Weird Rotation values updating from bullet

[QProgrammer]

Hello

I am using Bullet physic in my simulation.
I have a cylinder at pos(0,0,0) and rotation(0,0,0)

Then i apply an angular velocity to Cylinder to make it rotating over Y axis :

Code: Select all

 
btScalar AngVelocity = 1;
CylinderRigidBody->setAngularVelocity(btVector3(0,AngVelocity,0));
 

Everything is fine and cylinder rotates as expected.

Problem is this :

I expect to cylender rotation change like this :
(0,1,0) > (0,2,0) > ....... > (0,90,0) > ( 0,91,0 ) > (0,92,0) > (0,93,0) > .....>(0,180,0)....... (0,269,0 ) > (0,270,0)

But, what i get is like this :
(0,0,0) > (0,2,0) > ....... > (0,90,0) > (180,89,180) > (180,88,180 ) >(180,87,180)>.... (180,0,180)>.....(180,-89,180)->(0,-90,0)->(0,-89,0)....

For example instead of (0,91,0) , node rotation is (180,89,180) which make no difference in rendering time, but it cause some Irrlitch functions not to work correctly. (for example RotationToDirection())


This difference happens when i update nodes rotation on scene according to Bullet rigidbodu transformation

I tried these two methods :

Code: Select all

1-
    vector3df Euler;
    const btQuaternion& TQuat = TObject->getOrientation();  
    quaternion q(TQuat.getX(), TQuat.getY(), TQuat.getZ(), TQuat.getW());
    q.toEuler(Euler);
    Euler *= RADTODEG;  
    Node->setRotation(Euler);
 
2-
       irr::core::matrix4 mat;
       irr::f32 * ptr;
       ptr = mat.pointer();
       tr.getOpenGLMatrix(ptr);
       Node->setRotation(mat.getRotationDegrees());

Both of them are working good and i get correct physic simulation in my scene, but Rotation vector is not as simple as i expected.
For example instead of (0,269,0 ) it returns (180,-89,180)


So, is there any solution to update node rotation in a better manner? or simplify Bullet rotation values?

[mongoose7]

So, there's no problem?

The 'w' in a quaternion is a double angle, so the actual angle returned will be in [-90, 90].

[kh_]

Have you seen this before? It is from some of the bullet examples posted (not sure who gets the credit)

/// Converts a Bullet quaternion to an Irrlicht euler angle
void QuaternionToEuler(const btQuaternion &TQuat, btVector3 &TEuler)
{
btScalar W = TQuat.getW();
btScalar X = TQuat.getX();
btScalar Y = TQuat.getY();
btScalar Z = TQuat.getZ();
float WSquared = W * W;
float XSquared = X * X;
float YSquared = Y * Y;
float ZSquared = Z * Z;

TEuler.setX(atan2f(2.0f * (Y * Z + X * W), -XSquared - YSquared + ZSquared + WSquared));
TEuler.setY(asinf(-2.0f * (X * Z - Y * W)));
TEuler.setZ(atan2f(2.0f * (X * Y + Z * W), XSquared - YSquared - ZSquared + WSquared));
TEuler *= core::RADTODEG;
}


worked for me

[QProgrammer]

Have you seen this before? It is from some of the bullet examples posted (not sure who gets the credit)

/// Converts a Bullet quaternion to an Irrlicht euler angle
void QuaternionToEuler(const btQuaternion &TQuat, btVector3 &TEuler)
{
btScalar W = TQuat.getW();
btScalar X = TQuat.getX();
btScalar Y = TQuat.getY();
btScalar Z = TQuat.getZ();
float WSquared = W * W;
float XSquared = X * X;
float YSquared = Y * Y;
float ZSquared = Z * Z;

TEuler.setX(atan2f(2.0f * (Y * Z + X * W), -XSquared - YSquared + ZSquared + WSquared));
TEuler.setY(asinf(-2.0f * (X * Z - Y * W)));
TEuler.setZ(atan2f(2.0f * (X * Y + Z * W), XSquared - YSquared - ZSquared + WSquared));
TEuler *= core::RADTODEG;
}


worked for me

Yes, that's the function i am using. I think should be a way to convert Quaternion To Euler with a normal result between 0-360.
That function returns (180,-89,180) as result for a simple rotation of (0,269,0 ).

[mongoose7]

I shouldn't post twice but ...

What do you mean "normal"? I have already told you that quaternions use a double angle. So 2*theta is in [-180, 180]. Therefore theta is in [-90, 90]. If you want it elsewhere, make the change yourself.

From the purist point of view, quaternions are "normal" and Euler angles are weird. Anyway, look up the definition of Euler angles and you should see that you are not even using them. You're using (Z, X, Y) but Euler angles use something like (X, Y, X).