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.
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Need help with getting a direction vector between two given points
I need to find the angle of rotation from a bullet traveling from point A to point B, like in my attached diagram. I tried searching, but I got a little lost in which exact formula to use.
I want to ...
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1answer
33 views
Problem calculating screen point for a point in a 3D world with view matrix and projection matrix
I am trying to calculate the 2D screen point of a 3D world position. For this I use the multiplication ViewMatrix * ProjectionMatrix. But I am not getting good results and I think I am messing up my ...
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1answer
28 views
Can't understand why transformation doesn't work
To make a simple transformation like a rotation I want to use linear algebra -multiplying the vec4 vertex_position by a mat4 transformation
If alpha is the angle of rotation, then the mat4 is ...
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0answers
28 views
How can I calculate a corrected oblique clipping matrix?
This problem has been eating at me for a little while now, and it's extremely frustrating.
Unity calculates culling matrices incorrectly. From the matrix, it seems to generate the actual occlusion ...
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1answer
27 views
Recognize that user has traced a path of vector points with mouse
How can I check if a player has traced a closed vector shape from an arbitrary starting point all the way around to the beginning?
Setup
Given are the vector points A through E, which form a closed ...
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1answer
195 views
Why does a unit vector show direction?
If I have two objects, Person A and Person B, and I want to know if Person B is facing the same direction as Person A; once I have the vectors, how do I use the normalized vector to show direction?
...
22
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3answers
2k views
How can I rotate an object based on another's offset to it?
I have a 3D model of a turret that con rotate around the Y-axis. This turret has a cannon that is significantly off the center of the object. I want the cannon, not the turret, to aim at a specified ...
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1answer
81 views
Calculate distance from the centre to the edge of a cube in OpenGL
I'm trying to calculate the distance between a central point on a cube and anywhere on the surface of the cube, depending on the location of a second 3D point.
I have two vertices in 3D; Q and P. Q ...
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2answers
58 views
Rotating Object parallel to other object
I try to rotate objects in the same direction as a reference object.
Normaly this would be easy:
object1.rotation = reference.rotation
But the same rotation can be expressed with different ...
1
vote
1answer
50 views
Project 3d lines onto plane
I'm trying to wrap my head around coordinate projection, and can't seem to solve the problem I am having. Here is an illustration of it:
The cubes represent 3d space, and the 2 red lines represent ...
1
vote
1answer
67 views
How to get the 2d field of view using dot or atan2?
I tried to implement from this site linear-algebra on how do I check the field of view using dot product. But when I check the angle to the given fov angle, I am not getting the desired result. ...
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1answer
48 views
Pitch/Yaw in circle causes undesired Tilt [duplicate]
I've made my own Camera object, with a forward vector as well as a up vector. I happen to be programming in Android using OpenGL ES 2.0 but I think this question is relevant to all frameworks, it ...
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3answers
89 views
Scaling a rotated rectangle in a given direction
I'm facing an issue when trying to scale a rotated rectangle in a given direction.
In my context, the width and height of the rectangle are based on the texture size multiplied by a scale factor (...
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1answer
166 views
given the position and velocity of an object how can I detect possible Collision?
I'm trying to detect Collision between autonomous moving objects and steer direction if collision is detected. so far I've been following a tutorial and I'm having a hard time to fully understand how ...
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1answer
267 views
Calculate initial velocity for trajectory given duration, launch angle, and distance
I need my entity to go from point A to point B with a given launch angle over a given time.
I've been able to figure out the initial velocity without the constraint of the launch angle, but I can't ...
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0answers
111 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
public Transform other;
void Update() {
...
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1answer
57 views
What are projection independent ways of determining whether a normal is facing the viewer?
A position v and normal n are given in world coordinates. Also there is a view matrix V for world-eye coordinate transition and a projection matrix P for eye-ndc transition. I would like to determine, ...
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3answers
52 views
Velocity Relative To A Vector
So I have a velocity vector b in world space and I have a "pointing" vector a in world space. I need to know how to make the velocity vector to be relative to the "pointing" vector. Better explanation ...
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1answer
329 views
Convert transform from world to local space
I have a hierarchical node system. Given a world space transform, I need to obtain the transform for a specific node in local space.
My Node class has the following method.
public void worldToLocal(...
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1answer
141 views
find Vector2 libgdx
I need to get coorinates of red point. Coordinates are just for example, it would be better to see the common formula. Found code like this, but it gains wrong result.()
Vector2 o = new Vector2(6f,2f)...
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1answer
77 views
Distance between two lines (textbook answer vs practical application)
I'm reading through "Mathematics for 3D Game Programming, and Computer Graphics" as a refresher, and leading in to some more complex real world problems down the line. However, one of the early ...
0
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0answers
25 views
Timed Line Drawing
I'm trying to program a remake of the classic Missile Command Atari game from scratch, but I've run into a problem. So I have a function that can draw a line from one point to another. I figured I ...
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vote
1answer
152 views
Display mesh in front of camera
Im trying to display a mesh in front of the camera and FACING the camera ( I'm developing an small editor in wpf using helix3d).
Pretty much something like this question
I load my mesh into a ...
4
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1answer
313 views
How do splines work?
