Mathematical constructions, number systems. In 3D-graphics quaternions are used alongside vectors and matrices. One of the benefits of quaternions is that they overcome some rotational problems (known as gimbal locks) that are inherent to vectors and matrices.

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21
votes
1answer
11k views

Orienting a model to face a target

I have two objects (target and player), both have Position (Vector3) and Rotation (Quaternion). I want the target to rotate and be facing right at the player. The target, when it shoots something ...
12
votes
2answers
8k views

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, ...
12
votes
2answers
4k views

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 ...
13
votes
2answers
2k views

Why do people use quaternions?

I have been using them as a black box for a while, I'm just learning about of the maths but I'd just like some definitive answers to this question. So far the only benefit I've come across personally ...
10
votes
4answers
4k views

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?
6
votes
1answer
497 views

Walking on a sphere

I'm working on a game which involves walking your character on the surface of a sphere. Using the answer to Arbitrary Rotation about a Sphere, I've written my code as: if (game.isKeyDown(37)) { // ...
4
votes
1answer
965 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 ...
2
votes
3answers
476 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)); ...
1
vote
1answer
120 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), ...
19
votes
6answers
8k views

How can you visualize a quaternion?

When I visualise a three dimensional rotation matrix, or scaling matrix I visualize it as three axes. Is there a similar way that I can visualize a rotation quaternion?
4
votes
1answer
2k views

Quaternion Look At with Up vector

I have implemented a "look at" method for my screen elements and it almost works how I want it to work. The ScreenElement class uses a R3 Vector and a Quaternion to determine the position and ...
4
votes
2answers
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 ...
2
votes
0answers
319 views

How to set object's / node's absolute rotation correctly?

Usually when I want to rotate an object/node in my Ogre scene I call the node's rotate() method. That rotates the node locally relative to it's current rotation. So for example, when I start with 0 ...
2
votes
2answers
642 views

OpenGL Camera causes spatial distortion

I'm trying to implement a 3D camera of the "Orbit around the origin" variety in a game engine I'm developing in order to learn about 3D graphics and game programming. I have a basic handle on the ...
1
vote
0answers
555 views

How to align angular velocity wit target rotation in 3D?

I'm making a space crew sim (controlling a ship) and have recently posted a question about how to calculate ETA between two rotations. I how now a new question more well defined. Background: I have ...
1
vote
1answer
597 views

Rotation matrices from Quaternion.Identity and -Quaternion.Identity are the same?

If I create a rotation matrix from an identity quaternion then it is the same as a creating it from a negative identity quaternion Matrix m0 = ...
0
votes
2answers
76 views

Moving a ship forward from rotation

I am making a simple space simulator, where the player can control a ship using 2 controls, one for pitch and one for bank. The ship is properly rotated but I cannot figure out how to make the ship ...