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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85 views

Inverse transformation matrix for checking whether a point is inside a rect

I'm trying to determine which nodes in my scene graph contain a given point in global coordinate space, using the inverse of the node's global transformation matrices. Here's a simplified version of ...
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From look-at vectors to a quaternion

So, I have code to create a quaternion from a matrix (using the 3x3 rotational part.) And I have code to construct a transformation matrix from a lookat + up vector pair. To go from lookat+up to ...
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Finding islands from array

Say I have an two dimensional array with values 0 or 1. How would I construct an algorithm (preferably in C#) to work out which ones are separated or islands. The algorithm would transform the left 2d ...
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Matrix for transforming a square to a quadrilateral

I have a square of points {<0, 0, 0>, <6, 0, 0>, <6,0, 6>, <0,0,6>} (The square is placed at the origin in the xz plane in opengl). Want to apply a transformation/s on the square and make ...
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Z rotation matrix inverting object

I'm currently creating a 3d game where I need to rotate shapes. To do se, I created a rotation matrix for each axis, X, Y and Z. X and Y are giving me expected results, but not Z who kind of "inverts ...
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3d isometric projection matrix?

I have 3d vectors that I want to project as 2d vectors to draw my shapes. I got a 3d vector cameraPosition, a 3d vector cameraDirection, a float renderDistance. I need to create an orthogonal / ...
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Orientation is off when nearing 90 degrees rotation

Context: I am using Vive Trackers to track the head of a user. It is not a Vive headset and I am restricted to the TrackingUniverseRawAndUncalibrated, which only guarantees that the Y axis will be UP. ...
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247 views

Finding translation component of a 4x4 matrix inverse

I have 4x4 matrix (A) (maya softw): ...
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1answer
323 views

How to set ortho projection / model view matrix without a camera?

I'm trying to create the correct projection and model view matrix for rendering without a camera. _orthoCamera is a camera I set up in the scene view. Using the <...
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1answer
337 views

Normal Matrix in plain English

I'm into shader language with Webgl and GLSL. I've seen some tutorial about normal matrix and I don't really understand it. I mean, I think I'm ok with the math such as: ...
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Simplify Matrix math code- Sun billboarding

If was trying to set the correct position of my sun billboard in my 3d game. I tried long until it worked correctly, but I wonder why this code must be so complicated: ...
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382 views

What exactly does XMMatrixPerspective{L,R}H do?

There are generally three functions to create a perspective matrix in DirectXMath, XMMatrixPerspective{L,R}H, ...
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2answers
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most compact way to represent dice face translations rolling in cardinal directions

I'm making a 2-D dice rolling game in BASIC (think mechanics similar to Devil Dice on the Playstation, but top-down 2D graphics). I'm trying to accurately represent the transitions of a die when ...
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1answer
106 views

Unity Graphics.DrawMesh lags behind rotation?

I have a setup in unity using Graphics.DrawMesh() to draw a mesh on my players camera location in the update loop, ...
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135 views

btRigidBody world transform and scale issue

When I create a collision shape for rigid body (in this case box) I use vertices positions and scale from the opengl matrix, the code looks this way: ...
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99 views

Convert bones by bone matrix

I have a 3d-models from old game. They have the following structure: ...
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1answer
133 views

Combine rotation XZ (horizontal) with YZ (vertical). Math formula

I'm trying to make a rotation vertically and horizontally around a point at the same time but I'm not able to combine both. I have this formula for the horizontal rotation: ...
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Blender - Exporting and Replicating Bone Animation

I'm having trouble replicating Blender bone animation in my game. Bones that have a vertical rest position (Euler(PI / 2, 0, 0)) are animated correctly (e.g. head, neck, torso, legs, shins), however ...
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2answers
353 views

How to access coordinates of objects in bullet physics (libGDX)?

I need to access the x, y and z coordinates of a bullet physics object. I'm assuming this is done via the transform matrix, but I have no idea which values mean what. There doesn't seem to be any ...
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1answer
80 views

Determine view-matrix with camera placed in a scene graph

My scene is organized with a simple scene graph where the child multiplies its transformation with the one of the parent. For normal objects, likes meshes, this works as expected, but I also want to ...
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Does it make sense for a view matrix to have a scale?

When building a view matrix from an SRT matrix multiply, examples (here and here) only ever compose it with a R and T. Does it make sense to have the S component be anything other than the identity? ...
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1answer
23 views

Display object at different position

Id' like to create impression of shaking holographic image of NPC in Unity 2018, but moving it with transform will cause unnecesary transform-rigidbody syncing, and using Rigodbody.position isn't an ...
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1answer
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How do Axis-Aligned Bounding Boxes update with rotations?

I have a bounding box class with a min (x,y,z) and max point (x,y,z). The object that is being rotated has a rotation matrix (3x3 matrix), but I don't know how to update the bounding box with ...
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3answers
619 views

Rotation of a matrix with unequal rows and columns

I have this simple matrix class which has a char** array for storing the data. The data array gets initialized like this: ...
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1answer
579 views

OpenGL vector rotation matrix to a given point

I have a sphere with a radius of .5 The sphere is centred at 0,0,0 I am now trying to place items around my sphere based on a given x,y,z on the surface of the sphere. My items have been draw/...
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1answer
106 views

Sun model matrix

I'm playing with sun implementation in my engine and I correctly built model matrix using below order of matrix operations: Translate to camera position. Calculate x and y axis of rotation matrix ...
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1answer
301 views

Why does a translation matrix need extra row?

