Mum: Modelling using moiré

The primary input file for Mum is a .mum file which contains:

• x and y spacing parameters (cm/pixel) and a z spacing parameter (cm/radian or cm/fringe).
• a list of moiré images (.img files, or .xyz files which will automatically be converted to Mum's .img format).
• line and point definitions in a format similar to, but less general than, Fud's format for lines and points. A line definition includes a line name, a set of boundary conditions, and optional qualifiers to control mesh generation and line joins. A point definition is just an (x,y,z) triplet.
• surface definitions and finite-element parameters in the same format that Fud uses. (Mum just blindly writes them into .fud files.)

Mum provides facilities for

• exploring the moiré data by displaying profiles
• doing manual and semi-automatic phase unwrapping of the moiré data
• defining and revising model outlines (sets of line and point definitions). These outlines are used by Fud for finite-element mesh generation. Line definitions can be typed directly into the .mum file, or can be imported from another .mum file. The corresponding point definitions can also be typed directly into the .mum file or imported from another .mum file , or they can be imported from a pre-existing .fud file (often from a previously created model) or from image-analyzer files.
• applying z coordinates to 2-D finite-element meshes. Mum imports .sap files, uses the moiré data to define z coordinates for nodes which don't yet have z coordinates, and writes out a new .sap file.

The usual processing sequence is the following:

1. Create (or adapt) a .mum file.
2. Do any required phase unwrapping.
3. Define (or adapt) outlines with x,y,z coordinates.
4. Write out a .fud file.
5. Use Fud to generate a finite-element mesh.
6. Use Mum to apply z coordinates to the newly generated internal nodes in the finite-element mesh:
   1. FileRead .mum
   2. Specify .mum file from which the model was generated.
   3. FileModify .sap
      
   4. Specify .fud file from which the model was generated. This .fud file may have been generated directly by Mum or may have been manually modified. It does not need to be in the same directory as the .mum file.
   5. Specify old .sap file that was generated from the above .fud file. The root of the name of the .fud file will be offered as a default name for the .sap file. Normally some characters will have been appended to that name, specifying for example the mesh resolution used by Fud in generating the .sap file.
   6. Specify name for new .sap file. The default that is offered is the name of the old .sap file with ‘z’ appended.
   7. Specify threshold value for z. Nodes are flagged if they are assigned a z value greater than the threshold. This is done in order to identify mesh nodes which lie outside the region of valid moiré-based z values. Flagged nodes will be displayed in red, and the rest in green, then the threshold value will be requested again. This will be repeated until the same threshold value is specified twice in a row.
   8. FileExit
7. Examine the mesh using Fad.
8. Possibly modify the mesh.
9. Use finite-element software to do the simulation.
10. Use Fod to examine the simulation results.

The boundary of a flexible object like the eardrum can be precisely located by combining shape profiles obtained with varying applied pressures. See our 1996 article for a description of the use of Mum for eardrum modelling.

Mum is implemented in Fortran. It is currently being developed under Debian GNU/Linux (amd64 and i386) and (alas) Microsoft Windows. The binary is available GNU/Linux by request; the binary for Windows is offered here (but may not always be up to date).

Mum can be used for any purpose as long as I am informed of its use. So far there is no documentation beyond what you're looking at.

Installation under MS Windows

Either download the Mum executable for 32-bit Windows (about 1.7 Mbytes) or (if your computer is part of the McGill BME network) create a shortcut to the executable on probeShare. Follow the general instructions for installation of Dip software.