Questions tagged [geometry]

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Understanding and Resolving Singularities in Stereo Rectification using Multiple View Geometry

I am currently working on implementing a stereo rectification algorithm based on the method described in the book "Multiple View Geometry in Computer Vision (MVG)," specifically in Section ...
Lion Lai's user avatar
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104 views

Understanding difference in rotation and translation

Hi I am a newbie to the field so please don't mind a rookie question. I have read multiple articles and want to ensure my understanding is correct. I have following two images. In the second image, ...
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How to implement interpolation by convolution for rotation of an image by an angle which is not a multiple of 90 degrees?

I know that the usual way to perform rotation of an image is to compute the new pixel coordinates by multiplying with a rotation matrix $ \begin{pmatrix}x_{rot} \\ y_{rot} \end{pmatrix} = \begin{...
SheppLogan's user avatar
2 votes
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Geometric Transformation of Distorted Grid Lines Using Image Processing

If the grid-lines in the image (attached: distort1.jpeg) are distorted and squares in image appears distorted a bit. What would be the best and easy approach to convert them to perfect squares (as ...
Pom's user avatar
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Equation of line in the Homogeneous coordinate system

Given two points P and Q we can convert them to the homogeneous coordinate system, compute their cross product and thus get the ...
Mohit Lamba's user avatar
2 votes
1 answer
87 views

Detecting Intersections of a Ray with a Polygon

As a part of a math essay, I am writing a program that detects intersections of a line that is drawn with a shape that is inputted. For example, in the shape below, The polygon is the input image of ...
Nishka Arora's user avatar
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Finding point height on a cup using OpenCV

Suppose that I want to find the 3D position of a cup with its rotation, with image input like this (this cup can be rotated to point in any direction): Given that I have a bunch of 2D points ...
offchan's user avatar
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The rank of Fundamental Matrix

This question is regarding two view geometry where a point lying in the image plane of the first frame/ position of the camera is mapped onto the image plane of the second frame/ position of the ...
skr's user avatar
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How to get the orientation value of a rotated square?

Suppose we have a square shape rotated by $d$ degrees counterclockwise (or $-d$ degrees clockwise) in a binary image as the following: I'm trying to rotate it by 'Orientation' value of regionprops ...
Abdulkader's user avatar
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1 answer
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Computer Vision - Does implementation of Hough Transform for lines require a loop for angle parameter?

I am trying to understand how Hough Transform is implemented in real world applications. Consider a line with equation: $y = mx + b$ In parametric form, this line can be represented using (d, $\...
skr's user avatar
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Can an untilted perspective of an object be obtained from a 2D image of a tilted object using angular transformations?

I'm trying to make a height estimation algorithm that works in tandem with a bounding box object detector. The object detector can recognise the objects in images taken at pitch/yaw angular offsets. ...
brentnallt's user avatar
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Derivation of range migration algorithm

Problem: In Walter G.Carrara's book on synthetic aperture radar, the equation is presented: $\Phi(K_X, K_R) = -K_XX_t - R_B\sqrt(K_R^2 - K_X^2) +K_RR_S $ (10.30) And this is said to come from ...
matthew's user avatar
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Are there analogues to orthogonal transformations in non-orientable surfaces?

I am working on extremely large, symmetric matrices of counts, and attempting to identify patterns/shapes within them. Wavelets are a popular tool in image processing, and have some nice statistical ...
Lewkrr's user avatar
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Finding angles from an IMU (Quaternions to Eulers)

Greetings and apologies if this has already been answered, but I haven't been able to get a clear answer from looking on Stack Exchange so-far. I have Quaternions coming from two different IMU's ...
Merr's user avatar
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1 answer
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Would it be possible to reconstruct 3d trajectory of ball projectile using only monocular video

Assume ball location on the image frame in each timestamp is given. Would it be possible to reconstruct the ball's 3d trajectory in the camera's coordinate frame? The ball should be able to ...
Alvar Ma's user avatar
5 votes
1 answer
507 views

How to triangulate 2 sources on a 2d plane formed by 4 sensors?

I have 4 sensors capturing signal data. Signal distribution speed is constant and known. I have sensors positions in 3d space. Also, I have an amplitude/frequency decomposition for data received by ...
Blender's user avatar
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2 votes
1 answer
379 views

Subsampling property of wavelet transform

One of the properties I have seen for isotropic tight wavelet frames is $$\sum_{i\in\mathbb{Z}} \left|h(2^i\omega)\right|^2 = 1$$ where $h(\omega)$ is the frequency spectrum of the original wavelet. ...
geometrikal's user avatar
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Algorithm to effectively find perspective transform in motion estimation

I've shot a series of photographs in a sort of stop-motion fashion, and although the camera was mounted on a tripod, there are tiny motions between each two successive photos. After some ...
0__'s user avatar
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2 votes
1 answer
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Why is this projection wrong?

I am trying to figure out why a 3D cube doesn't project in the right place in the image. I start with the camera at origin and the cube centered at (0,0,1) world ...
aledalgrande's user avatar
2 votes
2 answers
2k views

How to generate realistic echo to sounds?

I guess the most straightforward way of adding an artificial echo to a sound signal is to add its time-delayed version to the original signal. However, I am not sure how realistic that would sound ...
user16619's user avatar
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1 answer
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3D point cloud to 2.5D graycale image (metric) [Halcon?]

I have a problem ragarding transferring a point cloud to a 2.5D metric grayscale image (gray value gives depth information). I start with a three channel image of 32bit floats with each pixel ...
e_mka's user avatar
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2 votes
1 answer
5k views

Ground plane estimation from a single image (was: confusion about homography and calibration camera parameters)

I'm new to this multiple view geometry issues and I'm a little bit lost, and some concept are not clear at all. I have a calibrated camera ( = I have distortion coefficents, field of view, and with ...
nkint's user avatar
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3 votes
1 answer
351 views

Ideal Geometric Arrangement of Microphone Array

I'm going to have to give a bit of context for this question to make sense. I am working on a project which includes audio source localisation in 3-D space through TDoA (Time Difference of Arrival - ...
jhc's user avatar
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3 votes
0 answers
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Intuition of Location on the Conic Axis TDOA solution

In an old paper "A New Approach to Geometry of Range Difference Location", there is a mathematical derivation that does not include any mention of the relationship to the underlying problem. In the ...
David Doria's user avatar
14 votes
1 answer
4k views

Automatic Cropping of Arbitrary Shapes

I have an arbitrary shape defined by a binary mask (gray = shape, black = background). I would like to find a largest possible rectangle containing only gray pixels (such rectangle is pictured in ...
Libor's user avatar
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4 votes
7 answers
8k views

Is it always necessary to use two cameras to find the distance between camera and object?

I am working on finding the distance between a camera and an object using image processing. In many places, it's written that we have to use a stereo pair, but my project allows only one camera. ...
swapna's user avatar
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2 votes
1 answer
224 views

Reflection Rotation matrix

I'm doing a rigid body between point clouds using SVD. Sometimes the routine produces an incorrect rotation matrix with a Determinant=-1, ie a reflection matrix. Any idea why ? Is there a valid way ...
Martin Beckett's user avatar
7 votes
1 answer
251 views

Minimization of Essential matrix

A problem in computer vision and 3d reconstruction is getting the camera's intrinsics parameters. A common solution is to use an object in which one knows the measurements of the shape before hand, ...
worbel's user avatar
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