Questions tagged [affine-transformations]
The affine-transformations tag has no usage guidance.
23
questions
0
votes
1
answer
47
views
Alignment of the plane coordinate system with the square is similarity transformation
I'm reading the book "Multiple View Geometry in Computer Vision" of Hartley and Zisserman. There was something I was unable to understand correctly. Here's the example where K denotes ...
- 3
1
vote
1
answer
85
views
Why shearing coefficients multiplying by y? [closed]
We know that shear is transformation that distorts the shape of the object. Shear relative to X-axis that is $y=0$ line can be written as:
$x'=x+sh_x.y, y'=y$
My question is why $sh_x$ is multiplying ...
user17337
2
votes
1
answer
220
views
$P^2$ vs projection plane
I want to explain what I understood of definition of the two things.
Projection plane:
The general processing steps for modeling and converting a world coordinate description of a scene to
device ...
user17337
2
votes
2
answers
927
views
What is exactly the third component in homogeneous coordinate system?
I was reading the wiki article about homogeneous coordinates , I learned that it has it's advantages when it comes to performing affine transformation, since you can represent it only matrices. But I ...
- 131
0
votes
0
answers
32
views
Does rotating object inside unit cube [-1,1] by homogenous matrix move it outside unit cube
I am just trying to rotate my pointcloud object which is inside the unit cube ([-1,1] in all x,y,z axis). What I did is use the basic rotation matrix from wiki and extend it to homogenuous 4x4 matrix (...
- 111
1
vote
2
answers
484
views
What kind of transformation when the aspect is changed for a rotated shape?
I have a geometric shape (assuming that is a rectangle). I want to rotate it about it geometric center by an angle of 45° and plot the result using matplotlib with an equal aspect ratio, I get ...
- 111
1
vote
2
answers
5k
views
How to convert from Object space into World space (exercise from 3D Math Primer book)
This is not homework. I'm self studying Computer Graphics, using the book "3D Math Primer for Graphics and Game Development" (2nd edition). So there is the exercise 6 in chapter 3 which I can't figure ...
- 145
2
votes
1
answer
237
views
Deciphering Affine/Projective Transformation Code
I've spent about 2 days trying to understand this piece of code (from here) that applies an affine/projective transformation to an image. I will link bits of the code that I'm struggling to understand ...
- 23
1
vote
2
answers
1k
views
How to make a translation relative to the line ax + by + c = 0, affine transformations
(sorry for my english)
The task:
A triangle is specified. To realize its motion on the basis of mirror reflection with respect to an arbitrary line ax + by + c = 0, the coefficients of which are ...
- 13
0
votes
1
answer
110
views
Image warping using pixel normals
I want to insert a logo into an RGB image with proper 3D transformations. I can get the estimated pixel normals of this image using the code here: https://github.com/yindaz/surface_normal. Pixel ...
- 101
5
votes
1
answer
1k
views
why is translating in 3D space the same as shearing in 4D space?
I was reading "3D Math Primer for Computer Graphics and Game Development" and there was something the author had said that I thought was particularly interesting, he stated
It is important to ...
- 51
3
votes
2
answers
1k
views
OpenGL : How to rotate an object around viewing space x-axis
I have an object(cow).
This cow was translated and rotated(with arbitrary axis) in the modeling space for several times.
And I can't know how much cow is translated or rotated.
Only I can obtain is ...
- 61
4
votes
1
answer
441
views
Why does an affine transform work only on three of the corners?
I am trying to use a linear transformation to straighten out the camera angle on this image:
In other words, I want to transform the image into a head-on view of the whiteboard.
I applied an affine ...
- 171
2
votes
1
answer
6k
views
OpenGL : How to translate an object with it's own axis
I'm working with OpenGL to try to rotate / translate my 3d object : a cow.
The requirement is simple :
If I toggle key 'r'. The cow spinning around and random axis.
If I drag the cow with mouse, it ...
- 61
1
vote
0
answers
374
views
Applying 3d transformation to cuboid
I have the 8 vertices of a cuboid (red points)(XYZvox) with known distance in millimetres (vox to mm) between each vertex which I transform in 3d space using the 4d transformation matrix (M). I am ...
- 111