# Questions tagged [linear-algebra]

Linear algebra is the branch of mathematics concerning vector spaces and linear mappings between such spaces. The tag is generally used for questions regarding calculations over vectors.

29 questions with no upvoted or accepted answers
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### What is the most efficient way to determine collision path

I am trying to create a game in which I need to know if two objects will collide in the future, and when. I have both object's position, radius (they are circles) and velocity. A specific example of ...
34 views

### Find point along x axis where yz plane flips to back facing after perspective projection. Have a solution but don't know why it works

I am trying to find the point along the x axis where a plane with normal pointing along the x axis would flip to back facing after perspective projection. Essentially the red line in this image. My ...
54 views

### How to vary the initial velocity of a jump based on hold time?

What I want to do is, the longer player holds the screen, the longer distance the object will jump when they release the hold. Here is my code: ...
82 views

### Applying multiple forces on a particle

If I have a particle, say in a polar coordinate grid, and I want to apply multiple vectors to it, how can I calculate where it's final position will be given those vectors? Ex. Imagine there's a ...
249 views

### How do I create the formula for calculate the damage of a skill

I'm trying to calculate the output damage of a skill. The skill can go up from level 1 to 100, it can scale with own levels and the attack of the character. Here some parameters Edit: I need a ...
130 views

### convert 2d pt into non-affine coordinate system

Say I have a coordinate system that goes from (0,0) to (1,1). We'll call this screen_space. ...
568 views

### Closest distance from 3D point to vector line

First let's have a look at my little drawing: I have an origin point p1 defined by x, y and z co-ordinates, and a vector v given by x, y and z magnitude. I also have an arbitrary point, p2, given ...
1k views

### How to rotate a line in 3d space?

I am trying to figure out direction vectors of the arrowheads of an arrow. Basically I'm given a normalized direction vector ...
60 views

### Calculating child world translation, rotation and scale

I'd like to know if it's possible to calculate a child's world translation, rotation and scale individually. I'm used to seeing devs resorting to matrix multiplication and then decomposition, like so: ...
40 views

### How do I create surfing?

I want to know how I can lerp from my current position, to another position, while hugging the terrain. Imagine I'm doing something like surfing, or skateboarding, where I need to follow the rail......
73 views

### Writing a sphere-sphere intersection function

I am writing a function where I have two 3d points with coordinates {x, y, z} both with a line segment of a given length. I am trying to find a common endpoint between the two line segments closest to ...
13 views

### Line Clipping and warped Picture

So hello to all of you, I wrote some pseudo 3d Code in QB64 (just for testing) and I managed to get the program running. So my problem is, that i get some disorted pictures when it renders the walls. ...
27 views

### How to check if a particular vector is pointing at X-Y plane or Y-Z plane

As you can observe from the diagram, Vector A is pointing at the Y-Z plane and Vector B is pointing at X-Y plane. Is this possible to find? Am I missing some logic or concept? EDIT: Suppose, Vector B ...
31 views

### Rotating a cube with arrow keys

I have a list of rotations (on a cube in 3d space with the y-Axis pointing upwards, x-Axis pointing righthand and z-Axis pointing towards you) for example +90 deg around x-Axis followed by +90 deg ...
19 views

### Scaling transforms by time, Eigen Decomposition of Affine Transforms

I posted this question in mathematics, but that sight gets flooded with homework problems... 8 views total, most of them me. Plus, I think this question is more geared to game development anyway. I am ...
23 views

### Is there a way to invert the scaling of the axis and keep the orthogonality?

Recently I ask question and since then been decide to find solution by dividing scale matrix to two part GlobalScale and ...
64 views

### How to get correct axis for scaling from transformed space?

I have scaled and non-scaled representation of model so that I don't destroy verticis information if model will be scaled to plane, for example. Now I trying implement scaling on model elements (face, ...
199 views

### Understanding use of dot product in speed boost pad

I am trying to understand the dot product. I have found a website that gives you intuition about this topic and one of the examples involves a speed boost pad: Imagine the red vector is your speed (x ...
103 views

### Rotation of a 3D ball on a plane

This used to be on the physics stack exchange but I was told to put it here: I'm making a game (with physics) and I have a 3D ball rolling down a flat plane. It moves perfectly fine, but the rotation ...
103 views

### OBB Frustrum Culling in Clip Space

I've been trying for a while to implement a frustum culling method using a per-computed AABB in object space and transforming it's corners into clip space. ...
60 views

### What is a good algorithm for generating a linear regression of positions in 3D space? (for getting the direction of a thrown object in VR)

I'm trying to get throwing to feel right in my VR game. I don't plan on actually using physics to do this; my idea is to accurately determine the lateral direction of the throw, then move the object ...
191 views

### Getting the Closet Points between Polygons with the GJK Algorithm

I am trying to implement the GJK algorithm by following this lecture. For the most part, it is working, but sometimes 1 of the 2 closest points is incorrect. Here are two examples: EXAMPLE 1: The ...
69 views

### Leading a target with edge casting

I am trying to write a movement prediction code. I have found the quadratic method with these topics: : How to calculate shot angle and velocity to hit a moving target? : http://...
124 views

### Calculate smooth transition between local space angles

I'm trying to calculate direction of moving character (to rotate it's animation). I have something like this: Character can have 4 cardinal directions. The rotation is calculated from the current ...
714 views

### Dot product not working as expected

Recently I am learning dot product, While below code works from Unity's documentation, http://docs.unity3d.com/ScriptReference/Vector3.Dot.html ...
136 views

### Project 2d click/touch onto 3d plane

I have a 3d scene that contains an infinite plane that is NOT parallel to the camera (so every screen coordinate corresponds to a point on this plane- in other words, there are no possible invalid ...
185 views

### XNA Rotate Vector2 around Origin

I have a Rectangle and a Vector2 position, my sprite is being drawn at this position. The rectangle is meant to be a collision system with the cursor, when I rotate my sprite around the origin and ...