GuidewireSim.MathHelper Class Reference
Inheritance diagram for GuidewireSim.MathHelper:

## Public Member Functions

void | CalculateCylinderPositions (int cylinderCount, Vector3[] spherePositions, Vector3[] cylinderPositions)
Vector3 | MatrixVectorMultiplication (float[,] matrix, Vector3 vector)
BSM.Quaternion | EmbeddedVector (Vector3 vector)
Vector3 | ImaginaryPart (BSM.Quaternion quaternion)
Quaternion | QuaternionConversionFromBSM (BSM.Quaternion bsmQuaternion)
BSM.Quaternion | QuaternionConversionToBSM (Quaternion quaternion)
Vector3 | DiscreteDarbouxVector (BSM.Quaternion orientationOne, BSM.Quaternion orientationTwo, float rodElementLength)
float | DarbouxSignFactor (Vector3 currentDarbouxVector, Vector3 restDarbouxVector)
float | VectorLength (Vector3 vector)
float | QuaternionLength (BSM.Quaternion quaternion)
float | RodElementLengthDeviation (Vector3 particlePositionOne, Vector3 particlePositionTwo, float defaultRodElementLength)
float | StretchConstraintDeviation (Vector3 particlePositionOne, Vector3 particlePositionTwo, BSM.Quaternion orientation, BSM.Quaternion e_3, float rodElementLength, bool logIntermediateResults=false)
float | BendTwistConstraintDeviation (BSM.Quaternion orientationOne, BSM.Quaternion orientationTwo, float rodElementLength, Vector3 discreteRestDarbouxVector, bool logIntermediateResults=false)
float | RodElementLength (Vector3 particlePositionOne, Vector3 particlePositionTwo)
Vector3[][] | UpdateDirectors (int cylinderCount, BSM.Quaternion[] cylinderOrientations, Vector3[][] directors, BSM.Quaternion[] worldSpaceBasis)
BSM.Quaternion | RandomUnitQuaternion ()
float | GetGaussianRandomNumber ()

## Private Member Functions

float | SquaredNorm (Vector3 vector)

## Detailed Description

This class provides various helper methods for calculation.

## Member Function Documentation

## BendTwistConstraintDeviation()

float GuidewireSim.MathHelper.BendTwistConstraintDeviation | ( | BSM.Quaternion | orientationOne,
|  | BSM.Quaternion | orientationTwo,
|  | float | rodElementLength,
|  | Vector3 | discreteRestDarbouxVector,
|  | bool | logIntermediateResults = `false`
| ) |  |

Returns the deviation of the bend twist constraint from zero.

Parameters

  orientationOne | \( q \) of the equation (32).
  orientationTwo | \( u \) of the equation (32).
  rodElementLength | The Rod Element Length between `orientationOne` and `orientationTwo`. Used to calculate \( \mathbb{\Omega} \) of the equation (32).
  discreteRestDarbouxVector | \( \mathbb{\Omega}^0 \) of the equation (32).
  logIntermediateResults | Whether to output several logs that contain intermediate results of the calculation. Default is false.

Returns
  The Deviation of the calculated bend twist constraint and zero.

Note
  Check the Position and Orientation Based Cosserat Rods Paper (2016), equation (32), for more information on the bend twist constraint.

## CalculateCylinderPositions()

void GuidewireSim.MathHelper.CalculateCylinderPositions | ( | int | cylinderCount,
|  | Vector3[] | spherePositions,
|  | Vector3[] | cylinderPositions
| ) |  |

Calculates `cylinderPositions` as the middle points of two adjacent spheres.

Parameters

  cylinderCount | The count of all cylinders of the guidewire. Equals the length of `cylinderOrientationPredictions`.
  spherePositions | The position at the current frame of each sphere.
  cylinderPositions | The position/ center of mass of each cylinder.

Note
  `cylinderPositions` is not marked as an out parameter, since `cylinderPositions` is not initialized in this method, but its values are changed.

## DarbouxSignFactor()

float GuidewireSim.MathHelper.DarbouxSignFactor | ( | Vector3 | currentDarbouxVector,
|  | Vector3 | restDarbouxVector
| ) |  |

Calculates the sign factor of the current discrete Darboux Vector and the rest Darboux Vector of the same orientations.

Note
  Check the Position and Orientation Based Cosserat Rods Paper (2016) for more information on the sign factor.

