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Questions tagged [geometry]

The tag has no usage guidance.

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1answer
69 views

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 ...
0
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1answer
58 views

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, $\...
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0answers
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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. ...
1
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1answer
126 views

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 ...
0
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1answer
24 views

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 ...
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0answers
19 views

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 ...
1
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1answer
48 views

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 ...
6
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1answer
251 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 ...
2
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1answer
201 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. ...
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2answers
682 views

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 ...
2
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1answer
54 views

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 ...
2
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2answers
1k 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 ...
0
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1answer
479 views

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 ...
1
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1answer
4k 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 ...
3
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1answer
290 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 - ...
3
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0answers
55 views

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 ...
13
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1answer
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 ...
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7answers
6k 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. ...
2
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1answer
168 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 ...
7
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1answer
186 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, ...