Questions tagged [rigid-transformation]
Rigid transformations are mappings from one reference frame to another reference frame in the Euclidean space $\mathbb R^n$. They comprise translation, rotation (and sometimes reflection). More formally, rigid transformation are elements of the matrix Lie group SE($n$), the specially Euclidean group. If reflection is included, these proper rigid transformations are elements of the matrix Lie group E($n$), the Euclidean group.
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What is the accuracy of SVD in 3d transformations
I have a triangle $x$ with points $x_1,x_2,x_3\in\mathbb{R}^3$ that were measured at one location. The triangle was then transformed to $\bar x$ where the points were measured again as $\bar{x}_1,\bar{...
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0answers
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Rotation Matrix: Finding points given one point and attitude
I am trying to find points on a rotated rigid body. The body is a ship which has devices onboard and an antenna. The ship has done a survey on device coordinates. So, the exact locations of the ...
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1answer
29 views
Subgroups of the group of motions on the plane fixing a point is the conjugate of the group of all orthogonal transformations by translations.
How do I prove that subgroups $O'$ of the group of motions on the plane fixing a point $p$ (say) is the conjugate of the group of all orthogonal transformations by translations i.e. $O' = t_{p}\ O\ {...
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20 views
Finite subgroups of motoins always fix some point on the plane.
Let $G$ be a finite subgroup of the group of motoins $M$ on the plane. Then there exists a point on the plane which is left fixed by every element of $G$.
The proof of this is sketched by our ...
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0answers
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motion of a rigid cube
A rigid cube is in motion. At the time depicted in the figure the face $ABCD$ is vertical, the velocity of vertex $A$ is vertical down with value $v$, the velocity of vertex $C$ is vertical up with ...
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1answer
50 views
why preserving norm is equivalent to preserving inner product in rigid body transformation
Define rigid body motion as following transformation $g$
$$g:\mathbb R^3 \to \mathbb R^3$$
such that
$$|g(v)|=|v|,\forall v \in \mathbb R^3$$
$$g(u) \times g(v) = g(u\times v)$$
according to ...
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0answers
19 views
A slight confusion about a particular step in Euclidean Transformations (Computer Vision)
On page 392 of Computer vision by Simon Prince (http://web4.cs.ucl.ac.uk/staff/s.prince/book/book.pdf), equation 15.2 has the following expression for the Euclidean transformation in homogeneous ...
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1answer
12 views
Prove that there exist exactly two motions which map two line segments of the same length to each other in a Euclidean Frame
Given two line segments $[P,Q]$ and $[P',Q']$ both in 2D Euclidean frames, with both having the same length, i.e. $d(P,Q) = d(P',Q') \gt 0$ , show that there exists exactly two motions such that $T(P) ...
2
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2answers
250 views
Rotation transformation between two frames
My goal is to express the transformation between the black frame F1 and the other one F0 (Green, Red, Violet):
All what I know ...
2
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2answers
46 views
Given a norm, show a map is Affine
So I have this problem:
Let $\|v\|_1=|x|+|y|$ be a norm in the plane, if $v=(x,y)$.
Now I'm asked to show that, if $T: \mathbb R^2 \rightarrow \mathbb R^2 $ satisfies $\|T(v)-T(u)\|_1=\|v-u\|_1$, ...
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2answers
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How to understand the convention of Euler angle?
We have 3 DOF for rotation in 3D space. So to describe an arbitrary rotation, we need to describe its 3 DOF. Euler angle does this by dividing a rotation in 3 steps, first rotate along the Z axis of ...
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2answers
34 views
How to transform points from a plane to a different plane?
I have a plane $\Pi_1$ expressed as $ax+by+cy+d=0$ and a different plane $\Pi_2$ expressed as $ex+fy+gz+h=0$.
I am looking for a transformation which rigidly brings points lying on $\Pi_1$ to points ...
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1answer
25 views
Seeking 3d rotation
I have a 3d rigid body rotation under which the unit vector $(0, 0, 1)$ becomes the unit vector $(n_x, n_y, n_z)$. I need to find what the vector $(w_x, w_y, 0)$ transforms to under that same rotation....
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1answer
37 views
How much do I have to rotate an object around X, Y, Z in order to make it parallel to a line
I have a cone-shape 3D object like this:
I have a line with a normalized direction vector like this:
Normalized vector = (-0.702755, -0.514791, -0.491045)
I ...
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0answers
95 views
SVD - near-zero singular value
I have difficulties to handle singular values close to zero. My SVD implementation $A = U \Sigma V {}^{T}$ performs first an Eigen decomposition of the matrix $A {}^{T} A$. That is done with the QR-...
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0answers
21 views
Convention for the labelling of parameters of the jacobian of rigid body motion
Assuming we have a matrix representing rigid body motion i.e. SE3 matrix as
$$
\begin{bmatrix}
r11 & r12 & r13 & r14 \\
r21 & r22 & r23 & r34 \\
r31 & r32 &...
