# Tagged Questions

3answers
574 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 ...
2answers
598 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 ...
0answers
60 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 ...
0answers
101 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 ...
3answers
1k 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. ...
1answer
90 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 ...
1answer
1k 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, ...
0answers
68 views

### Using Angles (or rotation) with Vectors for Car physics

I've been reading this blog that explains basic linear algebra for game developers and I understand the basics of vector mathematics. I'm using vectors to create a car that simulates the very basic ...
1answer
121 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 ...
1answer
245 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 = {} ...
1answer
149 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 ...
2answers
138 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 ...
3answers
1k 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 ...
1answer
358 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 ...
1answer
1k 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 ...
1answer
134 views

### Is it safe to cast my 2D points to 3D points for a library which only takes Vector3s?

I need to cast a ray in 2D space for bullet collision detection, but the Ray.Intersects method requires a BoundingBox which uses vector3's not vector2's. My question is should I just ignore the Z ...
1answer
484 views

### 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 ...
3answers
2k views

### Rotating a vector by another vector in shader

I have a terrain surface with a normal for each point on the terrain. I have a second detail normal map to be applied to the terrain. These normals are in 3-space. The Y value of both normals is ...
4answers
822 views

### Moving objects colliding when using unalligned collision avoidance (steering)

I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving ...
1answer
1k views

### 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 ...
4answers
3k views

### 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 ...