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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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, ...
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Arma 3 - 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
67 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 ...
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When use LookAt or Inverted world matrix to compute View Matrix?

I am reading this article http://www.3dgep.com/understanding-the-view-matrix/ and it says that View Matrix is the inverted matrix of World (or Model) Matrix but in the first approach the article ...
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1answer
52 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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2answers
62 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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1answer
27 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 ...
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1answer
62 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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4answers
207 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 ...
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46 views

How to convert Screen-space translation into World-space translation

private void Translate(SceneMouseMoveEventArgs args) { var camera = args.Camera; origin_screenspace = camera.UnProject(_position).Xy; cursor_screenspace = new ...
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3answers
122 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 ...
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1answer
82 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 / ...
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94 views

Basic Line of Sight - Pygame

I'm working on a very basic platformer. All objects are rectangles. I've been looking for a simple way to determine if the line of sight is obstructed between Player and CPU by a platform. I saw ...
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1answer
45 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 ...
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1answer
157 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
56 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 ...
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3answers
1k 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 ...
3
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1answer
447 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
50 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
804 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 ...
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2answers
718 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
185 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 ...
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3answers
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Are there 3D projections other than orthographic and perspective? [closed]

The question is pretty much in the title. Are there notable 3D projections other than orthographic and perspective that could be used in a 3D system such as OpenGL? In particular, are there any that ...
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2answers
669 views

How to implement a simple bullet trajectory

I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which ...
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1answer
61 views

Understanding dot notation

Here's my interpretation of dot notation: a = [2,6] b = [1,4] c = [0,8] a . b . c = (2*6)+(1*4)+(0*8) = 12 + 4 + 0 = 16 What is the significance of 16? Apparently it's a scalar. Am I right in ...
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177 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 (u,v,w) and I need the normalized direction vectors of the its two arrow ...
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2answers
1k views

How can I get a direction vector from a an Euler angle?

Im trying to get a directional vector from an euler angle. But im not getting how to do it. This is what i got so far. escapeAngle += 90; var radians = escapeAngle * (Mathf.PI / ...
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1answer
1k views

Gerstner wave function simplified?

The gerstner wave function is a commonly used method to calculate waves and simulate water in video games and movies or most 3d simulations. It is however quite complex so it is very hard for young ...
2
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1answer
559 views

3d Water Simulation formula questions

I have created a Grid: At each point along the grid, is a vertex (Intersection Points): Each of these points has an x,y,z position. Vector3f(x,y,z). In an attempt to animate the grid into a group ...
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3answers
2k views

Move player to mouse click

Im hopelessly not good at algebra and such. But im trying to learn. I want to learn and understand how to use it in game programming rather than modifying snippets or using classes that do it for me. ...
2
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2answers
227 views

Angle between two planes

I have two triangles in 3d space which share 1 edge and I would like to determine if the angle between their normal vectors is "uphill" or "downhill". In other words, if you set one flat, would the ...
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1answer
123 views

Can not seem to adjust the speed of my Car

I'm programming in C++, rendering in OpenGL and using GLM for matrix/vector manipulation and I have implemented very (very) basic car controls; ignoring many forces that are present in reality. Since ...
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1answer
2k views

Basic Car Movement, Converting 2D Vectors to 3D problems

I'm trying to follow this guys method for steering a basic car. Link. It's the first example I can sort of get my head around and I'm trying to convert it to a working 3D version. To get some scope, ...
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1answer
103 views

Using versors for movement

The context I was thinking of using a versor + velocity field to implement the "moving" part of a 2D game object. For example, if the player should move right I just set the versor to be: [1, 0] and ...
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1answer
904 views

shadow mapping and linear depth

I'm implementing ominidirectional shadow mapping for point lights. I want to use a linear depth which will be stored in the color textures (cube map). A program will contain two filtering techniques: ...
3
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1answer
170 views

How to calculate where specular highlights converge with an anisotropic shader?

If you look at a rendering with an anisotropic shader applied you will notice that there are special spots on the 3D surface/mesh where the lights seems to converge, a point where a given vector ...
2
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1answer
319 views

How to correctly represent a bone system?

I'm currently representing my bone system as follows, in pseudocode: root = {} root.rot = v3(0,0,0) root.pos = v3(0,0,0) function create_child(parent,rot,length): child_bone = {} ...
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1answer
162 views

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 ...
2
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1answer
152 views

Getting half plane direction relative from cam position

Im implementing certain Camera movements in my turn based games. I'm able to place and rotate the camera between two units that attack each other. However it will always move to the same "side". Which ...
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1answer
225 views

Optimising skeletal animation

I am implementing a skeleton system for my latest game. I am using my own linear algebra classes which already have some optimisations, such as separate transformPoint and transformVector functions ...
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2answers
207 views

JavaScript “Floats”, or ThreeJS wrong positioning? [closed]

I want to learn how to use Vectors with 3D. Here is a strange Error I have encountered today. Instead of stopping exactly on the other Cube, I get this: When I change the IF to (cube.position.y ...
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2answers
103 views

Should I negate a variable or use absolute value? [closed]

this is how i was chaning ball postion if(...) //if ball goes to left of screen dx = -dx if(...) //if ball goes right of screen dx = -dx; i found some people using math.abs to move ball ...
2
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2answers
346 views

Java Tetris - Matrix Rotations

I'm building Tetris in Java and am trying to use linear algebra to rotate a piece composed of 4 tiles. My friend was explaining the way to do it is: He said: "To clarify, you do need to rotate ...
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3answers
2k views

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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2answers
194 views

How to rotate one object around another moving object in 3-d?

i was wondering if anyone could give me some advice on how to rotate one object around another moving object. After a bit of googling i found some code on another website that worked perfectly but it ...
5
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1answer
696 views

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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2answers
2k views

How can you extract orientation from a transformation matrix?

I have a 4x4 transformation matrix M, and I want to find out the shape of a sphere when transformed by M. (Sphere is at the origin and has radius 1.) I know I can find the center by just multiplying ...
2
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2answers
431 views

2D field of view detection inverted

I'm not sure if the title matches what I'm actually facing I'm trying to test if I can see a point is in my field of view (in the context of an NPC seeing in it's direction.) I know that: cos0 = ...
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2answers
858 views

Matrix Rotation with three Angles

I want to rotate a form with three given angles fo each of the three axis. But the GLM rotation function takes only one angle and a vector as arguments. How can I convert between both formats?
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1answer
2k views

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 ...