Quaternion.h

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#pragma once

#include "Vec3.h"
#include "Mat4.h"

struct Quaternion
{
    float w;
    float x;
    float y;
    float z;

    Quaternion() : w(1.0f), x(0.0f), y(0.0f), z(0.0f) {}

    Quaternion(float w, float x, float y, float z) : w(w), x(x), y(y), z(z) {}

    Quaternion(int w, int x, int y, int z) : w((float)w), x((float)x), y((float)y), z((float)z) {}

    float getLength()
    {
        return (float)sqrt((w*w) + (x*x) + (y*y) + (z*z));
    }

    float getDotProduct(Quaternion Qa, Quaternion Qb)
    {
        float dp = Qa.x*Qb.x + Qa.y*Qb.y + Qa.z*Qb.z + Qa.w * Qb.w;
        return dp;
    }

    Quaternion getNormalised()
    {
        Quaternion normalised;
        float length = getLength();
        normalised.w = w / length;
        normalised.x = x / length;
        normalised.y = y / length;
        normalised.z = z / length;
        return normalised;
    }

    void rotate(Quaternion &quat, Vec3 axis, float angle);
        
    Mat4 getMatrix();
};

inline Quaternion operator * (Quaternion q1, Quaternion q2)
{
    Quaternion q3;
    q3.w = (q1.w * q2.w) - (q1.x * q2.x) - (q1.y * q2.y) - (q1.z * q2.z);
    q3.x = (q1.w * q2.x) + (q1.x * q2.w) + (q1.y * q2.z) - (q1.z * q2.y);
    q3.y = (q1.w * q2.y) - (q1.x * q2.z) + (q1.y * q2.w) + (q1.z * q2.x);
    q3.z = (q1.w * q2.z) + (q1.x * q2.y) - (q1.y * q2.x) + (q1.z * q2.w);
    return q3;
}