Questions tagged [transformations]

Transformations are mathematical operations that can be applied to an object to change its scale, position and orientation.

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OpenSCAD Hull/Minkowski function by hand?

I am trying to model an organic object using OpenSCAD. However this will need to be ported over to older software. This restricts the primitives I can use (only cone, cylinder, torus, sphere and cubes)...
RCountZero's user avatar
4 votes
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221 views

Creating an Object Orientated Bounding Volume

I'm attempting to test out the maths behind bounding volume algorithms (prior to ray tracing) using MATLAB. So far, I have successfully created the relatively trivial axis aligned bounding volume, ...
davidhood2's user avatar
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Non Uniform Scaling vs Shear in Image Transformation

I am reading computer graphics. I am unable to distinguish between Non-uniform Scaling and Shear. Can someone explain the difference with two different examples?
Kumar's user avatar
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Linear bending of a mesh

I am trying to implement linear bending of a mesh by following what Alan H. Barr explained in his Global and local deformations of solid primitives paper (ACM link, Direct Link hosted on a faculty ...
Ace Trevis's user avatar
3 votes
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215 views

Calculate Camera parameters and HandEyeCalibration

I'm trying to calculate camera paramters and a hand eye calibration (Transformation from camera to eye (display) coordinates) for rendering on a see-through HMD. I have already calculated a ...
user2479595's user avatar
3 votes
1 answer
511 views

A question about derivation in oblique view frustum

Problem Description: Reference: Oblique View Frustum Depth Projection and Clipping "Mathematics for 3D Game Programming and Computer Graphics" 3rd edition, chapter 5.6. M is the original projection ...
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2 votes
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Finding Camera projection matrix from known input and output

Lets say I have a rectangle with known coordinates in 3D scene, and I'm projecting it using pin point camera to the plane (screen). You can imagine it deforms on the screen per camera transformation ...
Eduard Kovalets's user avatar
2 votes
1 answer
202 views

View rotation matrix

Im unsure about how I could describe what im trying to achieve in few words or a title so ill go on to describe it. So I have voxel, in 3D space, represented solely by its center. The voxel though, is ...
kaelundeen's user avatar
2 votes
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Transforming arcs and perspective change

I have a SVG with group of independent arcs that move around common origin. On user event those arcs can change both their radii and start/end angles. On other user event the user can change view from ...
mtx's user avatar
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preserving z-values during projection?

Consider this figure for projection. There are two equations that give value for the xp and yp coordinates: $x_p=x.\frac{(z_{vp}-z_{prp})}{h}+ x_{prp}.\frac{(z-z_{vp})}{h}$ and $y_p=y.\frac{(z_{vp}...
mathmaniage's user avatar
2 votes
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How can I register an articulated model to noisy predictions?

Given point sets $Y$ and $M$, I'd like to register articulated $M$ to $Y$ without changing the edge distances of $M$. The point correspondences between $Y$ and $M$ are known and points have a fixed ...
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What is wrong with my deformation gradient calculation?

I created two ellipses,$\hspace{150px}$,where the red ellipsis is as the blue one, except translated to the right and rotated by ${30}^{\circ} .$ Using rotation matrix, $$ \left[ \begin{array}{cc} ...
onurtore's user avatar
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110 views

How is it possible to generate geometries using space folding?

There is a TED presentation, where we see really good looking geometries, which are generated using space folding. I get the general idea, that we start from a basic geometry like a cube, and then ...
Iter Ator's user avatar
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With OpenGL, is it correct to apply model transformation to rotate the camera?

Having taken a basic CG course, I remember that transformations are relative, so rotating the camera is identical to rotating the view in the opposite direction. Right now I want to implement camera ...
iksemyonov's user avatar
2 votes
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206 views

Transform a centered isosceles trapezoid in a rectangle in 2-D

I must convert a isosceles trapezoid to a rectangle in 2-D with a shearing transformation (or with 2 shearing transformations). The isosceles trapezoid is centered in the origin of axes. It is right ...
Nick's user avatar
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detect blurred zones after conversion to black & white

I'm working on a document storage project and i found a problem. After converting/compressing a scanned document to black & white sometimes, some areas of the document are unreadable because ...
Daniel Diogo's user avatar
1 vote
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Animation issue using BVH data in OpenGL