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1answer
38 views
How to prove that every rigid motion $F:\,\mathbb{R}\to \mathbb{R}$ is 1-to-1? [closed]
A function $F:\,\mathbb{R}\to \mathbb{R}$ is a rigid motion if for all $x,y\in\mathbb{R}$ with $x\neq y$, $\vert x-y\vert = \vert F(x)-F(y)\vert$.
Using this definition of rigid motion, prove that ...
3
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2answers
63 views
Finding the global maximum of sum-of-exponentials
Problem: find $R$ that maximizes the following:
$$f(R) = \sum_{i} k_i \exp^{-y_i^T R x_i}\\
k_i \in \mathbb{R},\; y_i, x_i \in \mathbb{R}^2\\
R \in SO(2)\;\; (\text{i.e. 2D rotation matrix (2x2, ...
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0answers
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Reference request: Rigid body motion
For a long time I have been wondering if there is some reference in which the motion of a rigid motion is systematically studied from a mathematical perspective; i.e., without using the conventional ...
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1answer
62 views
Curvature and rigid movements
I am getting stuck on a problem that should actually be very easy.
Let $\alpha(t)$ be a birregular curve in 3D space, and $M$ a rigid movement. Let's define $\beta = M \circ \alpha $.
The question ...
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1answer
36 views
Element of $\mathfrak{se}(3)$ is a linear/angular velocity pair?
$SE(3)$ represents the special Euclidean group which can be used to describe the position and orientation of a rigid body in 3D space. It can be defined as
$$SE(3)=\{(p,R): R\in SO(3), p\in \mathbb{R}^...
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2answers
311 views
Rotation matrix about any custom axis
I know the rotation matrices about x, y and z axes but what about rotation about any other axis. I mean if I rotate whole coordinate system clockwise about axis (0,0,0) to (1,1,1) through 120 degrees, ...
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1answer
74 views
Points fixed by the isotropy group of the restricted Poincaré group in Minkowski space
What points does the isotropy group $SO(3)$ fix in the Minkowskian case? For instance, in oriented Euclidean 3-space the isotropy group $SO(3)$ of the Euclidean group $E(3)$ fixes the origin. What is ...
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1answer
146 views
Prove that every proper rigid motion in space (R^3) that fixes the origin is a rotation about some axis
I tried to prove this theorem but having hard time to start with. What I have gotten hint is that starting with rigid motion f = La(left multiplication by A) where A is in O(3) (set of all orthogonal ...
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1answer
66 views
Proving that the trace of a plane curve is simetric with respect to its normal vector at $s=0$
Let $b >0$ and $\alpha : (-a, a) \rightarrow \mathbb{R^2}$ be a plane curve parametrized by arc length. Suppose that: $$k(s) = k(-s) \quad \forall s \in (-a,a)$$ where $k(s)$ denotes the curvature ...
1
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1answer
49 views
Calculating relationship between two coordinate frames with known relationships between each coordinate frame and a third one
Suppose I have three coordinate frames, W, D and C.
I will express all translation vectors as $T$ and rotation matrices as $R$, where $T ∈ \Bbb R^3$ and $R ∈ SO(3)$.
I know the translation and ...
1
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0answers
61 views
Minimizing a transformation describing the configuration of a rigid body with respect to its vertices
I am solving a least squares optimization.
I have a 2D rigid polygon, which can be completely described through a rigid transformation $T = \begin{bmatrix} R_\theta &t \\ 0 &1\end{bmatrix}$
...
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0answers
115 views
Metric describing difference between two proper-rigid transformations in 3D
I am estimating a transformation $\hat{T} \in SE(3)$ between two 3-dimensional coordinate systems (COS) $C1, C2$. I know the exact (ground truth) transformation between the two COS, namely $T_{GT} \in ...
2
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1answer
678 views
Rigid motion vs Isometry
Does anyone know the difference between rigid motion and isometry?
In the real plane these two definitions coincide, but do always coincide?
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1answer
75 views
relationship between two planes (or their (N,d) vectors)
I'm reading this article in computer vision and I just can't get my head around eqution(6). The scenario is as follows: We have the pose of a camera in world coordinate system as $T_{w,c}$ so that a ...
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1answer
110 views
Convert 3D rotation and translation to new coordinate system
I am given a $3\times 3$ rotation matrix and a $1\times 3$ translation matrix defined in a coordinate system where $x$ points right, $y$ points forwards, and $z$ points up.
Now I need to describe ...
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0answers
99 views
Derivative of rigid transformation using exponential map
I have been looking into Lie algebra in order to compute an optimization to figure out the rigid transformation of a set of points.
For now, I have calculated the transformation given an axis-angle ...
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1answer
139 views
how to rotate point around a line in 3D
I have a body with origin at point A which is represented in homogeneous coordinate of matrix 4x4 and I would like to rotate it around an arbitrary vector in 3d space. I understand how to rotate the ...
