module raymath;

import raylib;

/**********************************************************************************************
*
*   raymath v1.2 - Math functions to work with Vector3, Matrix and Quaternions
*
*   CONFIGURATION:
*
*   #define RAYMATH_IMPLEMENTATION
*       Generates the implementation of the library into the included file.
*       If not defined, the library is in header only mode and can be included in other headers
*       or source files without problems. But only ONE file should hold the implementation.
*
*   #define RAYMATH_HEADER_ONLY
*       Define static inline functions code, so #include header suffices for use.
*       This may use up lots of memory.
*
*   #define RAYMATH_STANDALONE
*       Avoid raylib.h header inclusion in this file.
*       Vector3 and Matrix data types are defined internally in raymath module.
*
*
*   LICENSE: zlib/libpng
*
*   Copyright (c) 2015-2020 Ramon Santamaria (@raysan5)
*
*   This software is provided "as-is", without any express or implied warranty. In no event
*   will the authors be held liable for any damages arising from the use of this software.
*
*   Permission is granted to anyone to use this software for any purpose, including commercial
*   applications, and to alter it and redistribute it freely, subject to the following restrictions:
*
*     1. The origin of this software must not be misrepresented; you must not claim that you
*     wrote the original software. If you use this software in a product, an acknowledgment
*     in the product documentation would be appreciated but is not required.
*
*     2. Altered source versions must be plainly marked as such, and must not be misrepresented
*     as being the original software.
*
*     3. This notice may not be removed or altered from any source distribution.
*
**********************************************************************************************/

extern (C) @nogc nothrow:

//#define RAYMATH_STANDALONE      // NOTE: To use raymath as standalone lib, just uncomment this line
//#define RAYMATH_HEADER_ONLY     // NOTE: To compile functions as static inline, uncomment this line

import raylib; // Required for structs: Vector3, Matrix

//----------------------------------------------------------------------------------
// Defines and Macros
//----------------------------------------------------------------------------------

// Return float vector for Matrix

extern (D) auto MatrixToFloat(T)(auto ref T mat)
{
    return MatrixToFloatV(mat).v;
}

// Return float vector for Vector3

extern (D) auto Vector3ToFloat(T)(auto ref T vec)
{
    return Vector3ToFloatV(vec).v;
}

// NOTE: Helper types to be used instead of array return types for *ToFloat functions
struct float3
{
    float[3] v;
}

struct float16
{
    float[16] v;
}

import core.stdc.math; // Required for: sinf(), cosf(), sqrtf(), tan(), fabs()

pragma(inline, true):

//----------------------------------------------------------------------------------
// Module Functions Definition - Utils math
//----------------------------------------------------------------------------------

// Clamp float value
static float Clamp(float value, float min, float max)
{
    float result = (value < min)? min : value;

    if (result > max) result = max;

    return result;
}

// Calculate linear interpolation between two floats
static float Lerp(float start, float end, float amount)
{
    float result = start + amount*(end - start);

    return result;
}

// Normalize input value within input range
static float Normalize(float value, float start, float end)
{
    float result = (value - start)/(end - start);

    return result;
}

// Remap input value within input range to output range
static float Remap(float value, float inputStart, float inputEnd, float outputStart, float outputEnd)
{
    float result =(value - inputStart)/(inputEnd - inputStart)*(outputEnd - outputStart) + outputStart;

    return result;
}

//----------------------------------------------------------------------------------
// Module Functions Definition - Vector2 math
//----------------------------------------------------------------------------------

// Vector with components value 0.0f
static Vector2 Vector2Zero()
{
    Vector2 result = { 0.0f, 0.0f };

    return result;
}

// Vector with components value 1.0f
static Vector2 Vector2One()
{
    Vector2 result = { 1.0f, 1.0f };

    return result;
}

// Add two vectors (v1 + v2)
static Vector2 Vector2Add(Vector2 v1, Vector2 v2)
{
    Vector2 result = { v1.x + v2.x, v1.y + v2.y };

    return result;
}

// Add vector and float value
static Vector2 Vector2AddValue(Vector2 v, float add)
{
    Vector2 result = { v.x + add, v.y + add };

    return result;
}

// Subtract two vectors (v1 - v2)
static Vector2 Vector2Subtract(Vector2 v1, Vector2 v2)
{
    Vector2 result = { v1.x - v2.x, v1.y - v2.y };

    return result;
}

// Subtract vector by float value
static Vector2 Vector2SubtractValue(Vector2 v, float sub)
{
    Vector2 result = { v.x - sub, v.y - sub };