I’m currently working on a project involving animation programming using OpenGL and BVH (Biovision Hierarchy) data for animation, and I am trying to get my head around it. I’ve run into some issues ...
blov's user avatar
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Normal Map Under rotation Issue

I have been trying to apply normal maps to a rotating sphere with light shining directing from above the sphere (0,1,0). but lighting does not look correct under rotation as one side of the sphere ...
Sina Dasht's user avatar
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Perlin noise is mysteriously ignored when the pattern is rotated 45 degrees

I am creating different coloring patterns for my CPU raytracer, such as checker, gradient, ring, stripe pattern etc. The problems started when I tried to create a perturbation pattern (of a subpattern)...
Ave Milia's user avatar
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Understanding camera of a CPU raytracer from "Ray tracer challenge"

I am following a book "Ray tracer challenge" by Buck, but it doesn't explain anything. The code works, but I don't properly understand, why. The code is as follows: ...
Ave Milia's user avatar
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Raytracing and transformation

So I'm looking at incorporating instancing to my ray tracer. However what I would like some insight on is what to apply the transformation to?. Most suggest to apply the inverse transformation to the ...
Sina Dasht's user avatar
1 vote
1 answer
275 views

Receiver plane depth bias - matrix explanation / derivation

This source on slide 38 on receiver plane depth bias I can find compute a matrix (Jacobian of screen space uv derivatives) which is used to transform the screen space depth derivatives from screen ...
cg_guy420's user avatar
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Proprietary 3D Format Reverse Engineering: What Could These Numbers And Matrices Represent?

I'm trying to reverse engineer a model format from an older Russian game (Pathologic) with limited success. It is a proprietary model format not recognized by any converters/editing tools (believe me, ...
Xtal44's user avatar
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240 views

Model View Projection Matrix Multiplcation Order

I'm working on a simple software renderer and have a working implementation so far. I'm curious as to why it's actually working since I would expect the multiplication ordering for my world, view and ...
user13873040's user avatar
1 vote
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What's the name of the transformation that can remove horizontal convergence from a picture?

Say that you are taking pictures from a street like this one: As you can see, the picture is taken perpendicular to the direction of the street. The problem is that cars at the left look as if they ...
Lay González's user avatar
1 vote
0 answers
90 views

Why does my self-written rendering engine make further away objects look larger?

I am writing a very simple rendering engine. I have already made a few tests, but somehow the images it creates look wrong. Objects that are further away from the camera look larger than objects ...
HerpDerpington's user avatar
1 vote
0 answers
240 views

Apply transformation to single vertices in OpenGL in order to deform mesh

I'm making a 2D cell simulation game. The mesh for my cell is basically just a manually-generated triangle fan that looks like this. I would like to reproduce the wobbling/vibration effect on the ...
Lorenzo Notaro's user avatar
1 vote
0 answers
561 views

Help with understanding the look-at function (the view matrix)

I've been reading this article about the look-at function. I don't understand the part when they're trying to inverse the matrix N. They say that R is orthogonal because all its row and column ...
tralf_strues's user avatar
1 vote
0 answers
484 views

How to apply scale, translate, rotate with different origin and get new rectangle coordinates

I was reading other questions in this topic but I couldn't apply any viable solution to solve my use case. I have a crop area described with two dimensions (cropWidth, cropHeight) I can easly compute ...
Jacek Pudysz's user avatar
1 vote
0 answers
3k views

General fixed-point scaling

For general fixed-point scaling problem, If I want to scale twice about a fixed point (x, y), I need to first translate the object so that fixed point coincides with the origin, then do the scaling ...
Krash's user avatar
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Octahedral mapping for Spherical functions

I guess most of you are familiar with environment maps, they represent distant lighting distribution, and are used to render objects given their BRDF or SVBRDF distribution. Many papers map the ...
Aditya's user avatar
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Composition of an .obj file

Using an iPhone X, I can get a mesh of the face (using ARFaceGeometry), which I can output as an .obj file using ...
coco's user avatar
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Do Euler Angles always cause Gimbal Lock?

I am learning about euler angles, and read about gimbal lock. I read that representing rotations with euler angles can always cause gimbal lock. All the examples that I saw on the internet show an ...
Mykhailo Seniutovych's user avatar
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10 views

How to morph a enclosing mesh according to the enclosed mesh?

