# Tagged Questions

A mathematical concept that can be used to express position, direction or velocity and which can simplify or outright trivialise spatial problems.

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### What is a direction vector and why should it be normalized?

I've been trying to get the hang of vectors and I read Wolfire's blog about linear algebra and I seem to understand most stuff except when it comes to storing a direction as a vector and using it by ...
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### Vector Math question

Suppose I have two game object located at two Vector3s v1 and v2, respectively. If I wanted to locate a position between v1 ad v2, but 3 units away from v2, how would I manage that in terms of ...
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### Why not use vectors to represent orientation?

From what I've read, people mostly use either quaternions or 3x3 matrices to represent 3D orientations, while plain vectors are used for angular velocity/momentum. Since we can use vectors to ...
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### Moving in a diamond - enemy gets stuck

I have an enemy that I would like to move as follows: Start at (0, 200, 0) Move to (200, 0, 0) Move to (0, -200, 0) Move to (-200, 0, 0) Move to start point, repeat as long as it remains active. ...
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### How can I calculate a vertex normal for a hard edge?

Here is a picture of a lovely polygon: Circled is a vertex, and numbered are its adjacent faces. I have calculated the normals of those faces as such (not yet normalized, 0-indexed): Vertex 1 ...
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### Calculate vector in local space

I have a vector (8,5). It's origin is at (10,9) I can calculate a perpendicular like so: MyPerpendicularVector.x = -MyVector.y MyPerpendicularVector.y = MyVector.x Given that I now know these two ...
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### How do I find rotation in 3D based on a vector/normal?

I've been playing with Blender and Python, doing basic things like accessing vertices/normals,etc. I can get the normal of each face of a mesh. I was wondering, how can I get the rotation of a face ...
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### Should we go for our Vector2Int/Vector3Int implementation or just use built-in float based vectors?

So in one of our projects we're using Vector2/Vector3's a lot but we do only use integer/byte values mostly. So up to the point we've implemented our Vector2Int, Vector3Int, Vector2Byte and so ...
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### Getting an angle in degrees from north

This may have been asked already, but I was unable to find it, because I don't really know what I'm looking for. I drew a picture: I need theta. I've seen various solutions using Vector.Dot, and ...
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### Raycasting tutorial / vector math question

I'm checking out this nice raycasting tutorial at http://lodev.org/cgtutor/raycasting.html and have a probably very simple math question. In the DDA algorithm I'm having trouble understanding the ...
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### Trouble with speed and vectors

I'm working on adding bullets to my game. Right now I can shoot bullets in the direction that I would like from a ship by getting the ship's angle: int speed = 5; int dx = -(cos(degreesToRadians(...
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### How to find the entity I'm looking at?

I am currently making a mod for Minecraft but I have come to a stop because I am lacking in some knowledge. I need to get data for the entity I am looking at, which I believe requires the use vectors, ...
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### What is a good way to determine if a vector is between two other vectors in 2D?

I could operate with the angles, but I do not have the angles calculated yet (and would like to avoid having to do that). It would be possible to calculate and cache the local-coordinate-frame angles, ...
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### Rotating plane to be parallel to given normal via change of basis

I have two planes and their respective normals. I would like to rotate the second plane, planeB, so that it is parallel to the first, planeA. To do this, I am using a change of basis to rotate each ...
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### Why isn't this physics code scaling velocities separately?

I'm working my way through this book and I'm trying to work this code out: var squaredVelocity = this.velocity.x*this.velocity.x + this.velocity.z*this.velocity.z; if (...
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### What are the properties of “position, velocity, acceleration, rotation” collectively named?

They say naming things is one of the hardest problems in computer programming. They were right. Given the pseudocode below, what is a more appropriate name for this collection of properties? "Course",...
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### Rotate vector by matrix?

If I have a Vector, say (1,1), how can I rotate it around the origin (0,0)? I'm working in XNA if that helps.
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### How can I find the perpendicular to a 2D vector?

I'm making a top down game where the player moves forwards towards the position of the mouse cursor. As part of the player's movement code, I need to determine a vector that is perpendicular to the ...
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### Tetris - Rotations using Linear Algebra (Rotation Matrices)

I'm making Tetris in Java and am at the point of rotations... Originally I was hardcoding each rotation: if (direction.equals("right")) { if (shape.equals("Bar")) { if (...
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### Given an angle for an arrow, how do I find its X and Y velocities?

I want to fire an arrow toward the mouse location. X0 = the players X location X1 = the mouse X location Y0 = the players Y location Y1 = the mouse Y location I want to make a method which takes ...
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### Does vector transformation order matter?

Theoretical question - imagine a car object. There are two (or more) 'forces' acting on this car, these forces will affect where the car will steer. But the forces are calculated using car's location ...
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### How to bounce a 2d point particle off of a circular edge

In a prototype I'm building, a particle can spawn anywhere within a larger, confining circle. Important to note is that the particle will not spawn in the origin of the larger circle, but anywhere ...
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### Why game engines usually don't offer a vector3.rotate method? [closed]

Game engines like Three.js, Ogre3d and Unity3d often don't provide a default rotate method on their vector class. You usually have to do something like: rotated = vector.applyQuaternion( new ...
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### How do I find a point given an angle and distance to it?

