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Added Quat_FromMtx(). This converts a matrix to a quaternion.

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Quat_FromMtx() added.
This commit is contained in:
Thompson Lee 2016-08-06 23:02:17 -04:00
parent ae0ce14c9d
commit 6eb0cacd0a
2 changed files with 61 additions and 0 deletions
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8
include/c3d/maths.h
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@ -621,6 +621,14 @@ C3D_FQuat Quat_RotateZ(C3D_FQuat q, float r, bool bRightSide);
*/ */
void Mtx_FromQuat(C3D_Mtx* m, C3D_FQuat q); void Mtx_FromQuat(C3D_Mtx* m, C3D_FQuat q);
/**
* @brief Get Quaternion equivalent to 4x4 matrix
* @note If the matrix is orthogonal or special orthogonal, where determinant(matrix) = +1.0f, then the matrix can be converted.
* @param[out] q Output Quaternion
* @param[in] m Input Matrix
*/
void Quat_FromMtx(C3D_FQuat* q, C3D_Mtx m);
/** /**
* @brief Identity Quaternion * @brief Identity Quaternion
* @return Identity Quaternion * @return Identity Quaternion

53
source/maths/quat_frommtx.c Normal file
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@ -0,0 +1,53 @@
#include <c3d/maths.h>
void Quat_FromMtx(C3D_FQuat* q, 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;
//Check the main diagonal of the passed-in matrix for positive/negative signs.
trace = m.r[0].c[0] + m.r[1].c[1] + m.r[2].c[2];
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].c[2] - m.r[2].c[1]) * sqrtTrace;
q->y = (m.r[2].c[0] - m.r[0].c[2]) * sqrtTrace;
q->z = (m.r[0].c[1] - m.r[1].c[0]) * 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].c[0] > m.r[1].c[1] && m.r[0].c[0] > m.r[2].c[2])
{
sqrtTrace = 2.0f * sqrtf(1.0f + m.r[0].c[0] - m.r[1].c[1] - m.r[2].c[2]);
q->w = (m.r[2].c[1] - m.r[1].c[2]) / sqrtTrace;
q->x = 0.25f * sqrtTrace;
q->y = (m.r[0].c[1] - m.r[1].c[0]) / sqrtTrace;
q->z = (m.r[0].c[2] - m.r[2].c[0]) / sqrtTrace;
}
else if (m.r[1].c[1] > m.r[2].c[2])
{
sqrtTrace = 2.0f * sqrtf(1.0f + m.r[1].c[1] - m.r[0].c[0] - m.r[2].c[2]);
q->w = (m.r[0].c[2] - m.r[2].c[0]) / sqrtTrace;
q->x = (m.r[0].c[1] - m.r[1].c[0]) / sqrtTrace;
q->y = 0.25f * sqrtTrace;
q->z = (m.r[1].c[2] - m.r[2].c[1]) / sqrtTrace;
}
else
{
sqrtTrace = 2.0f * sqrtf(1.0f + m.r[2].c[2] - m.r[0].c[0] - m.r[1].c[1]);
q->w = (m.r[1].c[0] - m.r[0].c[1]) / sqrtTrace;
q->x = (m.r[0].c[2] - m.r[2].c[0]) / sqrtTrace;
q->y = (m.r[1].c[2] - m.r[2].c[1]) / sqrtTrace;
q->z = 0.25f * sqrtTrace;
}
}
}