Quaternion multiply problem

jesterlecodeur · 2002-02-26T23:58:54

I use this to multiply quaternions: INLINE CQuaternion& MultiplyQuaternion( CQuaternion& qOut, const CQuaternion &qA, const CQuaternion &qB ) { qOut.w = qA.w*qB.w - qA.x*qB.x - qA.y*qB.y - qA.z*qB.z; qOut.x = qA.w*qB.x + qA.x*qB.w + qA.y*qB.z - qA.z*qB.y; qOut.y = qA.w*qB.y - qA.x*qB.z + qA.y*qB.w + qA.z*qB.x; qOut.z = qA.w*qB.z + qA.x*qB.y - qA.y*qB.x + qA.z*qB.w; return qOut; } And this routine to convert quaternions to euler angles: INLINE CVector3& CQuaternion::GetEulerAngles( CVector3& vc ) { float ww = w*w; float xx = x*x; float yy = y*y; float zz = z*z; vc.z = atan2f( 2.0f * (x*y + z*w),(xx - yy - zz + ww)); vc.x = atan2f( 2.0f * (y*z + x*w),(-xx - yy + zz + ww)); // The end is very thrash (the base end routine give the y angles only within [-PI/2, PI/2] ) float cx = cosf(vc.x); float sx = sinf(vc.x); float cz = cosf(vc.z); float sz = sinf(vc.z); float sy = -2.0f * (x*z - y*w) float cy = (x*4.0f*w - cx*sz + sx*sy*cz) / sz; vc.y = asinf( -2.0f * (x*z - y*w) ); if( cy > 0.0f && sy < 0.0f) { vc.y = vc.y + PI; } else if( cy > 0.0f && sy > 0.0f) { vc.y = vc.y - PI; } return vc; } [/souce] The result work but give me some problems. At an instant i have a rotation (in degree) of (0, -89, 0) when i rotate over y of 2° it give me ( 180, 91, 180 ), this situation is symétric for (0,91,0) and (180, -89, 180). The problem is that I always correct the z rotation and when ( 180, 91, 180 ) come, i convert the quaternion to ( 180, 91, 0 ) wich is the opposite direction and absolutly false. Is there a algorithm that give continous values or at least move the problem to another axe or a way to convert GetEulerAngles values ? Thanx. _______________ Jester, studient programmer The Jester Home in French

Math and Physics Programming

Started by jesterlecodeur February 23, 2002 08:00 PM

9 comments, last by jesterlecodeur 22 years, 11 months ago

Fruny

1,658

February 26, 2002 11:58 PM

Join the index of your left hand to that of your right hand as seen from above. Then raise your hands to the level of your eyes. You''ll see the (projected) angle increase.

"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." — Brian W. Kernighan

Quaternion multiply problem

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Quaternion multiply problem

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