• Advertisement

Archived

This topic is now archived and is closed to further replies.

Problem with rotation matrix

This topic is 5619 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Ok, I have my matrix and I rotate it via 3 functions. (X, Y, Z) It will rotate it relativ NOT absolute. My Problem is: After each function call the scene got smaller - the axis I rotate gets shrinked - but only this axis - And it is very fast - after about 5 rotations it has nearly half the original size... However the rotations seem to be correct - i think it is not a math problem -> rounding-problem ? here one of the 3 functions
        
// double m[16];

// column-major

void MATRIX4X4::RotateY(const double& RotationY)
{

	double c = cos(RotationY);
	double s = sin(RotationY);

	m[0]  = -m[8]*s +  m[0]*c;
	m[1]  = -m[9]*s +  m[1]*c;
	m[2]  = -m[10]*s + m[2]*c;
	//m[3]  = -m[11]*s + m[3]*c;

    
	m[8]  = m[0]*s + m[8]*c;
	m[9]  = m[1]*s + m[9]*c;
	m[10] = m[2]*s + m[10]*c;
	//m[11] = m[3]*s + m[11]*c;

	
}        
sry for bad english [edited by - TomCat4711 on August 31, 2002 4:28:46 PM]

Share this post


Link to post
Share on other sites
Advertisement
I''m running on about 3 hours of sleep here, but your function looks basically correct. The only thing I see immediately wrong is something you already recognized in your second message. You must use temporary variables when you calculate m[0], m[1], and m[2]. Reason? You need to use the original, unmodified values of m[0], m[1], and m[2] when you calculate m[8], m[9], and m[10] later on. And if you do not use temporary variables you lose the original values. Your code should look like:

new_m0 = calculate using m[]
new_m1 = calculate using m[]
new_m2 = calculate using m[]
m[8] = calculate using m[]
m[9] = calculate using m[]
m[10] = calculate using m[]
m[0] = new_m0
m[1] = new_m1
m[2] = new_m2

Hope that helps!

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

Share this post


Link to post
Share on other sites

  • Advertisement