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Questions tagged [reverseprojection]

12 questions
79
votes
13 answers

How do I reverse-project 2D points into 3D?

I have 4 2D points in screen-space, and I need to reverse-project them back into 3D space. I know that each of the 4 points is a corner of a 3D-rotated rigid rectangle, and I know the size of the rectangle. How can I get 3D coordinates from this? I…
Joshua Carmody
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11 answers

proportions of a perspective-deformed rectangle

Given a 2d picture of a rectangle distorted by perspective: I know that the shape was originally a rectangle, but I do not know its original size. If I know the pixel coordinates of the corners in this picture, how can I calculate the original…
HugoRune
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2 answers

Reverse-projection 2D points into 3D

Suppose we have a 3D Space with a plane on it with an arbitrary equation: ax+by+cz+d=0 now suppose that we pick 3 random points on that plane: (x0, y0, z0) (x1, y1, z1) (x1, y1, z1) now I have a different point of view(camera) for this plane. I mean…
ehsan baghaki
5
votes
1 answer

reverse perspective projection

I'm using worldview_inverse * (projection_inverse * vector) to transform screen space coordinates into world space coordinates. I assumed that (x,y,1,1) would transform to a point on the far plane, while (x,y,-1,1) transforms to a point on the…
heeen
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5
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5 answers

Inverse 3D (triangle) projection

I have a 3D math problem which I just can't seem to solve. I have data of 3 points. The data is a (2D) coordinate on a plane, floating somewhere in 3D space. I also know the (2D) coordinate of the projection. That results in the following array of…
Pieter Jongsma
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Need some help to understanding the formula

This is pinhole camera model: (I don't get, is there [R t], or (R, t)) This formula is translating the 3d coordinates of the point, to the 2d coordinates of a picture, which is obtained by pinhole camera. Projection drawing: Tilde over vector,…
Userr
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3 answers

Ray intersection with 3D quads in XNA?

So I have successfully made a ray the represents the mouse unprojected into the world, and now I need to check if that ray can intersect with a quad object, here is the code I use to get the ray: public Ray GetMouseRay() { Vector2…
Glen654
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1 answer

Calculate 3D coordinates from 2D Image plane accounting for perspective without direct access to view/projection matrix

First time asking a question on the stack exchange, hopefully this is the right place. I can't seem to develop a close enough approximation algorithm for my situation as I'm not exactly the best in terms of 3D math. I have a 3d environment in which…
Allar
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Inverting projection and modelview matrices to transform mouse click coordinates to world coordinates intersecting the z=0 plane

BACKGROUND Using kivy with openGL and GLU style functions, I have gotten modelview and projection matrices working. The model matrix is not used, so the modelview matrix is just really a transform based upon the location of the camera. # cx,cy,cz…
weemattisnot
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Calculating 3D Coordinate

I have recently been trying to calculate a 3D point out of a mouse position. So far I have this: const D3DXMATRIX* pmatProj = g_Camera.GetProjMatrix(); POINT ptCursor; GetCursorPos( &ptCursor ); ScreenToClient( DXUTGetHWND(), &ptCursor ); //…
Tyson May
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1 answer

How To Calculate a 3D Point from 2D Coordinates?

I have recently run into a predicament involving DirectX11 and the calculation of a 3D coordinate. I wish to convert a mouse coordinate to this 3D coordinate. I wish to have it act similar to Maya or Unity when inserting a polygon model (default…
Tyson May
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How do I reverse-project 2D points on a plane into 3D?

So, I have a plane P. I've got the 3 coordinates of the plane P normal vector n(n1, n2, n3) and I've got the 3 coordinates of a given point A(a1, a2, a3) which belongs to P. So from that, I can easily get the plane equation. Now, if the 3D…
zadamantine
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