# Tagged Questions

Rotation is the circular movement of an object around a specific axis.

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### How can I rotate about an arbitrary point in 3D (instead of the origin)?

I have some models that I want to rotate using quaternions in the normal manner, except instead of rotation about the origin, I want it to be offset slightly. I know that you don't say, in 3d space, ...
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### Turning a sprite such that it rotates in the direction that's most efficient

I have a sprite that moves from waypoint to waypoint. It turns to face its velocity vector, but not instantly (there's a rotation speed). The problem I'm having is, from one direction to another, the ...
26k views

### How can I orbit a camera about it's target point?

I'm drawing a scene where the camera freely moves about the universe. The camera class keeps track of the view (or look at) point, the position of the camera, and the up vector. These vectors/points ...
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### How to rotate an object around world aligned axes?

I have a Vector3 which has an euler angle for each axis. Usually, when I want to create a rotation matrix I will use functions such as D3DXMatrixRotationX passing the respective angle from my ...
14k views

### How can I move a sprite in the direction it is facing?

I'm using Java/Slick 2D. I'm trying to use the mouse to rotate the sprite and the arrow keys to move the sprite. I can get the sprite to rotate no problem, but I cannot get it to move in the direction ...
180 views

### How should I rotate vertices around the origin on the CPU?

I have tried using glm::rotate and such. glm::translate works fine, but rotate doesn't work (if I rotate before/after a translation). Here is my current setup: glm::vec4 Off = glm::vec4(0, 0, 0, 1); ...
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### How to avoid gimbal lock

I am trying to write code with rotates an object. I implemented it as: Rotation about X-axis is given by the amount of change in y coordinates of a mouse and Rotation about Y-axis is given by the ...
1k views

### How do I make an object face the mouse position, but only on one plane?

I want a game object to turn and look towards where the mouse was clicked (in world space). It works well when considering all 3 dimensions, but I really only care for the plane formed by the x and z ...
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### per pixel based collision detection

I was wondering if anyone had any ideas on how to get per pixel collision detection for the android. I saw that the andEngine has great collision detection on rotation as well but couldn't see where ...
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### Arbitrary Rotation about a Sphere

I'm coding a mechanic which allows a user to move around the surface of a sphere. The position on the sphere is currently stored as theta and phi, where theta is the angle between the z-axis and the ...
38k views

### Rotate an object smoothly on the Y axis in Unity

I am attempting a simple script to swing a door open in Unity. This requires a smooth rotation of 90 degrees around the Y axis. I have seen that one way to do this is using Unity's Quanternion ...
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### Why is the camera tilting around the z axis when I only specified x and y?

My goal is to program a camera to point towards the mouse cursor. I attached the following script to the Main Camera. using UnityEngine; using System.Collections; public class CameraController : ...
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### How to keep my Quaternion-using FPS camera from tilting and messing up?

I am using an FPS-like camera, and it uses quaternions. But, whenever I try looking up and then sideways, it tilts, and sometimes it can turn upside down. How can I fix this?
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### Why is my sprite displayed offset from its Box2D body?

I found out about this using a debug renderer. When the game starts, everything is in order. But when a collision happens, the sprite's rotation is way larger than its body. The sprite and body match ...
3k views

### Movement and rotation of bodies in top down game

We are developing a 2D top down game with libgdx using the included box2d as physics engine. We don't want our bodies to accelerate but to instantly move with the wanted velocity. The bodies are ...
2k views

### How to Align Gun with Bullets

I have a top-down 2D shooter. I have an image of a player holding a gun, that rotates to face the mouse. Please note that the gun isn't a separate image tethered to the player, but rather part of the ...
6k views

### Cocos2d rotating sprite while moving with CCBezierBy

I've done my moving actions which consists of sequences of CCBezierBy. However I would like the sprite to rotate by following the direction of the movement (like an airplane). How sould I do this with ...
5k views

### How do I rotate a sprite so that it is 'pointing' in the direction it is moving?

I have a sprite, e.g a missile, heading in a certain direction (using a velocity vector). How do I figure out its how much to rotate it so that it gets drawn 'pointing' in the direction it is heading?...
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### How to calculate origin and position of a weapon which should be “in hands”?

I'm currently stuck with my game, which is from the top perspective. I'm currently using these sprites for player: (using the second at the top): And here's what I use for my gun My problem is ...
1k views

### Arcball Problems with UDK

I'm trying to re-create an arcball example from a Nehe, where an object can be rotated in a more realistic way while floating in the air (in my game the object is attached to the player at a distance ...
148 views

### Quaternion rotation problems [duplicate]

I want to rotate my model and I have X and Y rotations. Here is my code: D3DXQUATERNION q, qrotation; D3DXQuaternionRotationAxis(&q, &D3DXVECTOR3(1.0f, 0.0f, 0.0f), m_matrixRotX*0....
1k views

### How To Approach 360 Degree Snake

I've recently gotten into XNA and must say I love it. As sort of a hello world game I decided to create the classic game "Snake". The 90 degree version was very simple and easy to implement. But as I ...
2k views

### Moving a rotated model in XNA

This seems like a simple problem with an equally simple solution that is invisible to me. I have a model that spawns at the origin and looks at my player model wherever it goes. I would like it to ...
509 views

