quaternions.c File Reference

Functions
float	rsqrtf (float x)
	Perform a fast, approximate reciprocal square root.
float	mathsqrtf (float x)
	Perform a fast, approximate square root.
void	mathEulerToQuat (float *q, const float *euler)
	convert euler angles (in radians) to a quaternion.
void	mathQuatApply (float *qout, const float *q1, const float *q2)
	Rotate one quaternion by another (and do not normalize)
void	mathQuatNormalize (float *qout, const float *qin)
	Normalize a quaternion.
void	mathCrossProduct (float *p, const float *a, const float *b)
	Perform a 3D cross product.
void	mathRotateVectorByQuaternion (float *pout, const float *q, const float *p)
	Rotate a 3D vector by a quaternion.
void	mathRotateVectorByInverseOfQuaternion (float *pout, const float *q, const float *p)
	Rotate a 3D vector by the inverse of a quaternion.
void	mathComputeQuaternionDeltaBetweenQuaternions (float *qOut, const float *qFrom, const float *qTo)
	Compute the difference between two quaternions.
void	mathQuatFromTwoVectors (float *qOut, const float *v1, const float *v2)
	Compute the quaterntion rotation between two vectors, from v1 to v2.

Function Documentation

rsqrtf()

float rsqrtf

(

float

x

)

Perform a fast, approximate reciprocal square root.

Parameters

x	The number to take a recriprocal square root of.

Returns

approximately 1/sqrt(x)

mathsqrtf()

float mathsqrtf

(

float

x

)

Perform a fast, approximate square root.

Parameters

x	The number to take a square root of.

Returns

approximately sqrt(x) (but is much faster)

mathEulerToQuat()

void mathEulerToQuat	(	float *	q,
		const float *	euler )

convert euler angles (in radians) to a quaternion.

Parameters

q	Pointer to the wxyz quat (float[4]) to be written.
euler	Pointer to a float[3] of euler angles.

mathQuatApply()

void mathQuatApply	(	float *	qout,
		const float *	q1,
		const float *	q2 )

Rotate one quaternion by another (and do not normalize)

Parameters

qout	Pointer to the wxyz quat (float[4]) to be written.
q1	First quaternion to be rotated.
q2	Quaternion to rotate q1 by.

mathQuatNormalize()

void mathQuatNormalize	(	float *	qout,
		const float *	qin )

Normalize a quaternion.

Parameters

qout	Pointer to the wxyz quat (float[4]) to be written.
qin	Pointer to the quaterion to normalize.

mathCrossProduct()

void mathCrossProduct	(	float *	p,
		const float *	a,
		const float *	b )

Perform a 3D cross product.

Parameters

p	Pointer to the float[3] output of the cross product (p = a x b)
a	Pointer to the float[3] of the cross product a vector.
b	Pointer to the float[3] of the cross product b vector.

mathRotateVectorByQuaternion()

void mathRotateVectorByQuaternion	(	float *	pout,
		const float *	q,
		const float *	p )

Rotate a 3D vector by a quaternion.

Parameters

pout	Pointer to the float[3] output of the rotation
q	Pointer to the wxyz quaternion (float[4]) of the rotation.
p	Pointer to the float[3] of the vector to rotates.

mathRotateVectorByInverseOfQuaternion()

void mathRotateVectorByInverseOfQuaternion	(	float *	pout,
		const float *	q,
		const float *	p )

Rotate a 3D vector by the inverse of a quaternion.

Parameters

pout	Pointer to the float[3] output of the antirotation.
q	Pointer to the wxyz quaternion (float[4]) opposite of the rotation.
p	Pointer to the float[3] of the vector to antirotates.

mathComputeQuaternionDeltaBetweenQuaternions()

void mathComputeQuaternionDeltaBetweenQuaternions	(	float *	qOut,
		const float *	qFrom,
		const float *	qTo )

Compute the difference between two quaternions.

Parameters

qOut	Pointer to the float[4] (wxyz) output of the rotation between qFrom and qTo.
qFrom	is the Quaterntion that you are rotating FROM
qTo	is the Quaternion that you are rotating TO

mathQuatFromTwoVectors()

void mathQuatFromTwoVectors	(	float *	qOut,
		const float *	v1,
		const float *	v2 )

Compute the quaterntion rotation between two vectors, from v1 to v2.

Parameters

qOut	Pointer to the float[4] (wxyz) output of the rotation defined by v1 to v2
v1	is the vector you are rotating FROM. THIS MUST BE NORMALIZED.
v2	is the vector you are rotating TO. THIS MUST BE NORMALIZED.