I'm working on a school project creating a tank team in the programming game Robocode. (It's a tank battle game with self-programmed bots, in Java). I'm programming a scout bot that scans, finds ...
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### Most effective way to manage a gamestate system that is easy to use?

I just started working on my game, mostly the game management. I plan and using game-states to make the menu's and other stuff easier. My main idea for implementing the game-states is creating a game ...
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### How do I determine the position of one vector relative to another?

I'm making a game for Kinect in Unity which tracks hand movements. I have the player's root position and the position of their fist stored as 3-dimensional vectors (Vector3 in Unity), but they're both ...
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### How to Calculate the Contact Point between Ray and Plane

Is there any quick way to find the intersection point between Plane and Ray?
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### Movement with Vector Math

After reading This SO post on Vectors, I'm still pretty confused on how to use vectors to move my entities at any angle. The SO post assumes only 90 degree angles: if up pressed: direction = ...
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### Calculating normal vector on a 2d pixelated map

I want to know an efficient way to get the normal of the surface of a 2d map. suppose an object hit the map, i want the object to bounce accordingly. The problem is, the "bounding box" of said object ...
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### Points on lines where the two lines are the closest together

I'm trying to find the points on two lines where the two lines are the closest. I've implemented the following method (Points and Vectors are as you'd expect, and a Line consists of a Point on the ...
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### Implementing vector based movement in a 2d environment

Good evening. I apologize if the title is a bit vague, I really could not come up with anything better. I am currently reading a book called the nature of code and as a side project, I am working on ...
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### Drawing a texture line between two vectors in XNA WP7

I want to create a simple graph maker in WP7. The goal is to draw a texture line between two vectors what the user defines with touch. I already made the rotation, and it is working, but not ...
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### Limit rotation heading by cone/angle

What is a fast way of limiting the heading vector to a certain angle so that it turns in greater distance relative to the limit. A smaller cone/angle should make the object take a far bigger curve to ...
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### Implementing proportional navigation in 3D

Good afternoon guys, a = N * λ' * V is the formula for the commanded acceleration required to hit the target, where N is the proportionality constant, λ' is the change in line of sight and V is ...
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### Find your value between four values in a grid based on distance, Unity

Please note: Originally posted in stack overflow, redirected due to nature of problem. I am making a procedural mesh game. I am trying to calculate the temperature for the player's current chunk by ...
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### Normalization of Vectors: Return a copy of the result or alter the object itself?

When calculating the normal of a vector, which is considered canon: Returning a copy: Vector2D Vector2D::Normalize() const { double a1 = GetX(); double a2 = GetY(); double a3 = GetZ(); ...
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### Is it better to track rotation with a vector or a float?

In XNA, you can see that to draw a rotated sprite with SpriteBatch, you'll need a float describing the angle in radians. I'm used to making games in OpenGL. I just want a rapid prototyping ...
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### How to get the closest “visible” object from my “player”?

I'm using Unity 3d and i have to accomplish the following task: get the closest "visible" object to my player in forward direction. It is a sort of radar. I don't know where to start. Any advice ...
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### How to find point on a circle that's opposite another point?

How do I find the coordinate of point and angle value on circle sprite which placed on opposite side of sprite from a touch point and the center point of the sprite? I know A position, B position and ...
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### How to implement object velocity as a vector

I'm working on a Breakout game, and want to change the ball's movement code from how I currently do it, to something based on vectors (as I feel learning and implementing movement based on vectors ...
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### 2 component unit vector

Is it possible to store a 3d unit length vector with only 2 components, for example as coordinates on a unit sphere? It seems possible but I have never seen anyone do this. Would this be at all ...
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### How do I interpret the dot product of non-normalized vectors?

I know that if you take the dot-product of two normalized vectors, you get the cosine of the angle between them. But if I take the dot-product of two non-normalized vectors (or one normalized, one ...
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### How to calculate left/right oriented angle between two 2D vectors? [duplicate]

I would like to calculate angle between two 2D vectors. Here's a picture of what I'm trying to achieve: I have an obstacle line segment AB and incoming moving PC. If I'm coming from one side C¹D¹ ...
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### How can I implement a directional melee attack?

I am attempting to make a top down game similar to the SNES Zelda games, in Unity 4.3, in 2D. When my character swings their sword, every enemy within a radius takes damage. I want to make sure that ...
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### What kind of projection is ScreenX=X/Z, ScreenY=Y/Z?

I have an existing class which transforms 3D vectors and projects them on a 2D plane (Camera). The code is all written in C without help from an external library. To project a single vector (X,Y,Z) ...
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### How do you transform a vector to use another objects orientation?

I want to take a vector that is using world coordinates and position it using the orientation of an object. So, if the direction of the object is the z-axis, and the vector is (0,0,1), then the ...
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### Line triangle intersection - last bits

I'm doing line-triangle intersection. I have found the intersection point (vector) on the plane. All I need to do now is work out whether the point is inside the triangle it collided with (not the ...
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### Intersection of a Line and a Rectangle

I have to calculate the intersection of a line segment (represented by 2 points) with a rectangle. For example: Axis aligned rectangle corners: (0, 0) (100, 100) Point 1: (50, 50) Point 2: (50, ...