Questions tagged [rotations]

This tag is for questions about *rotations*: a type of rigid motion in a space.

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Is There a Rotationally Invariant Order of Points on the Sphere $S^2$

Question: Let $S^2$ denote the 2-sphere embedded in $\mathbb{R}^3$. Consider the group $SO(3)$ of rotations acting on $S^2$. Is there a strict total order $<$ on the point set $P\subseteq S^2, \...
Eddie Lin's user avatar
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Point of contact between an ellipse $(5 \cos t , 3 \sin t)$ and an apparent tangent $ x \cos(R) + y \sin(R) =D$ sliding on it.

Let $E$ be an ellipse defined by $ (x^2 / 5^2) + ( y^2 / 3^2) = 1 $ or, equivalently $( 5\cos t , 3\sin t )$ with $0\leq t \leq 2 \pi$. Let $P= ( 5 \cos R , 3 \sin R) \space 0\leq R \leq 2 \pi$ be a ...
Vince Vickler's user avatar
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0 answers
18 views

Find the angle of a higher dimensional rotation matrix

I was trying to find the angle of an arbitrary rotation matrix, and I decided to use the formula for angle between two vectors: $\theta=\max\limits_{\vec{x}}\left(\arccos\left(\frac{\vec{x}\cdot R\vec{...
Xiutecuhtli's user avatar
-3 votes
0 answers
16 views

how to get desired angular velocity with desired so3 rotation matrice?

i was reading "Geometric Tracking Control of a Quadrotor UAV on SE(3)" (available at https://arxiv.org/abs/1411.2986) and i wanted to simulate it in matlab...) the thing is our closed ...
arash mokhtari sherkat's user avatar
5 votes
2 answers
133 views

How do I minimize a function where some of the variables are dependent on other variables?

Consider a camera placed in $(XC,YC,ZC)$. The camera is looking down on a flat table $Z=0$: Introduce a local coordinate system for the camera: $(x,y,z)$. Initially the axes of the local coordinate ...
Andy's user avatar
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Is this equivalence between two ways of expressing the coordinates of a rotated point useful?

Using " matrix by vector" multiplication, one can establish that the coordinates of the image ($P'$) of a point $P=(a,b)$ under a rotation by $\alpha$ radians ( counterclockwise) are : $$ \...
Vince Vickler's user avatar
1 vote
0 answers
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Build a rotation matrix to perform discrete parallel transport on a discrete curve

Consider a discrete cuve with vertices $\{...x_{i-1}, x_i, x_{i+1}, ...\}\in \mathbb{R}^{3n}$, and denote the edge $e^i=x_ix_{i+1} $ and tangent $t_i=x_{i+1} - x_i$. When perform discrete parallel ...
Zihan Zhao's user avatar
5 votes
1 answer
71 views

Extension of Wahba's problem: finding two unknown rotations surrounding a known rotation

Wahba's Problem seeks to find the $3\times3$ rotation matrix which minimises: $$ J(\boldsymbol{\mathrm{R}}) = \frac{1}{2} \sum_{k}|| \boldsymbol{{w}}_k - \boldsymbol{\mathrm{R}}\boldsymbol{v}_k||^2 $$ ...
andrewjohn's user avatar
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Retrieve Roll and Pitch rotation

I need to retrieve Roll and Pitch (but not Yaw) rotation values from rotation matrix (or euler angles, or quaternion, input can be different, fortunately, it can be converted from one form to another)....
Kaneko Qt's user avatar
0 votes
1 answer
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Rotation in cylindrical coordinates and exterior derivative

Suppose a 1-form $A$ of $\mathbb{R}^3$ is represented as $A= A_r (r,\theta,z)dr + A_\theta (r,\theta,z)d\theta + A_z(r,\theta,z)dz$ using cylindrical coordinate system $(r,\theta, z)$. The external ...
tony-c's user avatar
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1 vote
1 answer
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Rotation matrix and orthogonal matrix

If I am given an orthogonal matrix $A$ and I right multiply by $W $ to get $B=AW$ where $W$ is a diagonal matrix then essentially, I am scaling the columns of $A$ by the diagonals of $W$, preserving ...
meatball2000's user avatar
1 vote
2 answers
26 views

How to recover the cartesian equation of a rotated parabola from its parametric equation obtained using linear algebra ( rotation matrix)?

