# 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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### What is the intended behaviour when transforming normals with view matrix

I am writing a basic rasterizer and I'm testing to see if my normals are set up and handled properly by shading a sphere with its vertex normals to obtain For context, we are looking in the +Z ...
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### Pose representation using rigid transformations

In literature (3D graphics, computer vision, 3d deep learning etc.) I notice that often an object's pose is represented using a rigid transformation, i.e a member of the group SE(3) combining a ...
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### Automating equirectangular horizon detection in 360 images

I would like to programatically identify pitch and roll numbers that will level the horizon on each frame in a series of equirectangular 360 panorama images. Here's why. I recently ended up with a ...
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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 ...
1 vote
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### 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 ...
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### How to determine the transformation matrix from given initial and transformed co-ordinates?

How to determine transformation matrix for an object given a graph? This is a problem indeed similar to this one. And I've approached it in the same way like there. Given: A line AB A(0,0),B(1,1). It ...
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### 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 ...
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### Create a tight frustum around a 3D model bounding volume

Tight frustum I intend to create a tight frustum around a 3D model: I have these variables: Inputs: 3D model bounding box or bounding sphere or bounding volume. To be determined: Eye distance and ...
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### 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 ...
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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): ...
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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 ...
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### Avoiding gimbal lock in spherical movement around an object - Python

I am programming a camera viewer in Python to move around an object on a sphere given YPR Euler angles (intrinsic) from the user. Everything seemed nice until I pitched the camera 90 degrees up/down. ...
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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)...
1 vote
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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 ...
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### Rendering light balls: Where to do perspective calculations?

After rewatching Bisqwit's starfield renderer video, I've decided to try to rewrite the program in order to learn more about compute shaders and shader programming in general. My knowledge at this ...
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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?
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### Converting points, vectors, normals between world and object space for a ray tracer gives weird results

I'm writing a ray tracer but having trouble converting rays and normals between world space and object space. I am creating a Ray, then transforming it with transformation matrices, calculating ...
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### How to apply transformation matrices from multiple primitives on a mesh

I'm working on some code to convert a 3d geometry from IFC to gltf/glb. One of the challenges I'm facing with this is that - IFC provides transformations for each primitive separately i.e., if I have ...
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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 ...
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### How to apply a linear transformation to gltf data

I am trying to transform the mesh data in a gltf file and then modify the skin and animation data accordingly. Let's say we want to transform the data using a 4x4 homogeneous matrix. For ...
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### OpenGL - How to increase view space coordinate range in X and Y axis

I'm trying to render some objects but apparently X and Y coordinates need to be really small in-order to get something on screen. See this example of 2 lines The world space coordinates for these ...
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### Translation from object space to the world space

I’m stuyding computer animation with this book, Computer animation by The Morgan Kaufmann series. The explanation for translation from object space to world space is difficult to understand. In more ...
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### 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 ...
1 vote
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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)...
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### Confusion surrounding Gimbal Lock

I'm having difficult understanding the issue with gimbal lock, namely why so many diagrams show an aircraft in apparent gimbal lock unable to turn about an axis conventionally, using yaw/pitch/roll. ...
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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 ...
1 vote
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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: ...
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### 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 ...
1 vote
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### How to determine transformation matrix for an object given a graph?

I am given this image: and asked to determine the transformation matrix that took me from ΑΒΓΔΕ(let's call it ABCDE for convenience) to Α'Β'Γ'Δ'Ε' (A'B'C'D'E'). I am also given the solution, so as to ...
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### Convert one triangle to another in matrix4x4?

The context openGL instances learning. I want to transform a reference triangle to another one. So final goal is to have one triangle and the instance being a transformation of that initial triangle. ...
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### What are viewport transformation matrixes for this coordinate system?

I have a set of vertexes (x, y, z) in normalized device coordinates. Its x, y, and z values are in the range (-1, 1). Normalized device coordinates use the left-handed coordinate system, as shown ...
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### What is view transformation and model transformation respectively? How do I implement each transformation in simple opengl program?

I want to know what is view transformation, and what is model transformation respectively, and what methods/functions in opengl could be applied to implement each transformation. Just simple ways to ...
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### What fields should a camera class have?

For a good and scalable project structure, what fields would you add to a camera class, apart from its position and orientation? Should I add the near and far planes? Or should that be global, what ...
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### Confused with Coordinate Transformations

I'm studying coordinate transformations from the book Fundamentals Of Computer Graphics - Peter Shirley, Steve Marschner The book first shows It then says: "We call this matrix the frame-to-...
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### How to translate screen coordinates of a 3d point as the viewport size changes assuming camera state remains constant?

Okay, so let's say I have a point in 3d. And I have a camera state. That is, I know the camera position, the camera target and the camera up vector. I am using the perspective projection to get the ...
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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 ...
1 vote
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### How bits transformed into graphics?

recently i started studying computer science and computer graphics, and one question really haunts me. Mby someone can explain this. How bit patterns become translated into (for example ) text. I know ...
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### 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. ...
1 vote
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### 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 ...
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### Can an aspect ratio be shortened to one value, best practise

I want to make a program that, for starters, list all image files in a folder and writes a warning if one dimension is (i.e.) double (2x) the other dimension, regardless of "image orientation&...
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### Difference between 2D and 3D pipeline

2D transformation and viewing: The camera projects the 2D world co-ordinate $(x_w, y_w)$ on its projection plane which co-ordinates $(x_v, y_v)$. 3D transformation and viewing: The camera projects the ...
114 views

### How to Achieve Radial Rendering

I'm making a POV fan and would like to display some simple graphics in real-time on it. I have a working naive solution with OpenGL, but I'm maxing out at 7 fps rending a simple cube on a raspberry pi ...
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### Parallel projection is special case of perspective projection

I synchronized with @David k's first and second answer regarding perspective and parallel projection. From the first question I understand that the image on the screen is typically described in ...
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### Difference between transformation and projection? [closed]

We know that world coordinates $(x_w, y_w)$ transform to viewport coordinates $(x_v, y_v)$ which are the physical device coordinates. And during projection, any point $(x, y, z)$ projects to $(x, y)$ ...
1 vote
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 ...