1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
|
/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: $RCSfile: itkVersorTransformOptimizer.cxx,v $
Language: C++
Date: $Date: 2007-03-22 14:29:14 $
Version: $Revision: 1.10 $
Copyright (c) Insight Software Consortium. All rights reserved.
See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notices for more information.
=========================================================================*/
#ifndef _itkVersorTransformOptimizer_txx
#define _itkVersorTransformOptimizer_txx
#include "itkVersorTransformOptimizer.h"
#include "vnl/vnl_quaternion.h"
#include "itkEventObject.h"
namespace itk
{
/**
* Advance one Step following the gradient direction
* This method will be overrided in non-vector spaces
*/
void
VersorTransformOptimizer
::StepAlongGradient( double factor,
const DerivativeType & transformedGradient )
{
const ParametersType & currentPosition = this->GetCurrentPosition();
unsigned int NumberOfParameters = m_CostFunction->GetNumberOfParameters();
// The parameters are assumed to be the right part of the versor
//
VectorType rightPart;
for(unsigned int i=0; i<3; i++)
{
rightPart[i] = currentPosition[i];
}
VersorType currentRotation;
currentRotation.Set( rightPart );
// The gradient indicate the contribution of each one
// of the axis to the direction of highest change in
// the function
VectorType axis;
axis[0] = transformedGradient[0];
axis[1] = transformedGradient[1];
axis[2] = transformedGradient[2];
// gradientRotation is a rotation along the
// versor direction which maximize the
// variation of the cost function in question.
// An additional Exponentiation produce a jump
// of a particular length along the versor gradient
// direction.
VersorType gradientRotation;
gradientRotation.Set( axis, factor * axis.GetNorm() );
//
// Composing the currentRotation with the gradientRotation
// produces the new Rotation versor
//
VersorType newRotation = currentRotation * gradientRotation;
ParametersType newParameters(NumberOfParameters);
newParameters[0] = newRotation.GetX();
newParameters[1] = newRotation.GetY();
newParameters[2] = newRotation.GetZ();
// Optimize the non-versor parameters as the RegularStepGradientDescentOptimizer
for(unsigned int j=3; j<NumberOfParameters; j++)
{
newParameters[j] = currentPosition[j] + transformedGradient[j] * factor;
}
this->SetCurrentPosition( newParameters );
}
} // end namespace itk
#endif
|