I've been beginning to work with different kinds of splines (e.g. Bezier, Hermite, B-splines) in some of my work with computer graphics and I am trying to get a grasp of how they work (mathematically ...
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0answers
54 views
Is studying Alternate Coordinate System required game development?
I don't know whether or not this question is fit for Gamedev.Stackexchange, but I would like to know :-
I am new to Linear Algebra. I only want to study those parts of Linear Algebra which would ...
2
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0answers
58 views
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 ...
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1answer
67 views
In unity, how do I rotate a vector in relation to the player?
I am making a radar script in a unity FPS game project I am making for class. I already have a working example of a radar script that works in relation to the player's position. However the rotation ...
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vote
1answer
115 views
Tween - keeping a constant velocity at different distances
I am using a tweening library to move my units around. The problem is that the speed varies depending on the distance that the unit has to move because of the tweening:
var time = 1000;
var tween = ...
1
vote
1answer
36 views
Adjust postion only in X axis
I have two game objects named A and B, just as follows:
I want to move object B to this virtual line without any rotation so that the destination is B' . What I have are transformation of object A ...
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0answers
98 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 ...
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0answers
109 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.
Within this coordinate system, I have 4 points that I would like to define another coordinate system. One ...
0
votes
1answer
63 views
XNA Line to Rectangle Collision return first pixel
I have the following code:
public static bool LineIntersectsRect(Point p1, Point p2, Rectangle r)
{
return LineIntersectsLine(p1, p2, new Point(r.X, r.Y), new Point(r.X + r.Width, r.Y)...
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1answer
98 views
How to calculate height of a thought line over a known spot in 3rd person view?
Assuming a player object with third-person-view is in a 3d room and the center of the screen has a dot - let's call it "cursorTarget".
All I have is the position of the player, the position 5 meters ...
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2answers
2k views
How to find the “up” direction of the view matrix, with GLM
Using OpenGL and the GLM matrix library, I want to translate my camera relative to the world coordinate system. This requires me to compute the necessary view matrix. To initialise the view matrix, I ...
3
votes
1answer
60 views
Finding coordinate in radius
Hello i have two points (Vector3) A and B. And have a radius r
How can i find a coords of point P in a circle by angle?
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votes
2answers
85 views
How to get a pleasant path accelerating to a point
I am having trouble moving an object to a target position with a maximum acceleration limit.
If i just accelerate towards the target the object will fly in a doughnut a few times before hitting the ...
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votes
1answer
59 views
How to calculate coordinates of ball when collided with a wall?
I'm developing a game like bubble shooter and need to implement bounce of ball off the vertical wall. I have the following inputs:
Starting position of bubble: {left: 382, right: 378}
Firing angle in ...
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2answers
131 views
How does collisions caculates when developing game in Build an HTML5 Game book
I don't understand authors login when calculating collisions between two circles (bubbles). Here is the Calculating collisions section.
Author writes:
The bubble being fired follows a set of ...
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votes
4answers
758 views
How do I correctly project a point behind the camera?
I am making a 3D game in which I put an exclamation marker above points of interest.
In order to find out where in the 2D screen should I put my marker, I am manually projecting the 3D point where ...
2
votes
3answers
612 views
Detect if two objects are going to crash
i am working on a car game where i am to create an AI, in the game there are other cars and a few objects moving around that i do not want to crash with, i have the speed, position and direction of ...
1
vote
1answer
267 views
CGVectorMake to move SKNode at a certain speed towards the middle of screen?
I am trying to launch my ball sprite towards the middle of the screen at the same speed every time I launch it.
let vel: CGFloat = 1000
dx = size.width / 2 - ball.position.x
dy = vel - size.height / ...
1
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1answer
78 views
How to figure out a vector based on 2 points that add up to a certain value
I am writing a game in which I am representing a velocity with a vector. I have a starting point and a point that I want the object to move towards at a certain speed. (I need the resulting vector's x ...
1
vote
1answer
459 views
Problem with 2D matrix transform og shapes
I have set myself onto the task of creating a class BaseObject, which represents a graphics object with an associated shape as the member variable shape, which is a pointer an object Polygon. I'll ...
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1answer
137 views
How to represent ray and line segment in parametric form?(Visibility)
I am trying to implement this algorithm but am not sure how I am supposed to represent my ray and my line segments(walls).
For the r_px/r_py do I just use the position of the light? For the r_dx/...
8
votes
3answers
7k views
How can I reverse the effect of a transformation matrix?
I have recently been working on a game with using OpenGL and C++ through GLFW.
In the game I have an airship with a turret mounted on it. The airship moves around in world space coordinates and the ...
4
votes
2answers
1k views
Mixing Perspective and Orthographic Projections?
I'm going to start with some background, so jump to my question at the bottom for the TLDR version.
Problem:
In a Japanese 4gamer article (english translation via Chev on Polycount) explaining some ...
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1answer
57 views
trasformation matrix for model's bones
I was developing an fbx converter for legend of grimrock object model (www.grimrock.net), I just wanted to get the animations cause the rest has been converted by others' tools.
I was reading all of ...
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3answers
3k views
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 ...
5
votes
2answers
1k views
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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0answers
450 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 ...
