Questions tagged [matrix]

A 2D array of numbers, symbols or expressions, arranged in rows and columns. Each row must have the same number of columns. The numbers, symbols or expressions themselves are called elements or entries.

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Setting glOrtho and glViewport so top-left of window has coordinates (0,0)

I haven't used OpenGL for a long time and have trouble setting up a 2D screen where the upper left window coordinates are (0,0) and the width and height of the ...
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Transforming 3d point for depth testing

I have a ray and its direction is (o,d). Multiply it by the model matrix to rotate the model. ...
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How does this 4 by 4 matrix (about 4 points are coplanar) come up with this equation?

I have just begun learning some 3d mathematics and OpenGL (trying to implement skeleton animation). I am stuck here when reading a book(Advanced Methods in Computer Graphics). I understand the first ...
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Efficient calculation of billboard sprite transformations

I'm currently adding a billboard mode to animated sprites and static sprites in my 3D engine. The code below works fine, but I want to know if a more optimized solution exists. I've heard about ...
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OpenTK mouse picking not working

I am creating a game using OpenGL and need a lobby for which I am developing with WPF, C# and OpenTK. For the lobby I need mouse picking functionality on the 3D objects and although there are many ...
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How to convert a list into coordinates in pygame

I'd like to have a map in my pygame game but don't want to waste time moving each individual object in it. To resolve this, I'd like to iterate over a list like this: [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...
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World bending (inception like) implementation from scratch

I'm doing my very first engine in c from scratch as an exercise and I wanted to implement this as an added bonus. However I know 0 about three.js or GLSL and I'm having a really hard time ...
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How do I implement a camera orbit from scratch?

I'm doing my own small game engine from scratch and needed to orbit my camera around about the origin but I have no Idea how to do that. All I can find on the internet is how to use camera properties ...
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Drawing lines of arbitrary thickness and color in 3D space (xna/monogame)

Trying to find a way to do as the title says. I'd accept solutions with or without perspective, meaning the line may remain the same thickness regardless of how close or far it gets from the camera, ...
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Calculating bone transformation matrix for vertex skinning

I have an issue with calculating transformation matrices for animation mesh deformation using glm in c++ I have a class Bone which does the basic calculation which does have a current local position (...
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Animation retargeting: local nodes?

I am re-targeting the animation of my model. In my glb file, I replaced the inverse bind matrices with proper new matrices. Now, when loaded in Blender, I get the model right in rest pose. Bones are ...
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Calculating yaw and pitch angles between up and forward vectors and direction vector

I have a transformation matrix and a direction vector, and am trying to calculate separate yaw, pitch, and roll angles between the matrix and the direction vector. I have already calculated forward, ...
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Understanding matrix transformations for skeletal animation

I am working with Collada and GLTF. Say I have a humanoid with 3 bones with the following hierarchy: B0(root) → B1 → B2. Terminology: bind pose is the same thing ...
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retargeting: Am I on the right track?

I try to retarget the position of a bone in the rest position to adapt it to a different model. The goal is to have my animation properly working for two models from one animation. It is the child ...
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Apply a mocap to multiple different models? -> modify gltf directly?

I am currently struggling with an animation I made that I would like applied to multiple models, all different, but from the same vertices. I already have a custom gltf importer ready but I need to ...
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Why would some assets require a transposed TBN matrix?

I'm writing an OpenGL/DX11 Windows/Linux "engine" and I've encountered a confusing behavior in DX, specifically. For math, I'm using GLM, which means all of my HLSL ...
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Matrix math: How to specify camera distance so that an object with a given size is completely visible?

This is my code that draws a top down view tile based map. But Iam do not know how high the camera needs to be placed in the sky so that the map is fully visible so that nothing is cut away and I do ...
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How to calculate camera view matrix from world transform, specifically the orientation?

In my engine, camera is just any other object in the scene. It has a transform -- position, rotation (quaternion), and scale (ignored for camera view matrix). I want to convert this to the camera's ...
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Find out (general) orientation of cube faces with rotated and translated camera

I have the following problem. I have a camera that is initially looking at a cube. The cube is with center at (0, 0, 0). The camera that is initially on (0, 0, 60). The camera can rotate and translate ...
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1 answer
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Speed up Reaction-Diffusion simulation calculations in Unity

I'm trying to use Unity Job system to speed up some calculation related to Reaction-Diffusion simulation. The calculations requires 2 matrixes, current and ...
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How are transformation matrices usually represented?

I know the bare minimum to do matrix multiplication and have implemented them from scratch a few times for various purposes, but every time I do, I make sure to be very clear to myself about where are ...
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How to decompose a GLSL mat4 to original RTS values within vertex shader?

I need to get the rotation differences between the model and the camera. convert the values to radians/degrees and pass it to the fragment shader. for that I need to decompose and the Model rotation ...
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What is the correct way to combine transforms together?

I have a type called transform in my game engine: ...
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How to define custom coordinate space?

