quaternions

I'm looking for a simple implementation for arcball rotation on 3D models with quaternions, specifically using GLKit on iOS . So far, I have examined the following sources: Arcball rotation with GLKit How to rotate a 3D object with touches using OpenGL I've also been trying to understand source code and maths from here and here . I can rotate my object but it keeps jumping around at certain angles, so I fear gimbal lock is at play. I'm using gesture recognizers to control the rotations (pan gestures affect roll and yaw, rotate gestures affect pitch). I'm attaching my code for the quaternion

I have a rotation quaternion and want to extract the angle of rotation about the Up axis (the yaw). I am using XNA and as far as I can tell there is no inbuilt function for this. What is the best way to do this? Thanks for any help, Venatu The quaternion representation of rotation is a variation on axis and angle. So if you rotate by r radians around axis x , y , z , then your quaternion q is: q[0] = cos(r/2); q[1] = sin(r/2)*x; q[2] = sin(r/2)*y; q[3] = sin(r/2)*z; If you want to create a quaternion that only rotates around the y axis, you zero out the x and z axes and then re-normalize the

I have a quaternion representing the orientantion of an object (yellow box and sphere). I would like to know if it is possible to split that quaternion into other quaternions that give us the rotation of each local axis (X, Y and Z). What I have been doing until now is getting the Euler representation and work with it, but it is not the correct solution for my particular case: Given two points (blue boxes), I want to limit the orientation of my object so that it can't point out of the grey plane, even if my quaternion looks out of that plane. I want to split (decompose) the quaternion, because

In the inspector for a gameObject I'm using the starting rotation is "-90", but when I run print(transform.eulerAngles.x) I get 270 (ditto for transform.localEulerAngles.x ). If I tilt the gameObject downward, the inspector X value gets bigger (say, to -85) as it should. The printed transform.eulerAngles.x also gets bigger, say to 274. Here's where things get weird: If I tilt the gameObject upward the inspector x coordinate gets smaller (ex, to -95), as it should, BUT the printed eulerAngle.x value gets BIGGER (here to 274). So if I rotate the object up or down from the eulerAngle.x being 270,

I am converting angles-axis representation to Euler angles. I decided to check and make sure that the Euler angles I got from the conversion would lead back to the original axis-angle. I print out the values, but they do not match! I have read http://forum.onlineconversion.com/showthread.php?t=5408 and http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles as well as similar conversion questions on this website. In the code below I start with angle 'angle' and axis (rx,ry,rz), then I convert it to quaternions (q0,q1,q2,q3). I convert the quaternions to euler angles (roll,

Hi i'm trying to figure out how to calculate the inverse of a quaternion. A code example would be awesome. Cheers Mihai Maruseac See Wikipedia article for the entire Quaternion math. Don't know what language you want to use but I'll try to give some hints in Haskell. data Quaternion = Q Double Double Double Double deriving (Show, Eq) First, you need to implement multiplication and addition of quaternions. instance Num Quaternion where (+) = q_plus (*) = q_mult --.... q_plus (Q a b c d) (Q a' b' c' d') = Q (a + a') (b + b') (c + c') (d + d') q_mult (Q a b c d) (Q a' b' c' d') = Q a'' b'' c'' d'