I am quite new to meshing and mesh manipulation. I am working on a problem consiting of meshes $A$, $B$, and $C$. The mesh $C$ completely encloses the meshes $A$ and $B$ as shown in the attached ...
Prakhar's user avatar
0 votes
1 answer
69 views

How apply 3d transformations on 3d Mesh vertcies

I have This 3D mesh class , I use helixToolKit SharpDX to display the mesh and transformations , but i want to apply these transformations to the vertcies dirctly so the mesh can be exported with ...
ahmed moussa's user avatar
0 votes
1 answer
83 views

Pre and Post Multiplication World Space Transform Matrix ambiguity

I'm currently studying about world space transformation matrices and encountered some confusion regarding their application in different matrix orders (row major vs column major). Context In row major ...
makra's user avatar
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0 answers
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4x4 matrix to scale only one axis depending on another axis

I am trying to scale the value of the input vector along one axis depending on the value of the input vector along another axis, while leaving everything else unchanged. Given (pseudocode): ...
Beta Carotin's user avatar
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0 answers
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Computer Graphics Previous Year Question asked in UGC NET 2021

What is the transformation matrix M that transforms a square in the x-y plane defined by (1, 1)T (-1, 1)T (-1, -1)T (1, -1)T to a parallelogram whose corresponding vertices are (2, 1)T (0,1)T (-2, -1)...
Rajesh Prajapati's user avatar
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0 answers
18 views

How can I generate a reflectance map using a perspective camera?

In simple words, a reflectance map is a function f(n) that map a surface patch with normal n to its reflected radiance given a ...
Zhe Chen's user avatar
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0 answers
111 views

Calculating world coordinates of a pixel from a camera picture

Sorry for this question. I know there are many similar questions but I really know nothing about math that involves this case. I have a picture taken from a camera. I know some information about this ...
Magno C's user avatar
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Camera Perspective of 2D X/Y Plane

I'll start with the coordinate system I'm trying to use: If I were standing on the ground, facing north, the x axis is a line moving from the west to the east (positive X is east). Positive y is ...
Helpful's user avatar
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31 views

Is it possible to separate or split original images (or videos) from a blend image (or video)

The title says it all. Blended image or video contains multiple image or video blended on top of each other. I am looking for any software or tools that can separate the original images or videos. ...
Ahmed Abdullah's user avatar
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0 answers
100 views

Help me understand the derivation of this tangent space to object space matrix

I was trying to follow this http://foundationsofgameenginedev.com/FGED2-sample.pdf But had problem understanding formula 7.33. $$p_i-p_j=(u_i-u_j)\mathrm{t}+(v_i-v_j)\mathrm{b}$$ * $p_i,p_j$ being ...
Eugene's user avatar
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3D Bouncing Cube

I'm trying to write a little program with a bouncing cube but I can't find the right x, y, z and angle for it. I have these lines: ...
NeedSomeHeelp's user avatar
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0 answers
318 views

Matrix transforming with translation/rotation/scale at center of screen

I'm trying to create a camera using matrix transforms, the gist as follows: ...
Pooper's user avatar
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0 answers
68 views

How to transform x-y-z red-green-blue arrows and draw them on 2D screen?

I'm making a raytracer and want to print debug arrows Blender example: Old version of 3d max: How do I do the same having camera forward, up and right vector? I think I need some kind of matrix ...
IC_'s user avatar
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0 answers
91 views

Consistent Video Depth Estimation from Monocular Lens to approximate LiDAR?

If the iPhone had LiDAR sensors, it would be possible to generate a 3D point cloud that you could theoretically use to furnish a 3D AR reconstruction of your surroundings. E.g. you could create an AR ...
Sergio Charles's user avatar
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 (...
GreatDuke's user avatar
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0 answers
108 views

Estimate 3D cube pose after camera rotation

I have some photos of 3D cube. I also know the 3D pose of the cube in each photo (yaw, pitch, roll). I want to estimate the new pose (yaw, pitch, roll) of the cube after performing 2D rotation to the ...
nrofis's user avatar
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Transformation for aligning 3D object with reference frame of 3D turtle graphics

The problem I'm using a 3D extension of the well-known "Turtle graphics" to draw plants. My system works by maintaining a position $\vec{p}$ and three vectors: The heading $\vec{H}$ The "up" ...
Katharina's user avatar
  • 111