# calculate-surface-spectrum¶

## Synopsis¶

calculate-surface-spectrum <input> <output> [options]
calculate-surface-spectrum <input1> <input2> <output1> <output2> [options]


## Description¶

Performs a spectral analysis of the general graph Laplacian matrix computed from the given input surface mesh(es).

If calculate-surface-spectrum -target surface is specified, the eigenvectors are reordered and their sign flipped to match the eigenvectors of the target surface mesh.

If two input and output surface meshes are specified, a spectral analysis of the joint graph Laplacian is performed after an initial surface match. The type of initial point correspondences is defined by calculate-surface-spectrum -corr.

The implementation is based on the MATLAB code by Herve Lombaert of [1].

 [1] H. Lombaert, J. Sporring, and K. Siddiqi. Diffeomorphic Spectral Matching of Cortical Surfaces. In the 23rd Image Processing in Medical Imaging (IPMI), 2013.

## Arguments¶

input

File name of input surface (vtkPolyData).

output

File name of output surface (vtkPolyData).

## Command options¶

-target <file>

File name of dataset (vtkPolyData) whose spectral components should be used to adjust the sign and order of the eigenmodes.

-corr <string>

Type of point correspondences to use for initial correspondences: “closest point” (“CP”), “spectral match” (“SM”). (default: SM)

-corrpar <name>=<value>

Name/value pair of correspondence parameter.

-corrin <file>

Text file naming for each point in input1 the index of the corresponding point in the second dataset input2, one index per line. (default: -corr)

-points

Replace output vertex coordinates by first three spectral coordinates.

## Standard options¶

-v, -verbose [n]

Increase/Set verbosity of output messages. (default: 0)

-debug [level]

Increase/Set debug level for output of intermediate results. (default: 0)

-version [major.minor]

Print version and exit or set version to emulate.

-revision

Print revision (or version) number only and exit.

-h, -help

Print help and exit.

## Terminal options¶

-color, -nocolor

Enable/disable colored output. (default: off)

## Parallelization options¶

-threads <n>

Use maximal <n> threads for parallel execution. (default: automatic)