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Questions tagged [projective-geometry]

Projective geometry is an incidence geometry of colinearity preserving transformations. Its use is widespread in computer graphics, computer vision, image registration, photography, among others. Homogeneous coordinates are commonly used to represent objects (point, lines, planes etc.) in real projective geometry. These are well-known to represent translation, rotation and perspective transformation simply as matrix-vector multiplication.

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Sampling perspective (sub)views from fisheye image

I have a problem trying to select virtual subimages (lets call them ROIs) in a fisheye image which then I want to undistort. I have the fisheye calibration parameters following. Scaramuzza calibration model. What I would like to do is creating an…
ElPotac
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Given a closed convex curve, let a central convex curve circumscribe it, then what is the minimum of B/A?(A and B are their corresponding areas)

I guess the answer is 2, but I cannot prove it. I mean supermum of the minimum B/A among all A. Notice: Central convex curve means the convex curve is symmetric about a point in it, that is, when you rotate the curve 180 degrees about the point, it…
Nan Zhang
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Why use frustum in OpenGL on top of simple projection?

Let's consider, for simplicity, a 3D scene where, after applying model and view matrices, all vertices are inside a cube [-1,-1,-1]...[1,1,1]. Based on the geometry set up shown on the image below, one can come up with a formula for projected…
user1481126
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How to construct camera matrix from known parameters

I wish to project an image taken with a camera for which I know all parameters (focal length, sensor size, X, Y, Z, rotation (omega, phi, kappa) on a 2D plane. I know that I need to construct a camera matrix before being able to do the planar…
Jean-François Bourdon
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Why reprojection error is minimized instead of triangulation error for bundle adjustment?

For bundle adjustment optmization why is reprojection error minimized instead of traingulation error or ray-to-3d point error? Disadvantage with reprojection error is: for perspective camera, its highly dependent on depth of the camera from the…
Niranjan Kotha
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Finding the distance of an object that is able to move

I'm new to computer vision. I'm trying to solve a problem that I find interesting. My goal is take a 2 pictures of an object, that is able to move freely (like a ball). then compare the two pictures, to see if the balls elevation has risen. I've…
Joshua Jones
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Projective Transformation: Find New Pixel Location MATLAB

I am transforming my images using a protective transformation matrix. I get my transformation by doing the following, where a are 4 fixed points, and b are 4 moving points. my_tform = fitgeotrans(a,b,'projective'); I then transform my images…
keyserSoze
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Convert grid of dots in XY plane from camera coordinates to real world coordinates

I am writing a program. I have, say, a grid of dots on a piece of paper. I fix one end and bend the paper toward the screen, giving me a trapezoidal shape from the camera's point of view. I have the (x,y) camera coordinate of each dot. Is there a…
Moano
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Model transformation from transformation between two frames

Given: a) two frames of a moving object and euclidean transformation(rotate + shift) between them which aligns projection of the object on the first frame to its projection on the second frame. b) model transformation matrix for the first frame; c)…
Vitaliy
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How to implement 3d reconstruction algorithms

I have been doing some study on 3d reconstruction from multiple 2d views of late. Most of what i have read focuses on fundamental matrix , epipolar geometry and other theoretical principles of the subject. Let us say that given two images, I know…
Anant Simran Singh
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Why is this projection wrong?

I am tring 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): Then I create a 3D rotation R of 45 degrees around the Y axis: (0.707106781, 0,…
aledalgrande
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OpenCV speed issue

I want to transform many points (whole 720p image would be best) with ~30fps. Right now i just loop through a mask and look for marked pixels. Then i transform every marked pixel to a new frame. Is there any way to speed it up? The code runs on a…
Wurzelsepp
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Make texture fit 4-point polygon/plane with GLScene or OpenGL for Delphi

I am using the latest GLScene trunk for Delphi XE2 and I have worked on a GUI-ish type of project which uses 3D instead of 2D to draw GUI elements on screen. It works, but the graphics placement isn't pixel-perfect for obvious reasons. I have…
xaid
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applying homography on an image and a marked rectangle using imtransform in matlab

I'm trying to apply projective homography on an image and a marked rectangle. My solution works well for all of the affine transformations, but in the case of projective transformations, there's a systematic error that keeps increasing when I run it…
Ali Hassan
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Find transformation matrix between 2 cameras

I'm trying to find the projective transformation between 2 cameras (Kinect RGB and IR) in Matlab, I had read several answers but all of them use OpenCV, by this moment I can find chessboard points in the 2 images (imageRGBPoints, imageIRPoints), and…
Dinl
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