### Inverting matrix then decomposing gives different quaternion than decomposing then inverting the quat

I'm getting different signs when I convert a matrix to quaternion and invert that, versus when I invert a matrix and then get the quaternion from it: Quaternion a = Quaternion.Invert(getRotation(m)); ...
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### 3d game math problem [duplicate]

i'm very much new to 3d math operations. I know how to rotate 3d points certain degrees arbitrarily by any axis but we were given a strange problem to think on. I'll spare using actual numbers on it,...
3k views

### How can I make my player move in the direction the camera faces?

I have a 3rd person camera which can rotate around the player. My problem is that wherever camera is facing, players forward is always the same direction. For example when camera is facing the right ...
321 views

### Keep Mini map static after rotating / zooming with camera

Hi I am making a 2D game, where the Camera is able to rotate / zoom in or out on the camera focus (the player usually). However my game also contains a mini-map, and so far whenever I have to rotate ...
3k views

### Calculating the rotational force of a 2D sprite

I am wondering if someone has an elegant way of calculating the following scenario. I have an object of (n) number of squares, random shapes, but we will pretend they are all rectangles. We are ...
9k views

### How to rotate blocks in tetris

I have a gameboard grid which is 20 rows high and 10 columns wide with the origin (0,0) being in the top left hand corner. I have a tetrimino in play, which is composed of four blocks. I have the x,y ...
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### How do I rotate a structure of hexagonal tiles on a hexagonal grid?

My 2D isometric game uses a hexagonal grid map. In reference to the image below, how do I rotate the light blue hexagon structures by 60 degrees around the pink hexagons? EDIT: Main hex is (0,0). ...
3k views

### How to implement friction in a physics engine based on “Advanced Character Physics”

I have implemented a physics engine based on the concepts in the classic text Advanced Character Physics by Thomas Jakobsen. Friction is only discussed very briefly in the article and Jakobsen himself ...
7k views

### How do I make an entity move in a direction?

I have an Entity instance which is updated every game tick. Let's just assume that entity moves forward constantly. I'd like to be able to give the entity's angle to a function that makes it move in ...
14k views

### How to calculate a 3x3 rotation matrix from 2 direction vectors?

I've got 2 direction vectors, for the X axis and the Y axis of the object. How do I calculate the rotation matrix of the object using these?
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### How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based ...
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### Render 3d object to 2d surface (embedded system)

i am working on an embedded system of a sort, and in some free time i would like to test its drawing capabilities. System in question is ARM Cortex M3 microcontroller attached to EasyMX Stellaris ...
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### How do you calculate the rotational velocity of a flying object?

When a arrow shaped object is fired it slowly adjusts it's rotation to match the direction it is moving. But what is the actual physics behind it? The question is: How many degrees does the ship ...
1k views

### 360+ degree rotation skips back to 0 degrees when using Math.Atan2(y, x)

I'm new to XNA and this is my first actual project, so forgive my noobness. I'm using jointAngle = System.Math.Atan2(RightStick.Y, RightStick.X); in order to set an angle of a joint (farseer) so ...
6k views

### How to make something rotate a certain amount over an exact amount of time

I'm trying to make a plane rotate down a certain amount and 180 degrees horizontally over 2 seconds. Basically I want it to take the plane 1 second to rotate to a horizontal-facing angle, then take ...
2k views

### Can I use SpriteBatch when drawing sprites on a rotating 3D plane

I'd like to have my plane of sprites rotate similarly as in this game (YouTube Video). So basically, everything is drawn in 2D, but the 2D plane is then "rotated in 3D" (or camera is rotated). When ...
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### How to compute a transformation matrix that describes each position and rotation on a sphere?

I am having an issue constructing my transformation matrices, for this sphere problem. I know the 3d coordinate of the center, and the radius of, the sphere. Since I know the radius and center ...
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### Transformation order when dealing with Meshes

I have created a player model out of primitive types. To do this I have created a Model class and Component (mesh) class. Each model consists of one or more components my problems start when you have ...
297 views

### Keeping rotation between two objects

In my XNA game I have two objects that collide. When the first object collides with the other it is able to latch on to it and move it about the world. I am having a problem with the math here (Math ...
1k views

### Simple thruster like behaviour when rotating sprite

I'm prototyping some 2D game concepts with XNA and have added some basic keyboard inputs to control a triangle sprite. When I press key up the sprite accelerates in it's current facing direction, ...
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### I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to ...
1k views

### How to derive euler angles from matrix or quaternion?

Currently working on steering behavior for my AI and just hit a little mathematical bump. I'm in the process of writing an align function, which basically tries to match the agent's orientation with ...
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### Jittery Movement, Uncontrollably Rotating + Front of Sprite?

So I've been looking around to try and figure out how I make my sprite face my mouse. So far the sprite moves to where my mouse is by some vector math. Now I'd like it to rotate and face the mouse as ...
1k views

### How can I make a sprite move in the direction it's facing using radians?

I am using PGELua for the PlaystationPortable. I would just like to know how to make a 2D sprite move in the direction that the sprite is facing. When the sprite is blitted to the screen it should ...
4k views

### XNA SpriteBatch.Draw with rotation, scaling and origin?

I use a 1x1 pixel 2d texture as source for SpriteBatch.Draw. The texture is scaled and rotated around an origin. The left image is only scaling. The right one scaling + rotation around the origin at ...