Questions tagged [geometric-transform]
The geometric-transform tag has no usage guidance.
119
questions
0
votes
0answers
20 views
Convert function to convex on infinite range, knowing gradient and hessian
Let's take a function $f=sech(x)$ as an example. It is strongly convex in a limited range of $x$.
It is further assumed that:
$f$ is a "black box", $x$ as input ;
output is the value of the ...
1
vote
0answers
35 views
Normal of Translate works in 3d but not 2d [duplicate]
Edit: in light of these links, I suppose I'm beating a dead horse here. Normal is inconsistent, that's not technically a bug, just slightly disappointing
Why doesn&...
1
vote
0answers
35 views
Image Perspective Transformations
I'm trying to detect the license plate in these types of images which may be captured from various perspectives and lighting
I've found it easiest to detect these two points corresponding to the ...
5
votes
2answers
137 views
Hyperbolic tiling of 3d objects
I have created a 3d object using plot3d and want to try and tile it hyperbolicly. It has a hexagonal cross section and it's the hexagons that I want to tile. Is there a way I can take an object and ...
2
votes
0answers
33 views
How to apply GeometricTransformation to ArrayPlot?
In a previous version of Mathematica (maybe version 7), it was possible to use GeometricTransformation on an ArrayPlot. That ...
3
votes
0answers
59 views
Sweep, scale, and rotate implicit 3d region or contour plot along an arbitrary curve
Suppose I have a 3d region or contour that is implicitly defined and has no explicit parameterization. This is easy to plot, as RegionPlot3D and ContourPlot3D allow implicit functions.
But now I want ...
1
vote
1answer
92 views
Is it possible to directly translate or rotate a Graphics or Graphics3D object?
I have seen the documentation for Translate (https://reference.wolfram.com/language/ref/Translate.html), which allows one to translate a graphics primitive (like <...
11
votes
2answers
387 views
Distorting image to ensure consistent vanishing point
Here's Giorgio de Chirico's painting, Ariadne:
The Surrealist artist deliberately broke the rules of geometric perspective, giving the work his characteristic sense of mystery and unease.
What would ...
0
votes
2answers
149 views
Random rotation at a given angle?
I need to generate a random rotation matrix for a given angle $a$. In other words, a random $n\times n$ matrix $A$ such that for any unit-length vector $v$ the following is true.
$$v'Av\le\cos a$$
The ...
2
votes
1answer
74 views
FindGeometricTransform not working properly for a simple problem
I am surprised why FindGeometricTransform is failing to automatically register or align two sets of points that are drawn from a ...
5
votes
1answer
110 views
Nest or fold a series of geometric transforms
I have a requirement to perform a series of GeometricTransformation[]s using the AfineTransform[] function. I use these to set ...
2
votes
2answers
75 views
EulerMatrix with axes other than X, Y an Z
The Mathematica function EulerMatrix[{Alpha, Beta, Gamma},{a,b,c}] gives the Euler matrix for rotation about X, Y and Z axes. Here by choosing the order of a, b and ...
0
votes
1answer
38 views
Affine transform of sparse list (x,y,z) to a region of x^2 + y^2 + z^2 = 1.0
I have list of x,y,z points (somewhat random) that leads to the image shown below:
I am trying to map this data to essentially a sphere shape using an affine transform. My original attempt was to ...
1
vote
1answer
79 views
Visualizing an Affine Matrix
I have a computer graphics program that prints out affine matrices like
...
1
vote
1answer
70 views
How to modify a particular step length in a 3D random walk?
Suppose I simulate a random walk in 3D using AnglePath3D[]:
...
0
votes
0answers
29 views
How to reorient a Sphere[] and associated point based on some arbitrary axis?
Suppose I have a unit Sphere[] sitting at the center {0,0,0}, with a point on its "north pole", like this one:
...
3
votes
1answer
137 views
3
votes
0answers
110 views
Find nearest crop of image within another image
ImageAlign[ref, i] works well when image i is fully contained within the reference image ref,...
0
votes
1answer
80 views
Need help understanding Graphics Translate
I created a star pattern that I was trying to apply to a circle of pentagons, but the Translate had a slight offset, and I don't understand why. When I drew the ...
3
votes
2answers
100 views
Region function of rotated Polyhedron
Is it possible to find the equation of the internal region of a rotated polyhedron? For example, the analytic region for a Dodecahedron is found by:
...
4
votes
2answers
227 views
Why can't an annulus be mapped as a rectangle
The following code is used to map an annulus to a rectangle:
...
asked Mar 19 '20 at 3:50
A little mouse on the pampas
5,1602 gold badges9 silver badges28 bronze badges
8
votes
2answers
647 views
How to visualize a spherical mesh on a squared plane?
I need to visualize the points of a spherical mesh on a squared plane (this question is different than this one, I believe). For instance, let us first generate points ...
0
votes
0answers
47 views
Setting the location of the origin within an image for AffineTransformation
This question is closely related to this one, but slightly different.
I want to perform several AffineTransforms on an image (myImage). For example, here is a ...
2
votes
1answer
88 views
Geometric transform of a plot with legends and title
I'm doing a ternary phase diagram, so I want to plot it in a triangle and not in a square. If I'm doing the transformation with legends it doesn't work, but if I don't put legends it does work. Why ...
1
vote
2answers
263 views
How do you implement metric tensor in Mathematica?
I'm trying to follow several tutorials on metric tensors. One of the common exercises is a polar metric. I'm stuck trying to implement this in Mathematica. According to the derivation, the polar ...
