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.
16
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5answers
2k 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?
14
votes
1answer
4k 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 ...
11
votes
6answers
3k views
Math topics for 3D graphics programming
I understand that the following math topics are required for 3D graphics programming. I have started doing some of them in my math course. Can someone point me in the direction of a resource that ...
11
votes
3answers
3k views
How do I implement a quaternion based camera?
UPDATE The error here was a pretty simple one. I have missed a radian to degrees conversion. No need to read the whole thing if you have some other problem.
I looked at several tutorials about this ...
11
votes
1answer
726 views
Moving an Object along a Curve while Rotating it
I woud like to move an object along a curve. At particular points on the curve, I wish the object to change speed and rotate itself along its axis.
Imagine an airplane flying to a destination. It has ...
10
votes
2answers
920 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 ...
9
votes
2answers
2k 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, ...
9
votes
1answer
1k views
Quaternions and rotation around world axis
Disclaimer: I am a professional games programmer, and use quaternions most days but they are close to black magic to me. I am relatively at home with math but imaginary numbers always confused me. I ...
8
votes
2answers
572 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 ...
7
votes
3answers
414 views
Routes on a sphere surface - Find geodesic?
I'm working with some friends on a browser based game where people can move on a 2D map. It's been almost 7 years and still people play this game so we are thinking of a way to give them something ...
7
votes
2answers
846 views
Calculating a quaternion so a bone points in a specified direction
In an attempt to solve this question, I decided to figure out the absolute (world space) directions of each joint in the source pose (as normalized unit vectors), and then rotate the joints of the ...
5
votes
2answers
362 views
How do I extract a translation vector from a dual quaternion?
I'm trying to do some things with rigid body dynamics using dual quaternions (these are not the same thing as normal quaternions!) and I'm so close to getting things to work. The problem I'm having is ...
4
votes
5answers
1k views
Rotating vector3 by a quaternion
I am attempting to rotate a vector3 by a given quaternion.
I know that this is true
v' = q * v * (q^-1)
I know that q^(-1) is the inverse which just -q/magnitude(q), but how do I map the ...
4
votes
3answers
512 views
Problem representing torque as a quaternion
Euler angles are much more intuitive to me than quaternions for representing 3-dimensional rotations. In fact, I barely understand quaternions at all. I use quaternions for rotation because people ...
4
votes
1answer
284 views
Why game engines usually don't offer a vector3.rotate method? [closed]
Game engines like Three.js, Ogre3d and Unity3d often don't provide a default rotate method on their vector class. You usually have to do something like:
rotated = vector.applyQuaternion(
new ...
4
votes
2answers
281 views
Matrix interpolation for animation blending
I use the XNA Animation Component library to perform blending between animations. It uses spherical linear interpolation between matrices.
In most cases this works without problems. However, I have ...
4
votes
1answer
72 views
Quaternion handedness issue
At least I think it is. I have the following functions:
kmQuaternionRotationAxis - Constructs a Quaternion from an axis and angle
kmMat4RotationQuaternion - Constructs a 4x4 matrix from a quaternion
...
4
votes
1answer
428 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 ...
3
votes
3answers
798 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?
3
votes
2answers
205 views
Rotating voxels in 3d space amongst the x axis
I have a very simple voxel engine and so far it works based on coordinates, e.g. x, y, z. I was wondering if there is a formula for rotating groups of voxels/coordinates from the x axis(e.g. [0, 1, ...
3
votes
2answers
107 views
Calculating transform of arrow model pointing at some point in 3D space
I'm working on a 3D flight game and I'd like to implement a simple "navigation arrow" pointing at the next waypoint in world which the player has to fly to.
I have position of both airplane (=camera) ...
3
votes
1answer
199 views
D3DXMatrixDecompose gives different quaternion than D3DXQuaternionRotationMatrix
In trying to solve this problem, I tracked down the problem to the conversion of the rotation matrix to quaternion. In particular, consider the following matrix:
-0.02099178 0.9997436 -0.008475631 0
...
3
votes
2answers
572 views
Quaternion understanding
I have some understanding problem concerning quaternions.
In order to have my world object rotate in the correct way, I need to invert their quaternion rotation while refreshing the object world ...
3
votes
1answer
89 views
What is the rationale behind this method of computing the w-component from MD5 mesh files?
In tutorials regarding the MD5Mesh format, like this one, we often see code like
float t = 1.0f - (q.x * q.x) - (q.y * q.y) - (q.z * q.z);
if (t < 0.0f) {
q.w = 0.0f;
} else {
q.w = -sqrt ...
3
votes
2answers
297 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 ...
3
votes
1answer
49 views
How to map absolute Joystick position to object rotation?
In my (Ogre) 3d scene I have an object that should be rotated locally based on Joystick input. I have a Joystick with min/max values of [-32767, 32767] on both X and Y axes. When the Joystick is in ...
3
votes
1answer
157 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 ...
3
votes
1answer
345 views
Convert rotation from Right handed System to left handed
I have Euler angles from a right handed system that I am trying to convert to a left handed system. All the information that I have read online says that to convert it simply multiply the axis and ...
