File content as of revision 3:461a9012682d:

/*
 * @author: Thomas Garcia, 2017
 */

#ifndef __QUATERNION_H
#define __QUATERNION_H

struct vector {
  float x;
  float y;
  float z;
};

struct quaternion {
  float r;
  float i;
  float j;
  float k;
};

/**
 * Normalizes a vector.
 *
 * raw: pointer to the vector to be normalized.
 * unit: pointer to where unit vector dimensions should be stored.
 *
 * returns: length of original vector
 */
float vector_normalize(struct vector *raw, struct vector *unit);

/**
 * Adds two vectors together.
 *
 * v1: pointer to the first vector to be added.
 * v2: pointer to the second vector to be added.
 * result: pointer where the sum of v1 and v2 should be stored.
 */
void vector_add(struct vector *v1, struct vector *v2, struct vector *result);

/**
 * Multiples a vector by a constant.
 *
 * v: pointer to the vector to be multiplied.
 * c: scalar constant to multiply vector by.
 * result: pointer where the c * v should be stored.
 */
void vector_multiply(struct vector *v, float c, struct vector *result);

/**
 * Creates a quaternion representing a rotation.
 *
 * v: unit vector representing the axis of rotation.
 * angle: angle of rotation.
 * result: quaternion representing a rotation of degree angle around the unit vector of v.
 */
void quaternion_create(struct vector *v, float angle, struct quaternion *result);

/**
 * Rotates a vector based on a quaternion.
 *
 * v: vector to be rotated.
 * q: quaternion representing the rotation to be performed.
 * result: The rotated vector.
 */
void quaternion_rotate(struct vector *v, struct quaternion *q, struct vector *result);

/**
 * Multiplies two quaternions together.
 *
 * q1: The first quaternion to be multiplied.
 * q2: The second quaternion to be multiplied.
 * result: q1 * q2.
 */
void quaternion_multiply(struct quaternion *q1, struct quaternion *q2, struct quaternion *result);

/**
 * Returns the roll, given a vector.
 *
 * v: The vector.
 */
float vector_roll(struct vector *v);

/**
 * Returns the pitch, given a vector.
 *
 * v: The vector.
 */
float vector_pitch(struct vector *v);

#endif