    return result;
}

// Calculate vector length
static float Vector2Length(Vector2 v)
{
    float result = sqrtf((v.x*v.x) + (v.y*v.y));

    return result;
}

// Calculate vector square length
static float Vector2LengthSqr(Vector2 v)
{
    float result = (v.x*v.x) + (v.y*v.y);

    return result;
}

// Calculate two vectors dot product
static float Vector2DotProduct(Vector2 v1, Vector2 v2)
{
    float result = (v1.x*v2.x + v1.y*v2.y);

    return result;
}

// Calculate distance between two vectors
static float Vector2Distance(Vector2 v1, Vector2 v2)
{
    float result = sqrtf((v1.x - v2.x)*(v1.x - v2.x) + (v1.y - v2.y)*(v1.y - v2.y));

    return result;
}

// Calculate angle from two vectors in X-axis
static float Vector2Angle(Vector2 v1, Vector2 v2)
{
    float result = atan2f(v2.y - v1.y, v2.x - v1.x)*(180.0f/PI);

    if (result < 0) result += 360.0f;

    return result;
}

// Scale vector (multiply by value)
static Vector2 Vector2Scale(Vector2 v, float scale)
{
    Vector2 result = { v.x*scale, v.y*scale };

    return result;
}

// Multiply vector by vector
static Vector2 Vector2Multiply(Vector2 v1, Vector2 v2)
{
    Vector2 result = { v1.x*v2.x, v1.y*v2.y };

    return result;
}

// Negate vector
static Vector2 Vector2Negate(Vector2 v)
{
    Vector2 result = { -v.x, -v.y };

    return result;
}

// Divide vector by vector
static Vector2 Vector2Divide(Vector2 v1, Vector2 v2)
{
    Vector2 result = { v1.x/v2.x, v1.y/v2.y };

    return result;
}

// Normalize provided vector
static Vector2 Vector2Normalize(Vector2 v)
{
    Vector2 result = { 0 };
    float length = sqrtf((v.x*v.x) + (v.y*v.y));

    if (length > 0)
    {
        result.x = v.x*1.0f/length;
        result.y = v.y*1.0f/length;
    }

    return result;
}

// Calculate linear interpolation between two vectors
static Vector2 Vector2Lerp(Vector2 v1, Vector2 v2, float amount)
{
    Vector2 result = { 0 };

    result.x = v1.x + amount*(v2.x - v1.x);
    result.y = v1.y + amount*(v2.y - v1.y);

    return result;
}

// Calculate reflected vector to normal
static Vector2 Vector2Reflect(Vector2 v, Vector2 normal)
{
    Vector2 result = { 0 };

    float dotProduct = (v.x*normal.x + v.y*normal.y); // Dot product

    result.x = v.x - (2.0f*normal.x)*dotProduct;
    result.y = v.y - (2.0f*normal.y)*dotProduct;

    return result;
}

// Rotate vector by angle
static Vector2 Vector2Rotate(Vector2 v, float angle)
{
    Vector2 result = { 0 };

    result.x = v.x*cosf(angle) - v.y*sinf(angle);
    result.y = v.x*sinf(angle) + v.y*cosf(angle);

    return result;
}

// Move Vector towards target
static Vector2 Vector2MoveTowards(Vector2 v, Vector2 target, float maxDistance)
{
    Vector2 result = { 0 };

    float dx = target.x - v.x;
    float dy = target.y - v.y;
    float value = (dx*dx) + (dy*dy);

    if ((value == 0) || ((maxDistance >= 0) && (value <= maxDistance*maxDistance))) return target;

    float dist = sqrtf(value);

    result.x = v.x + dx/dist*maxDistance;
    result.y = v.y + dy/dist*maxDistance;

    return result;
}

//----------------------------------------------------------------------------------
// Module Functions Definition - Vector3 math
//----------------------------------------------------------------------------------

