PCA in PCL

/////////////////////////////////////////////////////////////////////////////////////////
template bool
pcl::PCA::initCompute ()
{
  if(!Base::initCompute ())
  {
    PCL_THROW_EXCEPTION (InitFailedException, "[pcl::PCA::initCompute] failed");
    return (false);
  }
  if(indices_->size () < 3)
  {
    PCL_THROW_EXCEPTION (InitFailedException, "[pcl::PCA::initCompute] number of points < 3");
    return (false);
  }

  // Compute mean
  mean_ = Eigen::Vector4f::Zero ();
  compute3DCentroid (*input_, *indices_, mean_);
  // Compute demeanished cloud
  Eigen::MatrixXf cloud_demean;
  demeanPointCloud (*input_, *indices_, mean_, cloud_demean);
  assert (cloud_demean.cols () == int (indices_->size ()));
  // Compute the product cloud_demean * cloud_demean^T
  Eigen::Matrix3f alpha = cloud_demean.topRows<3> () * cloud_demean.topRows<3> ().transpose ();

  // Compute eigen vectors and values
  Eigen::SelfAdjointEigenSolver evd (alpha);
  // Organize eigenvectors and eigenvalues in ascendent order
  for (int i = 0; i < 3; ++i)
  {
    eigenvalues_[i] = evd.eigenvalues () [2-i];
    eigenvectors_.col (i) = evd.eigenvectors ().col (2-i);
  }
  // If not basis only then compute the coefficients

  if (!basis_only_)
    coefficients_ = eigenvectors_.transpose() * cloud_demean.topRows<3> ();
  compute_done_ = true;
  return (true);
}



from /opt/ros/fuerte/include/pcl-1.5/pcl/common/impl/pca.hpp

생각대로

저렇게 긍정적으로 생각해야겠지? 

Z-Y-X Euler Angles

Z-Y-X Euler Angles

Z-Y-X Euler Angles (or X-Y-Z fixed angles)
Rx'y'z' (a,b,c) =

[ cos(a)*cos(b), cos(a)*sin(b)*sin(c) - cos(c)*sin(a), sin(a)*sin(c) + cos(a)*cos(c)*sin(b)]
[ cos(b)*sin(a), cos(a)*cos(c) + sin(a)*sin(b)*sin(c), cos(c)*sin(a)*sin(b) - cos(a)*sin(c)]
[       -sin(b),                        cos(b)*sin(c),                        cos(b)*cos(c)]



X-Y-Z Euler Angles
Rz'y'x' (a,b,c) =

[                        cos(b)*cos(c),                       -cos(b)*sin(c),         sin(b)]
[ cos(a)*sin(c) + cos(c)*sin(a)*sin(b), cos(a)*cos(c) - sin(a)*sin(b)*sin(c), -cos(b)*sin(a)]
[ sin(a)*sin(c) - cos(a)*cos(c)*sin(b), cos(c)*sin(a) + cos(a)*sin(b)*sin(c),  cos(a)*cos(b)]

Rz'y'x' (c,b,a) =
[                        cos(a)*cos(b),                       -cos(b)*sin(a),         sin(b)]
[ cos(c)*sin(a) + cos(a)*sin(b)*sin(c), cos(a)*cos(c) - sin(a)*sin(b)*sin(c), -cos(b)*sin(c)]
[ sin(a)*sin(c) - cos(a)*cos(c)*sin(b), cos(a)*sin(c) + cos(c)*sin(a)*sin(b),  cos(b)*cos(c)]

Nikola Tesla

“If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.”


― Nikola Tesla

ARCBALL

회전축과 회전각도를 결정하여 회전 Quaternion 을 구해냄.

마우스 입력으로 3차원 회전축과 각도를 어떻게 결정하는지 알면 끝.

현재점과 anchor 점을 결정할 때 2D 입력을 spherical mapping을 사용하여 3D Vector로 mapping.

본 논문 : 

ARCBALL: a user interface for specifying three-dimensional orientation using a mouse
http://dl.acm.org/citation.cfm?id=155312

예쁜 구름

지난 10월초 유럽의 어느 하늘 위. 

#pragma warning(disable : 4244)

#if (_MSC_VER)      
// make microsoft visual studio complain less about double / float conversion.
#pragma warning(disable : 4244)
#endif

ofQuaternion.h 에서 참고

Take Screenshot After Some Delay: gnome-screenshot

$ gnome-screenshot -w -d 2

 -d 2 is used for delaying the screenshot for 2 seconds. So within the 2 seconds, we can make the window which we want to take screenshot as active.

Lifelines

Lifelines of referenced historical figures

꼭지점 필터

솔리드 웍스 작업중에 자꾸 켜지는 꼭지점 필터.

Curvature

Geometry perception 과 관련하여:

Larger curves explored by touching multiple points, whether statically or dynamically, appear to be judged by the difference in local slope at different points of contact (Pont, 1997; Pont, Kappers, & Koenderink, 1999).

from Lederman, Susan J., and Roberta L. Klatzky. "Haptic perception: A tutorial." Attention, Perception, & Psychophysics 71.7 (2009): 1439-1459.

Pont, S. C. (1997). Haptic curvature comparison. Unpublished doctoral

dissertation, Helmholz Instituut, Utrecht.

Pont, S. C., Kappers, A. M. L., & Koenderink, J. J. (1999). Similar mechanisms underlie curvature comparison by static and dynamic touch. Perception & Psychophysics, 61, 874-894.