Every point of the $y = x^2$ parabola can be seen as the endpoint of a position vector of the form $< t, t^2>$. So, rotating this curve counterclockwise can be assimilated to applying a linear ...
Vince Vickler's user avatar
1 vote
0 answers
38 views

Validity of this proof for rotation matrices being orthogonal

We were studying vector transformations using matrices and rotation matrices in our physics class and the professor's proof for some rotation matrix $R$ being orthogonal was to take a column vector $A$...
Rajdeep Sindhu's user avatar
1 vote
2 answers
120 views

How to swap the roll and pitch of a quaternion

I'm writing code that receives quaternion values that are used to rotate a $3$D model. To display the model with the correct orientation, though, I'll need to swap the roll and pitch (rotation about ...
Epsilon's user avatar
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1 answer
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Rotations in D dimensions [closed]

So, if we are in $\Bbb R^{n}$ there are $n(n-1)/2$ rotations. Which is to say: Given $1$ of the $n$ axis, we can rotate it onto $n-1$ other axis. We then divide by $2$ to not overcount. That's OK, ...
Matteo's user avatar
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1 answer
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The area of closed curve made by sine functions that are rotated on some angle $\theta$ [closed]

I constructed interesting figure and want to know its function on Cartesian plane and the area enclosed by this figure. Suppose you have the sine function (explicitly, $m \cdot \sin(kx)$) from 0 to $\...
linus's user avatar
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1 answer
50 views

How to see what rotation an orthogonal matrix represents? [closed]

As the output to some calculation I get an orthogonal 2-D matrix, which I know must represent some 2-D rotation (and possibly a reflection). It looks like \begin{bmatrix} f & g \newline 1 & 1 \...
quantum_loser's user avatar
1 vote
2 answers
46 views

Constructing transformation of an extended spherical movement

I have a frame of reference positioned on a surface of a sphere with the $z$-axis always pointing towards the center of this sphere, which is at distance $d$. Now given: spherical angle $\phi$ ...
garma's user avatar
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0 answers
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Matrix Vector multiplication of Gaussian Matrix and Gaussian Vector

I am curious about how $y$ is distributed if: $$y=Ax,$$ with Gaussian Matrix $A \in \mathbb{R}^{m \times n}$, every entry of the matrix $e_{ij} \sim N(0, 1)$ and Gaussian Vector $x \in R^n, \mathbb E(...
anonymousMonkey's user avatar
0 votes
0 answers
30 views

Convert angle to value and value to angle

I have an "arc" react component and I'm struggling with the math to convert the angle (in degrees) to a value, and the value to an angle. This arc has a "handle" which represents a ...
Shannon Hochkins's user avatar
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0 answers
25 views

Relation between quaternions, Pauli vectors and regular vectors

I'm learning about rotations in 3D space. I've come across Pauli vectors and quaternions. Now as I understand, one can associate to a regular vector $\vec{v} = (v_x, v_y, v_z)$ a Pauli vector and a ...
Luke__'s user avatar
  • 173
3 votes
2 answers
62 views

Geometry question: equidistant center point of 45-45-90 triangle

Okay, I've been struggling on this for a couple days now. Given a 45-45-90 triangle with legs of length n, extend three perpendicular rays, one from each segment, such that they intersect within the ...
NerdyDeeds's user avatar
2 votes
0 answers
39 views

How to generate evenly spaced rotations in SO(3) and/or a regular grid over $\mathbb{S}^3$ (to be used to divide the space of unitary quaternions)?

