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Questions tagged [projection-matrix]

234 questions
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How to draw an object and rotate it in oblique frontal projection

How to draw an object and rotate it in oblique frontal (dimetric) projection properly? An illustration of projection: I've already made a program (Pascal with Graph unit) which does it, but I think that it draws object incorrectly. program…
Artfaith
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How to rotate a cube by its center

I am trying to rotate a "cube" full of little cubes using keyboard which works but not so great. I am struggling with setting the pivot point of rotation to the very center of the big "cube" / world. As you can see on this video, center of front…
Ady96
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OpenGL 2D projection matrix not drawing anything

I am using OpenGL for 2D rendering and would like to use actual pixel coordinates. By this, I mean that I would like (0,0) to be in the top left of the window, and (width,height) to be in the bottom right of the window (where width and height are…
rodit
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How to calculate OpenCV camera projectionMatrix in python

I am trying to calculate projection_matrix using OpenCV 2.4 in Python 2.7 for my camera (I am using ps eye). I need it for cv2.triangulatePoints(). I already did the calibration using cv2.calibrateCamera() (using calibrate.py from OpenCV examples)…
Repminister
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Keystoning with JOGL

I am struggling to apply a projective transformation based on the 4 corners of my display, as followed : My insight is to tune up a bit the projection matrix, by first computing the perspective transformation, and multiplying the matrix by the…
Julien Mazars
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Why does graphics pipeline need mapping to clip coordinates and normalized device coordinates?

On perspective projection, if I use simple projection matrix like: 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1/near 0 , which is just projecting onto the image plane. It can be easily get view space coordinates by discarding and normalizing, I think. If on…
Hyunan Kwon
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3D reconstruction using the projection matrices from the trifocal tensor

I have computed the trifocal tensor and corresponding projection matrices P_0, P_1 and P_2 from line correspondences over 3 views, according to 'Multiple View Geometry by Hartley & Zisserman, 2nd edition', Chapter 16. The computed matrices are: P_0…
takahashi
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Moving the Projection Matrix to a Specific X,Y,Z Point ? OpenGLES 2.0 - iOS

Say I am using the below code to setup a projection view : float aspect = fabsf(self.view.bounds.size.width / self.view.bounds.size.height); GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 4.0f,…
GuybrushThreepwood
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Projection matrix from Unity3D to DirectX

I found this question to perform a transformation between OpenGL and DirectX, but it doesn't seem to be working when performing the same things from Unity3D. I was hoping that there is someone here who knows anything about the differences between an…
Marnix
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Pixel-perfect projection matrix in OpenGL?

I'm using OpenTK and I would like to be able to render polygons and textures pixel perfect when their Z is a certain number, anywhere else in the projection doesn't matter (this is for a UI). Is there a way to set up a projection matrix that does…
user2225102
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OpenGLES adding a projection

I'm started to learn a OpenGLES and currently I'm reading this TUTORIAL I have reached paragraph Adding a Projection and I'm stuck there: // Add to render, right before the call to glViewport CC3GLMatrix *projection = [CC3GLMatrix matrix]; float h =…
iWheelBuy
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How to build the correct projection matrices?

Can someone please tell me how the projection Matrices look like for triangulatePoints? Its not that easy, I found several possible projection Matrices but couldn't figure out by now which one is the right one. If I have KeyPoints from Robust…
user1651460
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Triangulation, from calibrateCameras()s' tvec and rvec

its hard too find exactly the answer to my question, that's why I want to ask it here, even it is poorly explained somewhere else. I try to add the solution in code so that everyone can get back to my results. But first it has to be solved. Its…
user1651460
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Align a camera to a rectangle

We are trying to align our camera in order to see as closest as possible a rectangle(a face of a parallelepiped since we are in 3D). The aspect ratio of the viewport considered here and the rectangle to align do not match. What we do: In our scene…
Mr.Pe
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Homogeneous matrix has eight independent ratios of matrix elements?

I'm reading some paper about computer vision. It looks like a simple fact but I can't understand. It is about homogenous [3x3] matrix that is used for planar projective transformation. And it is said to have eight independent ratios of matrix…
HongAnTC AnAn
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