// Vector with components value 0.0f
static Vector3 Vector3Zero()
{
    Vector3 result = { 0.0f, 0.0f, 0.0f };

    return result;
}

// Vector with components value 1.0f
static Vector3 Vector3One()
{
    Vector3 result = { 1.0f, 1.0f, 1.0f };

    return result;
}

// Add two vectors
static Vector3 Vector3Add(Vector3 v1, Vector3 v2)
{
    Vector3 result = { v1.x + v2.x, v1.y + v2.y, v1.z + v2.z };

    return result;
}

// Add vector and float value
static Vector3 Vector3AddValue(Vector3 v, float add)
{
    Vector3 result = { v.x + add, v.y + add, v.z + add };

    return result;
}

// Subtract two vectors
static Vector3 Vector3Subtract(Vector3 v1, Vector3 v2)
{
    Vector3 result = { v1.x - v2.x, v1.y - v2.y, v1.z - v2.z };

    return result;
}

// Subtract vector by float value
static Vector3 Vector3SubtractValue(Vector3 v, float sub)
{
    Vector3 result = { v.x - sub, v.y - sub, v.z - sub };

    return result;
}

// Multiply vector by scalar
static Vector3 Vector3Scale(Vector3 v, float scalar)
{
    Vector3 result = { v.x*scalar, v.y*scalar, v.z*scalar };

    return result;
}

// Multiply vector by vector
static Vector3 Vector3Multiply(Vector3 v1, Vector3 v2)
{
    Vector3 result = { v1.x*v2.x, v1.y*v2.y, v1.z*v2.z };

    return result;
}

// Calculate two vectors cross product
static Vector3 Vector3CrossProduct(Vector3 v1, Vector3 v2)
{
    Vector3 result = { v1.y*v2.z - v1.z*v2.y, v1.z*v2.x - v1.x*v2.z, v1.x*v2.y - v1.y*v2.x };

    return result;
}

// Calculate one vector perpendicular vector
static Vector3 Vector3Perpendicular(Vector3 v)
{
    Vector3 result = { 0 };

    float min = cast(float) fabs(v.x);
    Vector3 cardinalAxis = {1.0f, 0.0f, 0.0f};

    if (fabs(v.y) < min)
    {
        min = cast(float) fabs(v.y);
        Vector3 tmp = {0.0f, 1.0f, 0.0f};
        cardinalAxis = tmp;
    }

    if (fabs(v.z) < min)
    {
        Vector3 tmp = {0.0f, 0.0f, 1.0f};
        cardinalAxis = tmp;
    }

    // Cross product between vectors
    result.x = v.y*cardinalAxis.z - v.z*cardinalAxis.y;
    result.y = v.z*cardinalAxis.x - v.x*cardinalAxis.z;
    result.z = v.x*cardinalAxis.y - v.y*cardinalAxis.x;

    return result;
}

// Calculate vector length
static float Vector3Length(const Vector3 v)
{
    float result = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);

    return result;
}

// Calculate vector square length
static float Vector3LengthSqr(const Vector3 v)
{
    float result = v.x*v.x + v.y*v.y + v.z*v.z;

    return result;
}

// Calculate two vectors dot product
static float Vector3DotProduct(Vector3 v1, Vector3 v2)
{
    float result = (v1.x*v2.x + v1.y*v2.y + v1.z*v2.z);

    return result;
}

// Calculate distance between two vectors
static float Vector3Distance(Vector3 v1, Vector3 v2)
{
    float result = 0.0f;

    float dx = v2.x - v1.x;
    float dy = v2.y - v1.y;
    float dz = v2.z - v1.z;
    result = sqrtf(dx*dx + dy*dy + dz*dz);

    return result;
}

// Calculate angle between two vectors in XY and XZ
static Vector2 Vector3Angle(Vector3 v1, Vector3 v2)
{
    Vector2 result = { 0 };

    float dx = v2.x - v1.x;
    float dy = v2.y - v1.y;
    float dz = v2.z - v1.z;

    result.x = atan2f(dx, dz);                      // Angle in XZ
    result.y = atan2f(dy, sqrtf(dx*dx + dz*dz));    // Angle in XY

    return result;
}

// Negate provided vector (invert direction)
static Vector3 Vector3Negate(Vector3 v)
{
    Vector3 result = { -v.x, -v.y, -v.z };

    return result;
}

// Divide vector by vector
static Vector3 Vector3Divide(Vector3 v1, Vector3 v2)
{
    Vector3 result = { v1.x/v2.x, v1.y/v2.y, v1.z/v2.z };

    return result;
}

// Normalize provided vector
static Vector3 Vector3Normalize(Vector3 v)
{
    Vector3 result = v;

    float length = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);
    if (length == 0.0f) length = 1.0f;
    float ilength = 1.0f/length;

    result.x *= ilength;
    result.y *= ilength;
    result.z *= ilength;

    return result;
}

// Orthonormalize provided vectors
// Makes vectors normalized and orthogonal to each other
// Gram-Schmidt function implementation
static void Vector3OrthoNormalize(Vector3 *v1, Vector3 *v2)
{
    float length = 0.0f;
    float ilength = 0.0f;

