# Tagged Questions

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

668 views

### How does this circle collision detection math work?

I'm going through the wildbunny blog to learn about collision detection. I'm confused about how the vectors he's talking about come into play. Here's the part that confuses me: p = ||A-B|| – (r1+...
590 views

### Calculating projectile velocity from moving object

I'm working on a top down space shooter and am having trouble with calculating/understanding the physics for projectiles launched from the space ship. The ships have a velocity vector and a turret ...
279 views

### When to use an Array vs When to use a Vector, when dealing with GameObjects?

I understand that from other answers, Arrays and Vectors are the best choices. Many on SE claim that Linked Lists and Maps are bad for video game programming. I understand that for the most part, I ...
693 views

### Asteroids Movement

I have been making an asteroids clone, in C#. However, the ship's movement is... not quite right. My plan is this: there is a speed, and two directions, namely the direction the ship is facing (...
74 views

### Java Distance between two Vector positions never 0

I have a Player moving, but when the player reaching the destination it should stop. But problem is that distance never return 0. It starts printing this: 0.9672514210000003 End by this and then ...
90 views

### Malformed/Pixelated Vertex Normals

I am trying to generate vertex normals for a given triangles/vertices list with the following code: **BASE METHOD:** private void CalculateNormals() { for (Int32 i = 0; i < m_Meshes.Count; ++...
354 views

### Estimate the time it takes for an object to travel from point A to point B

I have an object with vec2 position, velocity, and destination with 2 variables maxspeed and acceleration. In each step, its position is calculated as follows: vec2 desiredVel = destination - ...
347 views

### matrix to rotate a vector to a known arbitrary axis

Let's say I have a vector V (v.x,v.y,v.z) which is normalized and points somewhere in 3d space. And that I have another vector Z of (0,0,1). Knowing only these two things I'm looking for a ...
210 views

### Does a 2D Vector or 2x2 Matrix play any role in 2D Transformations?

I'm having trouble trying to figure out if a vec2 or mat2 class are used at all in transformations for 2D rendering. Vec2, apart from representing UVs, AFAIK, is relatively pointless in regards to ...
3k views

### Libgdx: Am I abusing Vector2? Is there a better way to do my position updates and rendering?

I'm simulating hair in a game. Currently I have a HairField object, which has a position defined by a Vector2. Each HairField has multiple Hair objects in a list, each with a position defined by a ...
1k views

### Rotate triangle so that its tip points in the direction of the point on the screen that we last touched

OpenGL ES - Android. Hello all, I am unable to rotate the triangle accordingly in such a way that its tip always points to my finger. What i did : Constructed a triangle in by GL.GL_TRIANGLES. Added ...
1k views

### Calculating angle between two vectors to steer towards a target

I have been trying to implement a path following steering behaviour for AI in a 2D racing game. I have two vectors: futurePosition represents the predicted future position given the car's current ...
101 views

### Get perpendicular vector from another vector

I should clarify that I understand there is an infinite amount of 'perpendicular' vectors in 3D space. I am creating an electricity effect, and to do this the ability to have any number of ...
86 views

### How to make an enemy projectile head to the player's position with constant speed

How can I dynamically set the movement speed of the X and Y of the projectile so that it moves at a constant speed when the projectile heads at the player's position? I know this has something to do ...
221 views

### Unity 3D - Confine a gun rotation within certain degrees

I am having troubles making my gun rotate up and down, and have limits, for example, I want the down limit to be 0 degrees, and the up limit to be 90 degrees. Currently I can't figure out how to ...
66 views

### libgdx Vector.cpy question

Why do people use this: public void set(Vector2 v) { this.vector2 = v.cpy(); } insted of just using: public void set(Vector2 v) { this.vector2 = v; } What I don't know that I should know?...
1k views

### How can I pass a std::vector<Vector3f> to my shader?

I have a Vector3f type which has x, y, and z properties. I have a std::vector of these vertices which describe my terrain. I would like to pass these values to a vertex shader through a uniform ...
131 views

### Rotate an arrow on a plane?

I'm creating a display for a GPS-based embedded system and would like to have an arrow indicating the current bearing. I'd love the arrow to have a 3d appearance by rotating it on a plane tilted up ...
95 views

### Reflection velocity

I'm trying to get a moving circular object to bounce (elastically) off of an immovable circular object. Am I doing this right? (The results look right, but I hate to trust that alone, and I can't ...
224 views

### Eculidean space and vector magnitude

Below we have distances from the origin calculated in two different ways, giving the Euclidean distance, the Manhattan distance and the Chebyshev distance. Euclidean distance is what we use to ...
559 views

### How can I project a vector on another vector?

I have a generic not normalized Vector3 v1 and I want to calculate its component along another Vector3 v2. I used to normalize the vector I want to be the direction and then multiplying the other ...
4k views

### Using atan2 to calculate angle between two vectors

I understand that: atan2(vector.y, vector.x) = the angle between the vector and the X axis. But I wanted to know how to get the angle between two vectors using atan2. So I came across this solution: ...
588 views

I created my circle vs. rectangle method based on this algorithm: http://stackoverflow.com/questions/401847/circle-rectangle-collision-detection-intersection Currently, I have a dynamic ball with ...
221 views

### Confusing with an articles wording on Clamping a Vector2

I have been reading an article on Collision Detection and how to resolve it. http://www.wildbunny.co.uk/blog/2011/04/20/collision-detection-for-dummies/ In the section describing an AABB vs Circle, ...
2k views