Parameters

  currentDarbouxVector | The discrete Darboux Vector of two fixed orientations at the current frame.
  restDarbouxVector | The rest Darboux Vector of the same two orientations at frame 0.

Returns
  The Sign Factor between these two entities.

## DiscreteDarbouxVector()

Vector3 GuidewireSim.MathHelper.DiscreteDarbouxVector | ( | BSM.Quaternion | orientationOne,
|  | BSM.Quaternion | orientationTwo,
|  | float | rodElementLength
| ) |  |

Calculates the discrete Darboux Vector of two adjacent orientations `orientationOne`, `orientationTwo`.

Parameters

  orientationOne | The orientation with the lower index, e.g. \( i \).
  orientationTwo | The orientation with the higher index, e.g. \( i + 1 \).
  rodElementLength | The distance between two spheres, also the distance between two orientations.

Returns
  The discrete Darboux Vector between `orientationOne` and `orientationTwo`.

Note
  There is only cylinderCount - 1 many darboux vectors. The i-th Darboux Vector is between orientation i and orientation i+1.

Attention
  The order in which the orientations are entered matters. The Darboux Vector of \( q_1, q_2 \) is not the same as the Darboux Vector of \( q_2, q_1 \).

## EmbeddedVector()

BSM.Quaternion GuidewireSim.MathHelper.EmbeddedVector | ( | Vector3 | vector | ) |

Returns a quaternion that is the embedded vector with scalar part zero.

Example
  \( (x, y, z) \mapsto (x, y, z, 0) \).

Parameters

  vector | The vector to be embedded.

Returns
  The quaternion that is the embedded vector with scalar part zero.

## GetGaussianRandomNumber()

float GuidewireSim.MathHelper.GetGaussianRandomNumber | ( |  | ) |

Provides a sample from \( \mathcal{N}(0,1)\) by using the Marsaglia polar method to transform a uniform distribution to a normal distribution.

Returns
  A sample from \( \mathcal{N}(0,1)\).

Note
  To understand this method, google the Marsaglia polar method. Note that unity does not provide a function to generate a random number following a gaussian distribution.

## ImaginaryPart()

Vector3 GuidewireSim.MathHelper.ImaginaryPart | ( | BSM.Quaternion | quaternion | ) |

Returns the imaginary part of a `quaternion`.

Example
  \( (x, y, z, w) \mapsto (x, y, z) \).

Parameters

  quaternion | The quaternion whose imaginary part to return.

Returns
  The imaginary part of a `quaternion`.

## MatrixVectorMultiplication()

Vector3 GuidewireSim.MathHelper.MatrixVectorMultiplication | ( | float | matrix[,],
|  | Vector3 | vector
| ) |  |

Calculates the multiplication of \( M x \), where \( M \) is the `matrix`, and \( x \) is the `vector` input.

Parameters

  matrix | The matrix to be multiplied with the vector.
  vector | The matrix to be multiplied with the matrix.

Returns
  The multiplication \( M x \).

Requirements:
  `matrix` must be a \( 3 \times 3 \) matrix.

## QuaternionConversionFromBSM()

Quaternion GuidewireSim.MathHelper.QuaternionConversionFromBSM | ( | BSM.Quaternion | bsmQuaternion | ) |

Takes as input a BSM.Quaternion and returns a UnityEngine.Quaternion.

Parameters

  bsmQuaternion | The BSM.Quaternion to be converted.

Returns
  The converted UnityEngine.Quaternion.

## QuaternionConversionToBSM()

BSM.Quaternion GuidewireSim.MathHelper.QuaternionConversionToBSM | ( | Quaternion | quaternion | ) |

Takes as input a UnityEngine.Quaternion and returns a BSM.Quaternion.

Parameters

  bsmQuaternion | The UnityEngine.Quaternion to be converted.

Returns
  The converted BSM.Quaternion.

## QuaternionLength()

float GuidewireSim.MathHelper.QuaternionLength | ( | BSM.Quaternion | quaternion | ) |

Returns the quaternion length of `quaternion`, i.e. \( \sqrt{x^2 + y^2 + z^2 + w^2} \).

Parameters

  quaternion | The quaternion whose length to return.

Returns
  The quaternion length of `quaternion`.

## RandomUnitQuaternion()

BSM.Quaternion GuidewireSim.MathHelper.RandomUnitQuaternion | ( |  | ) |

Provides a random unit quaternion drawn from a gaussian distribution.