Following recommendation of this answer I've recently read the series of articles of Wolfire about linear algebra. I'm somewhat familiar with matrices and I came to a conclusion that vector and a ...
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anything wrong with a spherical camera view matrix?

Is there anything inherently wrong, if you derive your view matrix from 2 spherical coordinates (say, phi and theta) on the unit sphere? The z-axis vector would be at, say (phi, theta), the y-axis at (...
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OpenAL listener position for isometric camera

I have an isometric camera for an RTS that looks like this: Basically, I don't know how to set the listener's position in OpenAL because I represent the camera's position with only two coordinates. ...
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1answer
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How do i rotate my view on its own center

PROBLEM I am trying to translate and rotate my view, the translation works fine but when rotating the rotation is happening on the center of the world(0,0,0) instead of the view position. EXAMPLE ...
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1answer
34 views

How can I have more values in array on X axis than Y axis in my tilemap?

Following my old question Array of map data renders the map the opposite way after I got the answer to it and fixed my problem, I got another problem that occurs. If my ...
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2answers
719 views

Is clipping done before or after projection?

Is clipping applied after projection or before? How can it be applied after projection when a vertex is behind the camera and projected therefore mirrored? At this time I clip the triangle before ...
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1answer
45 views

Optimizing expensive calculation for calculating touch of side of cube

I have this code: ...
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2answers
69 views

How to keep an object in a certain part of the camera view?

I have a 3d camera that is viewing a character that is moving. As the character is moving i want the camera to adjust itself so as to keep the character in the left third of the camera view. I ...
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1answer
72 views

Texture does not fit the screen

Hi guys I am really new in OpenGL-ES and I am developing a simple android application with NDK, and I just want to ask why the image is not fit after I set the width and height of it. this is my <...
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1answer
418 views

Camera movement issue with pitch and yaw angles

I'm trying to implement a simple first person camera using pitch and yaw angles (no quaternions, I want a simple camera for debugging purposes). An Input class processes mouse input and translate the ...
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1answer
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Camera rotation is weird when it's a child of another object

I implemented scene graph hierarchy into my 3D game engine, and there seems to be a problem with the camera's rotation when it is a child of another object. It only happens with the camera, not any ...
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1answer
2k views

Why do these DirectXMath functions seem like they return column-major matrics?

I know these questions have been asked a million times in various formats, but I'm getting weirdly skeptical about some of the row-major vs. column-major claims about the DirectXMath library. If I ...
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1answer
160 views

Change center point and size with the help of the Matrix in Unity

Let us suppose I have an array of Vector3, it contains vertices. Now I want to scale the vertices and/or change the center point of the texture (move texture ...
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1answer
2k views

What is FRotationMatrix in Unreal engine 4?

I am working on FPS shooter example in Unreal engine 4 documentation. One of the lines for forward movement of pawn is ...
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1answer
358 views

Get enemy/chaser object to face player object - OpenGL

My chaser object will not face the player object. It simply keeps spinning around and won't face the player. ...
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2answers
205 views

TRS Matrix between 2 points

I have got 2 Points in 3D Space whose TRS Matrix' from 0.0 to there current place is known. Now I want to change the Matrix of the left point so that the matrix of the right point combined with the ...
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1answer
106 views

Camera rotation deforms objects

I'm working on a ray-tracer in C++ with an adjustable camera for a university assignment. I'm entirely new with graphics and I'm struggling with one thing. I have a matrix as a mat4 object (4x4 ...
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1answer
83 views

Split a grid into shapes that can be moved back from 4 directions

Basically I have 4 grids Left, Right, Top, Bottom. Player can choose each of them and move all the blocks on that grid to the Middle grid to fulfill it, like tetris from 4 directions: ...
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1answer
71 views

LibGDX trying to create a matrix of circles

I am trying to create a circular stage like so: But I can only make a square:
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452 views

Setting relative anchor point via matrix

The page at https://webglfundamentals.org/webgl/lessons/webgl-2d-matrices.html provides an example for rotating around the center of the image: ...
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1answer
7k views

lookAt with orthographic camera (gl-matrix)

Technically this is a webgl question though I think it's generic enough to get some opengl, erm, perspective on it too... If I setup an orthographic camera (perspective matrix) like this: ...
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1answer
9k views

How to mirror/reflect/flip a 4D transformation matrix

I am importing my animation keyframe joint data from Blender to my game engine. The joint data is a set of 4D matrices. Things are looking good except a remaining issue where the animation is facing ...
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1answer
2k views

How to Convert a Z Up Matrix to a Y Up Matrix?

My 3D program exports my vertex data and instancing matrixes in Z+ up format. I want to store them in my own data format as Y+ up. If given a Matrix4 describing a position with Z+ being up. How can ...
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1answer
850 views

Matrix multiplication order for multiple model transformations

I have a problem in terms of what frame of reference, I should construct, scaling (S), rotation (R) and translation (T) for a model matrix (in that order). Let us assume the use of glm (or glsl), i.e. ...

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