56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
|
#include <c3d/maths.h>
|
||
|
|
|
||
|
|
C3D_FQuat Quat_FromMtx(const C3D_Mtx* m)
|
||
|
|
{
|
||
|
|
//Taken from Gamasutra:
|
||
|
|
//http://www.gamasutra.com/view/feature/131686/rotating_objects_using_quaternions.php
|
||
|
|
//Expanded upon from:
|
||
|
|
//http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/
|
||
|
|
|
||
|
|
//Variables we need.
|
||
|
|
float trace, sqrtTrace;
|
||
|
|
C3D_FQuat q;
|
||
|
|
|
||
|
|
//Check the main diagonal of the passed-in matrix for positive/negative signs.
|
||
|
|
trace = m->r[0].x + m->r[1].y + m->r[2].z;
|
||
|
|
if (trace > 0.0f)
|
||
|
|
{
|
||
|
|
//Diagonal is positive.
|
||
|
|
sqrtTrace = sqrtf(trace + 1.0f);
|
||
|
|
q.w = sqrtTrace / 2.0f;
|
||
|
|
sqrtTrace = 0.5 / sqrtTrace;
|
||
|
|
q.x = (m->r[1].z - m->r[2].y) * sqrtTrace;
|
||
|
|
q.y = (m->r[2].x - m->r[0].z) * sqrtTrace;
|
||
|
|
q.z = (m->r[0].y - m->r[1].x) * sqrtTrace;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
//Diagonal is negative or equals to zero. We need to identify which major diagonal element has the greatest value.
|
||
|
|
if (m->r[0].x > m->r[1].y && m->r[0].x > m->r[2].z)
|
||
|
|
{
|
||
|
|
sqrtTrace = 2.0f * sqrtf(1.0f + m->r[0].x - m->r[1].y - m->r[2].z);
|
||
|
|
q.w = (m->r[2].y - m->r[1].z) / sqrtTrace;
|
||
|
|
q.x = 0.25f * sqrtTrace;
|
||
|
|
q.y = (m->r[0].y - m->r[1].x) / sqrtTrace;
|
||
|
|
q.z = (m->r[0].z - m->r[2].x) / sqrtTrace;
|
||
|
|
}
|
||
|
|
else if (m->r[1].y > m->r[2].z)
|
||
|
|
{
|
||
|
|
sqrtTrace = 2.0f * sqrtf(1.0f + m->r[1].y - m->r[0].x - m->r[2].z);
|
||
|
|
q.w = (m->r[0].z - m->r[2].x) / sqrtTrace;
|
||
|
|
q.x = (m->r[0].y - m->r[1].x) / sqrtTrace;
|
||
|
|
q.y = 0.25f * sqrtTrace;
|
||
|
|
q.z = (m->r[1].z - m->r[2].y) / sqrtTrace;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
sqrtTrace = 2.0f * sqrtf(1.0f + m->r[2].z - m->r[0].x - m->r[1].y);
|
||
|
|
q.w = (m->r[1].x - m->r[0].y) / sqrtTrace;
|
||
|
|
q.x = (m->r[0].z - m->r[2].x) / sqrtTrace;
|
||
|
|
q.y = (m->r[1].z - m->r[2].y) / sqrtTrace;
|
||
|
|
q.z = 0.25f * sqrtTrace;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return q;
|
||
|
|
}
|