### Unity: parallel vectors and cross product, how to compare vectors

I read this post explaining a method to understand if the angle between 2 given vectors and the normal to the plane described by them, is clockwise or anticlockwise: public static AngleDir ...
646 views

### Trouble with SAT style vector projection in C#/XNA

Simply put I'm having a hard time working out how to work with XNA's Vector2 types while maintaining spatial considerations. I'm working with separating axis theorem and trying to project vectors onto ...
1k views

### Interpolation between two 3D points?

I'm working with some splines which define a path a character follows (you can see a gameplay video here to get a better understanding of what's going on: http://www.youtube.com/watch?v=BndobjOiZ6g). ...
194 views

### Vectors and corners of squares

I am having some problems with some vector math. Imagine a square and coming from each corner of the square is an invisible vector, which starts at the square's centre and ends at the edge of the ...
2k views

### how to create a Quaternion from an Orientation Vector in xna

i have a Vector3 represents an Orientation in 3D , how to convert it to the corresponding Quaternion ? is there any quick way ? EDIT : i want to add an angular velocity vector to the Orientation ...
526 views

### Get intersection of vector in the middle of the screen

My screen resolution is 640x480 and I have two Vector2 objects located at (10,10) and (600, 320). How can I connect these two objects and extend the line to encompass the whole screens width, how can ...
54 views

### Simulating elastic ball collisions quickly escalates to disaster

I'm trying to learn HTML canvas and was working on a basic physical simulation, where a number of balls are drawn and set in motion, and the program simulates them colliding and bouncing off the walls ...
78 views

### Should I store local forward/right/up vector or calculate when necessary?

I'm working on an object picking and translation/rotation/scale gizmos system in my engine where you select objects and perform transformations on them in a 3d editor-like fashion (e.g. Blender) In ...
44 views

### Vector out of range (Batch rendering & opengl)

So ive (tried to) implement a batch rendering system, and at the for loop the error pops up and I'm not shure what ive done wrong. Any suggestions to improve the system would be much appreciated. (It'...
223 views

### 2D Rendering Based On Y Coordinates

I'm trying to build an RPG worldbuilder. I have seperate classes for images. Like this. Object1::Object1(int x, int y, CSDL_Setup *sdl_set, int *p_CamX, int *p_CamY) { X_pos = x; Y_pos = y; ...
50 views

### Why can't CSS Sprites handle vectors?

Almost all the documentation available either says that "sprites are bitmaps" or that "css sprites must be bitmaps". Is there a specific reason for this? Is it, in fact possible to create a css sprite ...
2k views

### How to rotate an object to face another in Unity?

I'm having an issue where I can't seem to rotate my bullet appropriately whenever I spawn one. I currently have a capsule prefab I am testing with. I spawn it with the following code. ...
150 views

### Averaging normals, or tangents

I am using a library to load an obj but it doest compute the tangets for each vertex, which I need for normal mapping and pom. I computed my tangets, and bitangents, everything appears to be fine, but ...
49 views

### Vector magnitude in orientation

First, a quick overview of my problem: I have a game entity which has a quaternion to represent its rotation/orientation. It also has a 3D vector in world space for its linear velocity. From the ...
113 views

### How to get the normal that points *out* of a polygon

In 2D, each vector (x, y) has two normals: (-y, x) and (y, -x), pointing in opposite directions. Say I have a polygon and for each of it's edges I need to get the normal pointing outwards. In the ...
2k views

### How to move Vector2 along angle?

These are my Vector2's that I am using for this function. public Vector2 position = new Vector2(); public Vector2 velocity = new Vector2(); public Vector2 movement = new Vector2(); public Vector2 ...
381 views

### Adding an angle variance to a 3d vector

I am converting a particle emitter from 2d to 3d. In the 2d system the original coder used a random angle variance and added it to the angle. So it would be something like: thisAngle = emitterAngle ...
169 views

### 3D vector graphics - maintaining correct Z 'length'

So I'm trying to build myself a 3D display 'engine', or whatever it ought to be called. I've been experimenting with PyGame, as it's familiar to me. In a way this has almost been more an excuse to ...
159 views

### Twitchy sprite movement

I'm having an issue with sprite movement, and I'm not sure how to deal with it. When I set a destination for my player sprite (by clicking the screen), it sets the player moving in that direction. ...
941 views

### How to simulate acceleration and then deceleration?

Currently I am only using deceleration. Here is how I do it I need to cover Vector(x,y) unit distance to reach B from A. I simply do - rendering loop-> position = A + Vector(x,y).scale(factor); ...
467 views

### Finding vectors with two points

We're are trying to get the direction of a projectile but we can't find out how For example: [1,1] will go SE [1,-1] will go NE [-1,-1] will go NW and [-1,1] will go SW we need an equation of ...
891 views

### 2D Top down acceleration vector

I have been wanting to solve the issue of movement once and for all... with all that I have learnt and read through, should be a piece of cake one would have thought... , seems it isn't. Having ...
554 views

### How do I get the axes for SAT collision detection

In SAT collision detection how do I calculate the axes for projection?
859 views

### how can i get rotation vector from matrix4x4 in xna?

i want to get rotation vector from matrix to realize some parent-children system for models. Matrix bonePos = link.Bone.Transform * World; Matrix m = Matrix.CreateTranslation(link.Offset) * ...