I am trying to split the space of $\mathrm{SO}(3)$ into spaces $(S_i)_{i\in\{1, \cdots, n\}}$ of rotations providing a regular paving of $\mathrm{SO}(3)$. At least I would need that $\bigcup_{i=1}^n ...
tarta's user avatar
  • 21
1 vote
0 answers
29 views

Sigma matrices and quaternion correspondence

I'm trying to learn the mathematics behind spinors and I've come across sigma matrices and quaternions, both used to describe 3D rotations. Now it is possible to notice that any squared pair of sigma ...
Luke__'s user avatar
  • 173
2 votes
3 answers
242 views

Solving for the rotor in quaternion rotation

If we have 2 vectors $v_1,v_2$ which have been rotated into $v'_1,v'_2$ by the following operations: $v'_1 = e^{θ\hat{n}/2}v_1e^{-θ\hat{n}/2}$ $v'_2 = e^{θ\hat{n}/2}v_2e^{-θ\hat{n}/2}$ Where $\hat{n}$ ...
George Chiporikov's user avatar
3 votes
0 answers
102 views

I need a rigorous explanation of Shoemake method to sample uniformly from the group of unit quaternions

I know and understand the subgroup algorithm to sample from uniform distribution on the rotation group $SO\left( 3 \right)$, following the following steps: sample $\theta_{1}$ from $\text{Unif}\left[ ...
petem's user avatar
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1 vote
1 answer
33 views

Quaternion kinematics transition matrix closed form

For rigid body rotation discrete time kinematics equation is as follows $R_{k+1} = T_r \cdot R_k$ where: $R$ is a rotation matrix $T_r = e^{-[a\times]}$ is a transition matrix $[a\times]$ means a skew ...
aliko's user avatar
  • 143
0 votes
1 answer
55 views

Rotation of an object in 3D

I want to rotate a 3D object using a python code. After doing some search, I was able to come up with the following initial steps: Input the Euler axis, input the Euler angle of rotation, Normalize ...
z987's user avatar
  • 1
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0 answers
23 views

Tifr gs 2021: symmetry of coloring chessboard under rotation [duplicate]

Let $\mathcal{C}$ denote the set of colorings of an $8\times 8$ chessboard, where each square is coloredeither black or white. Let $\sim$ denote the equivalence relation on $\mathcal{C}$ defined as ...
user avatar
1 vote
1 answer
57 views

I need an alternative 3d rotation/translation matrix for a pygame visualization.

Rotation around arbitrary axis ...
jlettvin's user avatar
  • 113
0 votes
0 answers
13 views

Relationships in formula of rotation of a plane about a point $(a, b)$ and angle $\theta$

Let $(a, b)$ be a point in $\mathbb{R}^2$ and $\theta$ be an angle of rotation. Using translation and roation matricies, namely $$\begin{pmatrix} 1 & 0 & a \\ 0 & 1 & b \\ 0 & 0 &...
struggling_student's user avatar
2 votes
1 answer
42 views

Combining rotations about different coordinate systems

I'm working on what I imagine is a common problem, but am struggling to find high quality resources. It is easiest to describe with an example: Let's say I have a series of frames and coordinate ...
Andrew Lock's user avatar
0 votes
0 answers
34 views

What convex polygons admit 60 degree rotational symmetry?

I was trying a problem from a contest,i.e rmm that involved these kind of polygons and I tried to find all polygons that admit 60 degree rotational symmetry. I believe intuitive that it has to do with ...
math is cool's user avatar
2 votes
0 answers
31 views

How to calculate angle of rotation given a vector and a point

sorry if the title seems vague. English is not my first language and I dont know what to search to find the answer to my problem. I will preface this by explaining the purpose of this question. I have ...
ibrahim mohamed's user avatar
0 votes
0 answers
28 views

Describe a rotating cube around its axis as a piecewise function

Consider a cube filled with random particles. The cube is rotated around the z-axis through its center, with the rotation being proportional to the height within the cube. At the bottom of the cube, ...
Sami's user avatar
  • 101
1 vote
1 answer
75 views

A single rotation to reach the final pose of a frame

The following question is from Kinematic Analysis of Robot Manipulators by Carl D. Crane, III, Joseph Duffy: "The transformation that relates the A and B coordinate systems is given as That is ...
Ali Kıral's user avatar
0 votes
0 answers
18 views

Vector algebra of points in tangent space of SO(3) plane.

I know that we can perform algebric operations in the so(3) plane. Let us take $R_1,R_2$ and $R_3$ as rotation matrices in SO(3) plane. ^v: vector representation of skew-symmetric matrix. Vector from $...
shiv's user avatar
  • 1
28 votes
9 answers
4k views

Why do complex numbers lend themselves to rotation?

