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Warp

Namespace: MATHLIB  ·  Library: Math Library

#include <math/warp.h>

class UTILSLIB::Warp

Thin-plate-spline (Bookstein) 3-D warp that maps source landmarks exactly onto destination landmarks and extends smoothly to the rest of R^3.

Used for non-rigid registration of EEG/MEG sensors and template-to-subject mesh warping.

Thin-plate-spline 3-D warp fitted from landmark correspondences.

src/examples/ex_math/main.cpp
// Landmarks moved by a pure translation: the thin-plate spline must reproduce it exactly
MatrixXf sourceLm(5, 3);
sourceLm << 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1;
const MatrixXf destLm = sourceLm.rowwise() + RowVector3f(0.5f, -0.2f, 0.1f);
MatrixXf vertices(2, 3);
vertices << 0.3f, 0.4f, 0.5f, 0.9f, 0.1f, 0.2f;
Warp warp;
const MatrixXf warped = warp.calculate(sourceLm, destLm, vertices);

Public Methods​

calculate(sLm, dLm, sVert)​

Calculates the TPS Warp of given setup.

Parameters:

  • sLm : const Eigen::MatrixXf & 3D Landmarks of the source geometry.

  • dLm : const Eigen::MatrixXf & 3D Landmarks of the destination geometry.

  • sVert : const Eigen::MatrixXf & Vertices of the source geometry.

Returns:

  • Eigen::MatrixXf — wVert Vertices of the warped destination geometry.

calculate(sLm, dLm, vertList)​

Calculates the TPS Warp of a given setup for a List of vertices.

Parameters:

  • sLm : const Eigen::MatrixXf & 3D Landmarks of the source geometry.

  • dLm : const Eigen::MatrixXf & 3D Landmarks of the destination geometry.

  • vertList : QList< Eigen::MatrixXf > & List of Vertices of the source geometry that are warped to the destination.

readsLm(electrodeFileName)​

Read electrode positions from MRI Database.

Parameters:

  • electrodeFileName : const QString & .txt file of electrodes.

Returns:

  • Eigen::MatrixXf — electrodes Matrix with electrode positions.

readsLm(electrodeFileName)​

Read electrode positions from MRI Database.

Parameters:

  • electrodeFileName : const std::string & .txt file of electrodes.

Returns:

  • Eigen::MatrixXf — electrodes Matrix with electrode positions.

Example​

Used in examples​

ex_math​

Math library on inputs with known answers.

src/examples/ex_math/main.cpp, line 179
const MatrixXf destLm = sourceLm.rowwise() + RowVector3f(0.5f, -0.2f, 0.1f);
MatrixXf vertices(2, 3);
vertices << 0.3f, 0.4f, 0.5f, 0.9f, 0.1f, 0.2f;
Warp warp;
const MatrixXf warped = warp.calculate(sourceLm, destLm, vertices);
const float warpErr = (warped - (vertices.rowwise() + RowVector3f(0.5f, -0.2f, 0.1f))).cwiseAbs().maxCoeff();
ok &= expect(warpErr < 1e-4f, QString("TPS warp reproduces the translation (max error %1)").arg(warpErr));

ex_warp​

Example demonstrating thin-plate-spline (TPS) warping with UTILSLIB::Warp.

src/examples/ex_warp/main.cpp, line 109
// Fit the thin-plate spline from the landmark correspondences and apply it to
// the source vertices in one call.
//
Warp warp;
MatrixXf warpedVert = warp.calculate(sourceLm, destLm, sourceVert);

Authors of this file​