0 2.0 0.0 2.0 0.0 0.0
```
- The second useful but not required header command is the command that defines the step size of a uniform grid mask used to calculate the number of displayed data points at a particular subsample rate. If not given, the program will calculate the value by calculating the area of the smallest rectangle that will display all the data and dividing by the number of data points. However, this calculation can be far off for data that does not located in a rectangular region and for grids where the data points are clumped together. MmDisp will still run in this situation but the subsample rate will likely have to be adjusted to produce a good plot of the data. To avoid this difficulty simply give the program a good estimate of the grid step with the command grid step {x y z}:
```
## Grid Step: .02 .02 0.0
```
- The final optional header command is used to give the name of the file. This can be different from the name the file is stored under. The command to specify the filename is:
```
## File: filename
```
The Data Section:
- For each vector in the file six numbers, saved as ASCII data, are needed. The first three specify the location of the vector and is saved in the order {x,y,z} the second is the magnitude of each component of the vector and is also saved in order {x,y,z}. An example is shown below.
```
0.01   0.01   0.01   -0.35537  0.93472 -0.00000
```
  The vectors can be written to the file in any order.

Go to the top