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 Unpublished doctoral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