6
votes
1answer
167 views
Transforming 2D points on to a regular grid or lattice
I have a set of points in 2D generated by doing a DimensionReduce on a list of colors:
...
1
vote
1answer
78 views
Apply non-linear transformation to graphics object
I would like to define some simple geometric primitives (e.g. points and lines) and see what happens when I transform them by a non-linear transformation (in my case $(x,y)\mapsto (\sqrt x,\sqrt y)$). ...
1
vote
1answer
78 views
Translate (and scale) AnatomyData in three-dimensions
I would like to create a Graphics3D entity consisting of a human eyeball and a complex figure defined elsewhere.
(For a minimal working example, assume that the ...
2
votes
1answer
91 views
Difficulty Displaying an Untransformed and Transformed Graphics3D Object with Show
Update: This bug has been fixed
The bug has been fixed and the code below is working in $Version=12.1.1 for Microsoft Windows (64-bit) (June 19, 2020).
Original ...
2
votes
2answers
137 views
1
vote
1answer
149 views
Rotate a circle in 3D space with RotationTransform
This is related to my confusion over how to combine graphics objects and geometric objects: see Affine transformation of circular arc in 3D.
Why does evaluating the ...
6
votes
3answers
408 views
Affine transformation of circular arc in 3D
Start with a quarter-circle of radius 1 centered at the origin and lying in the $xz$-plane:
arc = ParametricPlot3D[{Cos[t], 0, Sin[t]}, {t, 0, π/2}]
I want to ...
5
votes
2answers
374 views
Removing anomalous points from data
I have two sets of 2d-data points which can be transformed in each other by using a certain transformation function.
The problem is that in both data sets there are points which do not have ...
0
votes
0answers
153 views
Transform a field with derivatives
Given a function of Cartesian coordinates $(x, y)$ in $g(x, y) = \frac{d}{dx}f(x, y)-y\frac{d}{dy}f(x, y)$, I want to transform this expression to polar coordinates $(r,\phi)$. I saw a solution using ...
2
votes
1answer
70 views
How is the error of FindGeometricTransform calculated? [duplicate]
This question has beeen asked here but was not answered.
How is the returned error calculated?
I cannot find any information about this in the documentation of ...
0
votes
1answer
114 views
Transforming a conic to it's standard form
Suppose a conic is given.I need to transform it to standard form.So i tried like this:
...
1
vote
1answer
75 views
Sequential 3D transformations
I have a function s[x,y,z] that assumes a reference of centered at the origin and pointed along the positive z axis. Given two points, I want to rotate and translate that function such that its center ...
2
votes
1answer
133 views
How to draw a “Y” shaped branch in Mathematica?
I want to draw a Y-shaped branch in Mathematica. I am trying to draw a line of length L. In step II, I want to translate to the ending point of the line. Then I want to rotate at an angle of 45 deg to ...
4
votes
3answers
1k views
Drawing the Pursuit curves
I was reading this post on Filling Space with Pursuit Polygons. I didn't really see where the filling was, but found it quite interesting.
Then I saw these pursuit ...
0
votes
1answer
223 views
With equation of vector fields which are in cylindrical polar coordinates, how to plot 3-D vector field? [closed]
I have the equation of vector fields which are in cylindrical polar coordinates. How do I plot 3-D vector field? I never used Mathematica.
Edit2:
...
3
votes
1answer
100 views
What algorithm is used by FindGeometricTransform? [closed]
Can anyone tell me how the operation FindGeometricTransform[pts1, pts2] works (I mean inside logic of the transformation function), or where can I find such an ...
0
votes
0answers
167 views
Eigenvalues not invariant after similarity transformation
I have two examples of matrices that undergo a similarity transformation: a random matrix, and an exclusion-process inspired matrix. The similarity transformation $\sigma$ is given by an $L \times L$ ...
2
votes
3answers
249 views
Computing angle of rotation and scaling factor directly from given transformation matrix
I have a simple 2D transformation matrix performing rotation combined with scaling
\begin{bmatrix}
1 & 1 \\
-1 & 1
\end{bmatrix}
Where the scalar $r$ is multiplied with
\begin{...
4
votes
2answers
254 views
Rotating panels with GeometricTransformation
In the field of architecture, learning to manipulate geometry so comprehensively with Mathematica has been fun. However, I seem to have reached my limits with the following ...
5
votes
4answers
964 views
How to double (or triple) each element of equation?
x^2/3+y^2/9==1
(0.5x)^2/3+(0.5*y)^2/9==1
Looks at above two equation,I multiply 0.5 to each element of second equation,which means when plotting, each point ...
2
votes
1answer
439 views
rotate image around fixed point
How can I painlessly rotate a tiff image by some small angle around a point with specific coordinates? The image shouldn't be altered otherwise, it can be padded with zeros if necessary, and then ...
5
votes
1answer
491 views
How to transform general Ellipsoid into rotated axis-oriented one?
Recently, I discovered a long-standing bug in the rendering of Disk and Circle primitives after applying ...
13
votes
2answers
249 views
Why BoundingRegion does not work well?
Bug introduced in 8 or earlier and fixed in 12.0.0
The underlying bug is unstable and wrong rendering of Disk[] and Circle[] ...
1
vote
2answers
370 views
How to determine roll pitch and yaw/Euler angles from approximately orthogonal matrix?
I have a collection of rigid bodies, each comprising ~100 particles. Each body is defined by a list of points corresponding to the coordinates of its constituent particles. The rigid bodies are ...
2
votes
0answers
62 views
How to get explicit result of geometric transformation? [duplicate]
Seems like this simply rectangle rescale should work and return the exact coordinates of the transformed resulting rectangle (which should be ...