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0answers
80 views
Model of a rigid body in $SE(3)$
$\require{begingroup}\begingroup
\newcommand{\bbeta}{\boldsymbol{\beta}}
\newcommand{\bomega}{\boldsymbol{\omega}}
\newcommand{\bnu}{\boldsymbol{\nu}}
\newcommand{\p}{\boldsymbol{p}}
\newcommand{\R}{\...
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1answer
2k views
Minimum number of points to estimate similarity transformation in 3D
I am studying computer vision and learning about different geometric transformations in 2D and 3D. I understand that the 8-point algorithm requires 8 2D point correspondences to recover the 8 DOF of ...
1
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0answers
34 views
Expressing Euclidean isometries using complex variables
Studying for a final in my Euclidean geometry class and I'm having difficulties understanding how my book/professor explained Euclidean isometries.
He wants us to understand the classification of ...
1
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2answers
2k views
How should the order of application of rotation transformation be interpreted (in PowerPoint)?
For a university assignment, I have a question about rotating a picture in PowerPoint. In PowerPoint, a picture can have four transformations. Rotate right (90°), rotate left (90°), flip horizontally ...
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0answers
20 views
Find optimal orthonormal transformation of functions?
Let $f,g$ be smooth and integrable functions from $\mathbb{R}^d$ to $\mathbb{R}$. Can someone help with mentioning some papers that tell me how to find the optimal rigid transformation $O^*$ such ...
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0answers
110 views
2D Square matrix have 8 isometric transformations, what is the rule for non isometric transformation?
I do not have formal formation in mathematics so excuse me in advance if my question is easy.
Imagine a 2*2 matrix
A = |a b|
|c d|
I was trying to find ...
0
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0answers
364 views
Prove that F is a rigid motion if and only if F is a translation or a reflection.
A function $F: \mathbb{R} \rightarrow \mathbb{R}$ is a
a) $\textbf{rigid motion}$ if for all $x$, there exists $y\in \mathbb{R}$ with $x$ not equaling $y$ such that $|x-y| = |F(x)-F(y)|$;
b) $\...
1
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1answer
65 views
Differentiate linear transformation
Looking at the answer of this question:
Show that the arc length of a curve is invariant under rigid transformation.
I don't understand why if $T$ is linear then
$$(T\circ \gamma)'(t)=T\circ \...
3
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1answer
345 views
Khan Academy Transformation Puzzle
This problem on Khan Academy has me stumped. It is part of the transformation puzzles exercise part 3. As the questions are randomized, here it is:
While solving the previous transformation puzzles, ...
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1answer
109 views
Rotation matrix defined by two Euler angles
I need to find the expressions for $\hat{e_{CX}}$, $\hat{e_{CY}}$ and $\hat{e_{CZ}}$ accordingly to that picture. How can I write a proper axis transformation so I can obtain $\hat{X}$, $\hat{Y}$ and $...
1
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1answer
419 views
Spline interpolation in SE(3)
Given:
a sequence ${A_i}_{i=1}^n$ of elements of the special Euclidean group, $SE(3)$;
a sequence of times ${t_i}_{i=1}^n$, where $t_1 \leq t_2 \leq ... \leq t_n$;
instantaneous body frame velocity ...
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0answers
94 views
Find a rotary reflection in 3D space between two given tetrahedra
My problem is the following:
Given two congruent tetrahedra (same side lengths but not equally oriented), I have to find the symmetry plane, the axis and the angle of a rotary reflection that goes ...
1
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0answers
47 views
Convention when screw has negative displacement and angle
Any rigid body transformation can be expressed as a screw rotation about and translation along an axis. The screw is usually defined by a line (a unit direction and point on the line), a displacement, ...
1
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2answers
700 views
Prove that every rotation is equivalent to two successive reflections (in 3D)
Prove that a rotation about any axis by a finite angle is equivalent to successive reflections in two different planes.
Here's what I tried:
I assumed two reflection planes (passing through the ...
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4answers
99 views
What transformation maps $y=\frac{1}{4}x-2$ to $y=-3x+6$?
What transformation maps $y=\frac{1}{4}x-2$ to $y=-3x+6$?
I have tried many things, rotating around the origin, reflecting about common lines, and nothing seems to work.
Any help is appreciated. ...
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0answers
79 views
Change of variation under rigid coordinate transformation
Suppose I have a functional
$$
E=\int F(y_{1,1},..y_{1,n},y_{2,1}\ldots,y_{n,n})d\boldsymbol{x}\,,
$$
where $\boldsymbol{y}:\mathbb{R}^{n}\to\mathbb{R}^{n},\,\boldsymbol{y}(\boldsymbol{x})=\left(y_{...
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1answer
110 views
2nd order derivative of Lie group SO(3)
In P.4 of this technical report
there is a equation:
\begin{align}
\left.\frac{\partial^{2}}{\partial \omega_{x}\partial\omega_{y}}(\mathbf{R}_{0}\exp\{J(\omega)\}) \right|_{\omega=0}
& = \...