수요일 알리미

"매번 벌써 수요일인가?" 라는 생각을 하게하는 수요일 알리미. 

myDAQ

좋은 세상이구나~

Eigenvalues of rotation matrix : 0~180 degrees

Eigenvalue의 의미를 보여주는 그래프. y축은 imaginary axis.

추가 1)

When an n×n rotation matrix, Q, does not include −1 as an eigenvalue, so that none of the planar rotations of which it is composed are 180° rotations, then Q+I is an invertible matrix. Most rotation matrices fit this description.

http://en.wikipedia.org/wiki/Rotation_matrix

천불동 계곡

사진기로는 담기 힘들었던 천불동 계곡. 

우리나라를 다시보게 만든다.

잘 보면 사람 얼굴같은 바위

Leap motion

Leap Motion 설치 완료. 두둥

sensor_msgs/JointState - ROS

Raw message definition:

string[] name
float64[] position
float64[] velocity
float64[] effort

# This is a message that holds data to describe the state of a set of torque controlled joints. 
#
# The state of each joint (revolute or prismatic) is defined by:
#  * the position of the joint (rad or m),
#  * the velocity of the joint (rad/s or m/s) and 
#  * the effort that is applied in the joint (Nm or N).
#
# Each joint is uniquely identified by its name
# The header specifies the time at which the joint states were recorded. All the joint states
# in one message have to be recorded at the same time.
#
# This message consists of a multiple arrays, one for each part of the joint state. 
# The goal is to make each of the fields optional. When e.g. your joints have no
# effort associated with them, you can leave the effort array empty. 
#
# All arrays in this message should have the same size, or be empty.
# This is the only way to uniquely associate the joint name with the correct
# states.

from http://www.ros.org/doc/api/sensor_msgs/html/msg/JointState.html

금산

하늘과 너무 잘 어울리는 간판

몇몇 집은 열었지만

 

찾아간 날은 정기휴일 !

 

삼계탕집에서 인삼주가 신기한 도로시

jebns

처음에 jebns가 뭔가 했다.

.....sugar

getGaussianKernel

getGaussianKernel : Returns Gaussian filter coefficients.
getGaussianKernel(int ksize, double sigma, int ktype=CV_64F )

ksize – Aperture size. It should be odd ( \texttt{ksize} \mod 2 = 1 ) and positive.

sigma – Gaussian standard deviation. If it is non-positive, it is computed from ksize as sigma = 0.3*((ksize-1)*0.5 - 1) + 0.8 .

ktype – Type of filter coefficients. It can be CV_32f or CV_64F .

int M = 101;

double sigma = 10;

Mat_ g = getGaussianKernel(M, sigma, CV_64F);

for(int i=0; i

{

double g1 = g(i,0);

Dbg("%f", g1);

}

Mat_ 접근

// more convenient forms of row and element access operators 

    _Tp* operator [](int y);

    const _Tp* operator [](int y) const;

    _Tp& operator ()(int row, int col);

    const _Tp& operator ()(int row, int col) const;

    _Tp& operator ()(Point pt);

    const _Tp& operator ()(Point pt) const;

아래는 http://bytefish.de/blog/opencv/code_snippets/ 에서 가져옴

template

void printMat(const cv::Mat_<_tp>& mat) {

    typedef typename DataType<_tp>::work_type _wTp;

    for(int i = 0; i < mat.rows; i++)

        for(int j=0; j < mat.cols; j++)

            cout << (_wTp) mat(i,j) << " ";

    cout << endl;

}

Typical orbits

회전체 모드해석 수업때 이종원 교수님 강의 중 나온 내용.

Matlab으로 그려본 것.

그림만 봐도 spectrum 해석하기 이전에 분석할 수 있음.

Hypocycloid

(more information : http://mathworld.wolfram.com/Hypocycloid.html)

Hypotrochoid

Epitrochoid

Epitrochoid 와 Hypotrochoid에 대한 추가 문서 : http://www.durangobill.com/Trochoids.html

Matlab code: https://github.com/dalek7/Algorithms/tree/master/Curves/special_plane_curves

귀여운 이모티콘

누가 그렸는지 볼때마다 참 잘했다는 생각이드는 카카오톡 이모티콘

iOS에서 OpenCV 2.4.5 linking

iOS에서 OpenCV 2.4.5 linking 할때 생기는 에러.

std::__1::__vector_base_common::__throw_length_error() const", referenced from:

libc++ .dylib 넣으면 됨.

---------------------------------------------------------------
from http://libcxx.llvm.org/

libc++ is a new implementation of the C++ standard library, targeting C++11.

All of the code in libc++ is dual licensed under the MIT license and the UIUC License (a BSD-like license).

Features and Goals

• Correctness as defined by the C++11 standard.
• Fast execution.
• Minimal memory use.
• Fast compile times.
• ABI compatibility with gcc's libstdc++ for some low-level features such as exception objects, rtti and memory allocation.
• Extensive unit tests.

물수제비..

쿠시야 이 호수 이름이 뭐였지?

Moka Express

뮌헨의 어느 백화점에서 쿠시의 추천으로 구매한 40 유로짜리 Moka Express

색다른 맛의 커피를 느낄수 있을까? ㅎㅎ

나트륨

많이도 먹는구나 ㅎㅎ