Returns
  A random unit quaternion drawn from a gaussian distribution.

Note
  This works by drawing four random, gaussian distributed, numbers, and filling the components of the quaternion with these numbers. Mathematically, this is equal to drawing a quaternion from a gaussian distribution in \( \mathcal{R}^{4} \), since the joint distribution of gaussian samples is again gaussian.

Requirements:
  The length of the drawn quaternion is approximately equal to one.

## RodElementLength()

float GuidewireSim.MathHelper.RodElementLength | ( | Vector3 | particlePositionOne,
|  | Vector3 | particlePositionTwo
| ) |  |

Calculates the rod element length between `particlePositionOne` and `particlePositionTwo`.

Parameters

  particlePositionOne | The first particle of the rod element under consideration.
  particlePositionTwo | The first particle of the rod element under consideration.

Returns
  The rod element length.

## RodElementLengthDeviation()

float GuidewireSim.MathHelper.RodElementLengthDeviation | ( | Vector3 | particlePositionOne,
|  | Vector3 | particlePositionTwo,
|  | float | defaultRodElementLength
| ) |  |

Returns the deviation between the actual distance of `particlePositionOne` and `particlePositionTwo` (current Rod Element Length) and the `defaultRodElementLength`.

Parameters

  particlePositionOne | The first particle under consideration for the rod element length.
  particlePositionTwo | The first particle under consideration for the rod element length.
  defaultRodElementLength | The rod element length at rest state (i.e. frame 0) between these two particles.

Returns
  The deviation between the actual rod element length and the default rod element length.

## SquaredNorm()

float GuidewireSim.MathHelper.SquaredNorm | ( | Vector3 | vector | ) |

private

Returns the squared norm of a `vector`.

Parameters

  vector | The vector whose squared norm to return.

Returns
  The Squared norm of `vector`.

## StretchConstraintDeviation()

float GuidewireSim.MathHelper.StretchConstraintDeviation | ( | Vector3 | particlePositionOne,
|  | Vector3 | particlePositionTwo,
|  | BSM.Quaternion | orientation,
|  | BSM.Quaternion | e_3,
|  | float | rodElementLength,
|  | bool | logIntermediateResults = `false`
| ) |  |

Returns the deviation of the stretch constraint from zero.

Parameters

  particlePositionOne | \( p_1 \) of the equation (31).
  particlePositionTwo | \( p_2 \) of the equation (31).
  orientation | \( q \) of the equation (31).
  e_3 | \( e_3 \) of the equation (31).
  rodElementLength | \( l \) of the equation (31).
  logIntermediateResults | Whether to output several logs that contain intermediate results of the calculation. Default is false.

Returns
  The Deviation of the calculated stretch constraint and zero.

Note
  Check the Position and Orientation Based Cosserat Rods Paper (2016), equation (31), for more information on the stretch constraint.

## UpdateDirectors()

Vector3 [][] GuidewireSim.MathHelper.UpdateDirectors | ( | int | cylinderCount,
|  | BSM.Quaternion[] | cylinderOrientations,
|  | Vector3 | directors[][],
|  | BSM.Quaternion[] | worldSpaceBasis
| ) |  |

Updates all directors of each orientation at the update step of the simulation loop.

Example
  The directors \( d_1, d_2, d_3 \) are calculated as \( d_i = q \cdot e_i \cdot \bar{q} \) for each orientation \( q\), where \( e_i \) is the i-th world space basis vector. In quaternion calculus, this means rotating \( e_i \) by \( q \).

Parameters

  cylinderCount | The count of all cylinders of the guidewire. Equals the length of `cylinderOrientationPredictions`.
  cylinderOrientations | The orientation of each cylinder at its center of mass.
  directors | The orthonormal basis of each orientation element / cylinder, also called directors.
  worldSpaceBasis | The three basis vectors of the world coordinate system.

Returns
  All directors of each orientation.

## VectorLength()

float GuidewireSim.MathHelper.VectorLength | ( | Vector3 | vector | ) |

Returns the vector length of `vector`, i.e. \( \sqrt{x_1^2 + x_2^2 + x_3^2} \) for a three-dimensional vector.

Parameters

  vector | The vector whose length to return.

Returns
  The vector length of `vector`.

The documentation for this class was generated from the following file:

- MathHelper.cs