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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30 views

Issues with rigging and converting from local space to world space

I'm currently designing the rigging system of my game engine. Currently, all bones and joints store a local position and rotation matrix. These are multiplied (rotation * position) to create a local ...
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152 views

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

I'm trying to create a camera using matrix transforms, the gist is as follows: ...
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Rotate & Translate a MatrixTRS

Hello I have a question about translation & rotation of a MatrixTRS... So basicly I have a given MatrixTRS A in space, define by a positionA, rotationA and scaleA. (DISCLAIMER: I am using Unity, ...
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Random 100x100 map using all levels from 1 to 100

I'm developing a game where players walk though a 100x100 grid of different rooms. Each room has a level associated with it starting from lvl 1 to lvl 100. The map is divided into 10x10 areas and in ...
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41 views

Rotation matrix to look at point p

Assume a left-handed coordinate system where x is right, y is up, and z is into the screen. You have a unit vector pointing up along the y-axis. What's the rotation matrix for pointing the unit vector ...
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What is an efficient way to get a look-at direction from either a quaternion or a transformation matrix?

So, I have an object in my custom engine (C++), with a column-major transform in world space. I'm using a package that takes a look-at direction as an input. What's the most efficient way to get a ...
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How can I transform a 3D triangle to be coplanar with another congruent triangle? - How can I superimpose two congruent triangles?

I need to transform an equilateral triangle that is lying flat on the xz plane, to become coplanar with another congruent equilateral triangle. I am developing a simple low-poly space exploration game,...
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OpenGL Drawing triangles at given world coordinates in modern opengl

It's my first time I am asking a question here so I apologize in advance for any mistake. In the past two days, I decided to work on a 2D lighting system for my game and I came across a youtube ...
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When using transformation matrices, how does one convert orientation and scaling from a global frame of reference into a local one?

Note: I'm certain I cannot be the first to answer this question. Unfortunately, the answers I need are buried under an avalanche of posts asking how to move coordinates between frames of reference, ...
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Rotate Object in world space - Raytracing

I’m programming a C raytracing project. I’ve been wanting to implement object rotations (square, cylinder) for several days but I can’t do it. For each object I have its position (x, y, z) in the ...
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Rotate meshes with different pivots, equality

If I have multiple equal meshes but with different pivots and I make a rotation on the first, is there a way to replicate this rotation to all meshes using a rotation Matrix? For example, if I have a ...
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Recognize L-Shape in a 4x4 Matrix

I'm trying to make a board game, there the player has to press four buttons to make the L. It can be mirrored or rotated, it just has to be an L. But if the player press four buttons and make another ...
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Match-3 should pieces store their location in the matrix?

I'm making a match-3 game. I have a TileManager script which stores all the tiles in a matrix, it's a singleton and it handles tile swapping and basicly everything regarding the management of tiles. I ...
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How do you convert an object to camera view with a matrix

I've been stuck with this math problem for quite some time. I'm trying to convert an object to viewport coordinates, similar to gluLookAt. I tried putting the ...
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Intersection of ray and non-axis-aligned box

I need to compute the intersection of a ray with a non-axis aligned box. Currently, I transform the ray into the local space of the box, do classic ray-AABB intersection and transform the intersection ...
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What is the signifigance of the Dot Product in World to Local Transformations?

Looking for help understanding why this World to Local Space function works. I'm working my way through Buckland's Programming Game AI By Example The following function is used in the book to convert ...
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244 views

Should 3D transformations be represented by a 4x4 matrix or a 3x4 matrix?

Since 3D transformations are represented by 4x4 homogeneous matrices we know that their last row is always (0,0,0,1), and as such the behavior of this final row is implied so long as we know whether ...
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Projecting Coordinates from one Space into another, but with “twisting”

i'm trying to generate a decal mesh kinda like this: http://blog.wolfire.com/2009/06/how-to-project-decals/ but instead of projecting the decal with a box, i need to project it with a sort of ...
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Can't get world position from reverse Z buffer

I'm using this solution to render using a reversed Z buffer. This looks fine and completely fixes all my z-fighting, but it breaks what I use in shader to derive the world position from the depth for ...
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Why does the Modelview Matrix in OpenGL not have accurately signed vector values for look vectors?

When I do a GluLookAt(0.0, 500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0) so that I'm 500 units up on the positive Y axis looking down at the origin with the top vector of the camera pointing toward the ...
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1answer
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Scaling a rotated child with parent-child transforms

In unity, if you parent something to another object, then give the child some rotation, and scale the parent, the scale applies to some arbitrary axis to the child, here's some pictures to demonstrate:...
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How to apply a color transform to textures when using pre-multiplied alpha?