3
votes
0answers
289 views
Setting Orientation of Character in Bullet/Ogre [closed]
I've been suffering from an issue regarding the implementation of orienting characters in a game I'm implementing using Ogre3D and Bullet physics.
What I have: A Direction Vector that the character ...
2
votes
3answers
324 views
How should I model exact 90-degree rotations in 3D?
I'm familiar with quaternions... have used them in the past to model arbitrary rotations in 3D, as for a plane flying around with full pitch/yaw/roll freedom. Works great.
Now I'm working on a 3D ...
2
votes
2answers
387 views
Rotate model using quaternion
Currently I have this to rotate my 3D model that rotates on it's local axis independent from the world's axis:
// Rotate model with Right Thumbstick
modelRotation -= pController.ThumbSticks.Right.X * ...
2
votes
1answer
643 views
Quaternion Camera Orbiting around a Sphere
Background: I'm trying to create a game where the camera is always rotating around a single sphere. I'm using the DirectX D3DX math functions in C++ on Windows.
The Problem: I cannot get both the ...
2
votes
2answers
370 views
Quaternion based rotation and pivot position
I can't figure out how to perform matrix rotation using Quaternion while taking into account pivot position in OpenGL.What I am currently getting is rotation of the object around some point in the ...
2
votes
2answers
393 views
Quaternions - how to limit axis?
Is there any possibility to limit quaternions to move only in x & y axis (like in Eulers- yaw and pitch, without rolling)? I's there any equation or something similar to do this?
Some example:
...
2
votes
1answer
301 views
Finding a suitable axis-angle to avoid gimbal lock
In OpenGL the camera faces the -z axis with the +y axis pointing up. I am using quaternions to represent the orientation of my objects (which works well) and am trying to do the same for the camera. I ...
2
votes
2answers
1k views
Quaternion rotation
I have a problem understanding quaternions rotation in OpenGL.
So far I have implemented all function and operators related to quaternions.They are definitely working right!.
However I can't find ...
2
votes
1answer
503 views
Rotating a vector by a quaternion
I am trying to rotate a direction vector (0,0,1,0) by a rotation quaternion in DirectX.
From what understanding, to rotate the vector you must do
NewVector = rotQuaternion * Vector * ...
2
votes
2answers
1k views
How do I correctly use dual quaternions for rotation and translation of an object?
Up until now I've handled a given object's rotation and translation separately using normal quaternions for rotation and vectors for translation. However I'd like to use dual quaternions to handle ...
2
votes
2answers
720 views
Why is my quaternion camera rotating around strange axes?
I can't get it to work for the life of me. Its rotating the camera in the global coordinate system, or some other random coordinate system, not the camera local coordinate system. WASDEC work ...
2
votes
2answers
239 views
Rotating a child shape relative to its parent's orientation
When rotating a shape using a quaternion value I also wish rotate its child shape.
The parent and child shapes both start with different orientations but their relative orientations should always be ...
2
votes
1answer
703 views
Flip rotation matrix
I'm doing character control with kinect. I need to mirror the joint orientation because the character faces the player. Somehow by Googling through internet I've done it and everything works very ...
2
votes
1answer
54 views
Rotating and Translating a Node in Horde3D with Matrices and Quaternions
I have been trying to learn how to use the Horde3D rendering engine for the past couple of days,
and so far I have managed to learn a decent amount and integrate Bullet Physics with it as well.
My ...
1
vote
1answer
187 views
How to get a point to the left/right of a vector
I have a position vector of a point in space and a quaternion for it's rotation. What i'm trying to calculate is a point too the left and a point to the right.
I have the position and ...
1
vote
3answers
440 views
Create quaternion based on where a unit is hit (shield effect as in Starcraft 2)
I'd like to implement a shield effect like that done for Protoss units in Starcraft 2. I'm guessing that the technique involved uses a partial sphere that is rotated to reflect where a unit is hit.
...
1
vote
3answers
219 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
2answers
408 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
1answer
1k views
how to create a Quaternion from an Orientation Vector in xna
i have a Vector3 represents an Orientation in 3D , how to convert it to the corresponding Quaternion ?
is there any quick way ?
EDIT :
i want to add an angular velocity vector to the Orientation ...
1
vote
2answers
108 views
Accumulating rotations for camera
It seems there are three ways to store a camera's rotation: in angles, view matrix or quaternion. I was using euler angles since when I used a matrix it had a tendency to accumulate rounding errors ...
1
vote
1answer
82 views
Moving an object toward another object on sphere knowing their quaternions
I have a sphere centered in world origin. On the sphere surface I have two objects and I know their quaternions (rotation around sphere).
Currently my movement works on Vector2 inputs (cannot change ...
1
vote
2answers
245 views
Quaternion Camera
Can someone help me figure out how to use a Quaternion with the PerspectiveCamera in libGDX or in general? I am trying to rotate my camera around a sphere that is being drawn at (0,0,0). I am not sure ...