In the introductory complex analysis course I am taking, nearly every theorem relates to rotation and argument. Why do complex numbers love doing this so much? I can understand why these theorems work;...
Christopher Lee's user avatar
0 votes
1 answer
105 views

Replacing a double rotation by a single rotation?

I had a test tonight and there was one problem that I couldn't even think about a solution. Problem was this, as much I can remember: You are doing two rotations. First one from $y$-axis to $z$-axis ...
unit 1991's user avatar
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0 answers
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Formula for Transformation of Polynomial Coefficients under Rotation

I have a function represented in a basis of 2D Legendre polynomials, $$ f(x,y) = \sum_{n=0}^N c_n P_n(x,y) $$ where $P_n(x,y)$ is a 2D Legendre polynomial given by $$ P_n(x,y) = P_l(x)P_m(y) $$ where $...
David G.'s user avatar
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0 votes
1 answer
66 views

Why does $\boldsymbol{\nabla} \times \textbf{E}=\textbf{0}$ imply $\boldsymbol{E_2}^{\parallel}=\boldsymbol{E_1}^{\parallel}$?

I am currently studying 'Introduction to Electromagnetism' by David Griffiths, and I was reading about the electric displacement $\boldsymbol{D}$. I decided to try to extract eq. 4.27, which states: $\...
Rasmus Andersen's user avatar
2 votes
3 answers
106 views

When two perpendicular lines are rotated about each other (out of their common plane), what is the new angle between them?

When two perpendicular lines are rotated about each other (out of their common plane), what is the new angle between them? More formally: Let $\ell, m$ be two perpendicular lines, and let their common ...
SRobertJames's user avatar
  • 2,722
1 vote
1 answer
68 views

Why doesn't converting a difference quaternion to euler angles give angular velocity?

According to https://stackoverflow.com/questions/22157435/difference-between-the-two-quaternions I can get the difference between two quaternions as ...
Rufus's user avatar
  • 185
0 votes
0 answers
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Matrix Representaions of Binary Icosahedral Group's Element

I am wondering how to write rotations of binary icosahedral group as matrices. For example, the identity element of this group corresponds: $R_1 = 1 + 0i + 0j + 0k$ since this group corresponds to ...
j.doe's user avatar
  • 207
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0 answers
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Knowing the equation of the tangent to a rotated curve, how to find the point of tangency.?

Desmos construction : https://www.desmos.com/calculator/uul5rbl6gd Note : in the case of non rotated curves, the coordinates of the point of tangency can be " read off" on the equation of ...
Vince Vickler's user avatar
1 vote
3 answers
111 views

Matrix of rotation in $\mathbb R^{3}$

I'm attempting to teach myself basic multivariable calculus and so far finding some of the 3d visualizations a bit difficult. Here's an example: Let $f: \mathbb R^{3} \longrightarrow \mathbb R^{3}$ be ...
RTF's user avatar
  • 420
2 votes
1 answer
44 views

Generate a randomly-oriented vector $\vec{w}$ at a specific angle $\theta$ from another vector $\vec{v}$ in $\mathbb{R}^n$

I'm currently facing a problem where I need to perturb a provided vector $\vec{v}$ to produce a new vector $\vec{w}$, where both are located in $\mathbb{R}^n$, by perturbing both the magnitude and ...
AstronomyIsMyThang's user avatar
0 votes
0 answers
15 views

"Canonically" rotate a path/trajectory/sequence of points

I have a sequence of $n$ points in $\mathbb{R}^3$: $$P_0, P_1, P_2, \ldots, P_n$$ where $ P_i = (x_i, y_i, z_i).$ We can assume, that they are "centered", i.e. the mass center (average) is ...
Jake B.'s user avatar
  • 421
0 votes
2 answers
54 views

Prove that holomorphic functions preserve their norms under rotations.

I want to prove (or disprove) that any non-constant holomorphic function preserves its absolute value under rotations of its domain. The precise formulation of the problem is as follows: Let $f:\...
Simón Flavio Ibañez's user avatar
0 votes
0 answers
52 views

Algebraically showing 2 quaternions compose a new rotation

I am trying to algebraically prove that multiplying 2 quaternion rotations produces a new quaterion rotation. This is what I have so far: After lots of simplifying, I get here: I see the first term ...
Jas's user avatar
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