I'm trying to apply a color map to my textures. The map is a 4x4 matrix that adjusts the contribution of each RGBA channel returned from the fragment shader. My texture needs to use pre-multiplied ...
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My triangle disappears when multiplaying by my perspective projection matrix

Whenever I multiply my transformation matrix, which is passed to the shader via constant buffer, my triangle disappears. Here is the code for the passed matrix: ...
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1answer
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matrices and nesting hierarchy with game objects

Let's say we have some game objects and they are nested to form a tree: - A - B - C - D If each of those have a matrix for the scale, rotation and ...
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1answer
31 views

Broken model matrix builder

I'm trying to setup basic render pipeline in Vulkan and am currently setting up the perspective, view and model matrices. The line that calculates the position in the vertex shader is this: ...
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How to convert screen to world coordinates while using gluLookAt / gluPerspective or similar matrix transforms?

I am just starting an adventure in looking under the hood of graphics for a game project I've been working on for a while, and I could use some guidance. I am using Python/Kivy (though that is not ...
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How to fix roll in FPS camera when looking sideways [duplicate]

I am trying to calculate the rotation for an FPS camera. My closest attempt was to create a some Euler angles(from input) and multiply that with the view matrix, this works, but only if I am looking ...
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1answer
421 views

THREE.JS - How to know the shortest rotation direction an object must do to look at other?

I am trying to understand a way in THREE.JS (and the mathematical foundation) to get the direction an object should rotate to lookAt other but without actually rotate it. I've tried to use ...
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How do physics bones relate to animation bones?

Skinned animations use a tree of bones where the child bone (say a finger) is the weighted sum of the rotations of all it's parent bones. Physics bones are defined as a rotation matrix of a primitive (...
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293 views

How can I skew a SpriteRenderer in an animation to grow a side and decrease the opposite side by the same amount?

I am interested in the maths and maybe the shader code. I am almost sure that this would be a great starting point but I do not have any knowledge about shaders and the language they are written in. ...
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1answer
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After rotated by Z-axis, X/Y axis still rotating just like z is 0

I'm making aerial vehicle controller, which can rotate 3 axis: X(Pitch), Y(Yaw), Z(Roll). Rotating x(pitch) and y(yaw) axis works fine, however after I rotated z(Roll) axis, x/y rotation gave me ...
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Should calculations be done on the CPU or GPU?

I'm currently learning OpenGL and it's become obvious that I can do most calculations on the CPU or the GPU. For example, I can do something like lightColor * objectColor on the CPU, then send it to ...
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1answer
95 views

What are the “axes of a matrix” exactly?

I am currently learning about game engines, and for the engine math, there are functions called GetXAxis, GetYAxis, and GetZAxis that returned the X, Y and Z axes for a matrix. These functions return ...
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How to calculate rotations for an object with scaling transformations?

I am working on implementing scaling transformations into a game engine (C++), which previously assumed only translations and rotations. Visually, the scaling works, but a lot of the game logic ...
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1answer
122 views

What should the Z coordinate be after transformed by the projection matrix?

I'm working on an OpenGL 1.x implementation for the Sega Dreamcast. Because the Dreamcast didn't have any hardware T&L the entire vertex transformation pipeline has to be done in software. What ...
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GLSL: gl_ModelViewMatrixTranspose vs. gl_ModelViewMatrix

What is the difference between doing these two operations? Don't the first transform the vector from model space to view space? Then what does the second operation do? gl_ModelViewMatrix * vec4(...
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Which is a better way for moving 3d objects in OpenGL?

I'm learning OpenGL, and I'm a bit confused. I've just learned about projection and modelview matrices which can be used for moving things. This is the first way, which is convenient if I want to move ...
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128 views

How to rotate a point around a pivot by changing the axis

I've been stuck on this forever now because I don't understand math in the slightest and when people talk about matrices they just give the table and don't explain how to actually go through each step....
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1answer
67 views

Rotate coplanar 3D points to XY

I have a set of 3D points. All these points are on the same plane. I have the normal of the plane. Now I need to rotate them in such a way that the Z value of all these points become zero. (that is, ...
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44 views

Translate operation is rotating?

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Objects World Matrix Issue in Direct3D11

I have an issue with the transform matrix of my cube. When I change its position (world matrix) and rotate the camera, it is getting deformed. Here's my shader update code: ...
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1answer
76 views

rotation matrix problems - opengl and own types

In an effort to learn things deeper I'm writing my own mathematics for the first time instead of using libraries. As far as I can tell my matrix multiplication is correct, and translation and scaling ...
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How to program 3D translate widget like in blender?

Im struggling to achieve the translation widget in my own render engine. Funny enough I thought that widgets are easy, but boy was I wrong... What I want to implement: Where I am having problems: ...
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1answer
81 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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31 views

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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242 views

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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1answer
44 views

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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