I'm trying to build small UI framework. And I want it to have a coordinate space such that origin is placed in top left corner (x increases to right, y increases to down). I think for UI it should be ...
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1 answer
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Get local position of a skinned vertex

I have a formula for skinning, where a vertex is attached to 2 joints with some proportions: B = M1*A*K1 + M2*A*K1 Where: K1 and K2 are the proportion ...
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Meshes seem to get distorted when I use rotate or zoom transforms (XNA/Monogame)

Whenever I seem to create a rotation matrix or try to zoom, the meshes that I draw to the screen get stretched and distorted. I've tried to make a simple rotation matrix like this: ...
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How to solve for the angle of a axis/angle rotation that gets me closest to a specific orientation

I’m using a 3D affine transform (a 4x4 matrix of floats) to represent a combination of translations and rotations in 3D space doing a sort of 3D turtle graphics kind of thing. From this state I know ...
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Right Axis warps on 3D planet's equator

I am using JavaScript and WebGL for a game which rotates a spaceship around a 3D planet. Below is the code for rotating a sphere spaceship and sphere planet. I looked over your camera code and now it ...
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Trying to understand proper naming of transformations and coordinate systems

So far in my code I only dealt with transform matrices that I fed to OpenGL (the 4x4 float matrices), and had a class that was used to do transformations on the CPU side and generate the OpenGL ...
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Is there a way to figure out in which quad I am in fragment shader?

In my openGL project I draw a lot of quads (composed from 2 triangles) - for sake of example let's say quad 0,1,2 and 3. I process them in single pass. I do transform them with projection view matrix ...
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2d zooming function using transformation matrix

I'm trying to create a sort of "graphing calculator coordinate system" where you can zoom into a point by scrolling with the mouse wheel. I'm using javafx's transformation matrices (Affines) ...
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Rotation matrix for a model where the forward axis is not +X

I'm trying to convert a normalized unit vector, representing an entity heading, into a rotation matrix for rendering. The problem is that I'm using an (apparently) unusual forward vector for my ...
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Obj file vertex coordinates to new coordinate space

I am trying to convert the vertex positions in my obj file to a new coordinate system. I understand I need to multiply each vertex with the transformation matrix, however I am trying to figure out the ...
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Calculating view matrix from rotation, elevation and location

I have the rotation(A), elevation(B) and location(C) of a camera in a left handed 3d space. +...
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Difference between World matrix and Model matrix?

My current understanding of the Model matrix is that it is per object and stores the transformation, rotation, and scale of the object in local object space. What I'm not sure about, is that whether ...
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What are the pros and cons to using Transform{position, scale, rotation} over Matrix (3x4)?

I'm using Transform in a certain case where I want extracting/changing/preserving the components {position, scale, rotation} to be straightforward - I guess that is a benefit. But when it comes to ...
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Matrix math in cascade shadow mapping

I am implementing cascade shadow mapping algorithm and currently stuck with matrix transformations - my AABBs, when projected in light space are pointing in the direction opposite to the light: I was ...
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1 answer
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Drawing OpenGL camera frustum

I am trying to display camera frustum in my OpenGL application. I calculate the vertices of the frustum pyramid using reverse projection from screen space to world space. The camera uses perspective ...
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How do I make 2D Camera Matrix with zoom?

I trying to understand how to make a 2D Camera Matrix. The problem now is when I zoom the world shifts horizontally. The Camera need to zoom on the current Position. ...
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Scene graph with camera

I need help with a little problem in my project, in which I have a scene graph with the intented camera like this: MovementNode Camera Node Mesh Object My problem is that I have the propagation of ...
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How to rotate multi-tile structure on grid?

I need to be able to place structures in my game that span multiple tiles and can also be rotated. My idea on how to solve this would be to use 2D arrays that hold data about the structure. EXAMPLE: (...
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Need help getting an objects orientation / all my OpenGL rotations are reversed

I'm using OpenGL on Ubuntu Linux with the Eclipse IDE and the GCC compiler. I am bringing blender models into a homemade renderer/game engine. I parse a text file containing object descriptions to ...
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convert world to screen coordinates with camera position and camera angle

Heyho :) I'm trying to convert world coordinates to screen coordinates. I have available: fov, screen width, screen height, camera position, camera angle and obviously the position of the object in ...
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441 views

Calculate angular velocity from rotation matrix difference

I am working on something for a game. I need to calculate the angular velocity, however in my situation I only have access to the previous rotation matrix and the current rotation matrix (and some ...
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Invert parent transform (doesn't work for combination of rotation and scale)

My problem I'm working with Qt3D and my problem is almost exactly like this one: https://stackoverflow.com/q/60995155/3405291 Suggested solution A solution is suggested here: https://stackoverflow.com/...
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How does glm::lookAt produce a View Matrix?

Say we do this: glm::mat4 View = glm::lookAt(glm::vec3(4,3,-3), glm::vec3(0,0,0),glm::vec3(0,1,0)); And after printing to the console with glm tostring (column ...
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Convert Global Space 3D Location to Local object space?

I'm trying to find a formula that could convert my 3D global coordinates into local object space. Here are the inputs I have ...
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Cylindrical billboarding around an arbitrary axis in geometry shader

I found an answer on this site relating to this question already, but it doesn't seem applicable in the context of my project. Basically I'd like to create a method which fits this signature: ...
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How to decompose a 4x4 TRS transformation matrix with negative scale?

As the title says I need to decompose 4x4 TRS transformation matrices and extract the proper scale vectors and the proper rotation vectors (or rotation quaternions). I know how to extract those ...
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Shifting the world origin and scaling all points?

Imagine you have a simulation in very large coordinates, and to render it out you need to scale it down (say, solar system -> fitting inside a few thousand units). This is controlled by a float ...

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