    // Vector3Normalize(*v1);
    Vector3 v = *v1;
    length = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);
    if (length == 0.0f) length = 1.0f;
    ilength = 1.0f/length;
    v1.x *= ilength;
    v1.y *= ilength;
    v1.z *= ilength;

    // Vector3CrossProduct(*v1, *v2)
    Vector3 vn1 = { v1.y*v2.z - v1.z*v2.y, v1.z*v2.x - v1.x*v2.z, v1.x*v2.y - v1.y*v2.x };

    // Vector3Normalize(vn1);
    v = vn1;
    length = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);
    if (length == 0.0f) length = 1.0f;
    ilength = 1.0f/length;
    vn1.x *= ilength;
    vn1.y *= ilength;
    vn1.z *= ilength;

    // Vector3CrossProduct(vn1, *v1)
    Vector3 vn2 = { vn1.y*v1.z - vn1.z*v1.y, vn1.z*v1.x - vn1.x*v1.z, vn1.x*v1.y - vn1.y*v1.x };

    *v2 = vn2;
}

// Transforms a Vector3 by a given Matrix
static Vector3 Vector3Transform(Vector3 v, Matrix mat)
{
    Vector3 result = { 0 };

    float x = v.x;
    float y = v.y;
    float z = v.z;

    result.x = mat.m0*x + mat.m4*y + mat.m8*z + mat.m12;
    result.y = mat.m1*x + mat.m5*y + mat.m9*z + mat.m13;
    result.z = mat.m2*x + mat.m6*y + mat.m10*z + mat.m14;

    return result;
}

// Transform a vector by quaternion rotation
static Vector3 Vector3RotateByQuaternion(Vector3 v, Quaternion q)
{
    Vector3 result = { 0 };

    result.x = v.x*(q.x*q.x + q.w*q.w - q.y*q.y - q.z*q.z) + v.y*(2*q.x*q.y - 2*q.w*q.z) + v.z*(2*q.x*q.z + 2*q.w*q.y);
    result.y = v.x*(2*q.w*q.z + 2*q.x*q.y) + v.y*(q.w*q.w - q.x*q.x + q.y*q.y - q.z*q.z) + v.z*(-2*q.w*q.x + 2*q.y*q.z);
    result.z = v.x*(-2*q.w*q.y + 2*q.x*q.z) + v.y*(2*q.w*q.x + 2*q.y*q.z)+ v.z*(q.w*q.w - q.x*q.x - q.y*q.y + q.z*q.z);

    return result;
}

// Calculate linear interpolation between two vectors
static Vector3 Vector3Lerp(Vector3 v1, Vector3 v2, float amount)
{
    Vector3 result = { 0 };

    result.x = v1.x + amount*(v2.x - v1.x);
    result.y = v1.y + amount*(v2.y - v1.y);
    result.z = v1.z + amount*(v2.z - v1.z);

    return result;
}

// Calculate reflected vector to normal
static Vector3 Vector3Reflect(Vector3 v, Vector3 normal)
{
    Vector3 result = { 0 };

    // I is the original vector
    // N is the normal of the incident plane
    // R = I - (2*N*(DotProduct[I, N]))

    float dotProduct = (v.x*normal.x + v.y*normal.y + v.z*normal.z);

    result.x = v.x - (2.0f*normal.x)*dotProduct;
    result.y = v.y - (2.0f*normal.y)*dotProduct;
    result.z = v.z - (2.0f*normal.z)*dotProduct;

    return result;
}

// Get min value for each pair of components
static Vector3 Vector3Min(Vector3 v1, Vector3 v2)
{
    Vector3 result = { 0 };

    result.x = fminf(v1.x, v2.x);
    result.y = fminf(v1.y, v2.y);
    result.z = fminf(v1.z, v2.z);

    return result;
}

// Get max value for each pair of components
static Vector3 Vector3Max(Vector3 v1, Vector3 v2)
{
    Vector3 result = { 0 };

    result.x = fmaxf(v1.x, v2.x);
    result.y = fmaxf(v1.y, v2.y);
    result.z = fmaxf(v1.z, v2.z);

    return result;
}

// Compute barycenter coordinates (u, v, w) for point p with respect to triangle (a, b, c)
// NOTE: Assumes P is on the plane of the triangle
static Vector3 Vector3Barycenter(Vector3 p, Vector3 a, Vector3 b, Vector3 c)
{
    Vector3 result = { 0 };

    Vector3 v0 = { b.x - a.x, b.y - a.y, b.z - a.z };   // Vector3Subtract(b, a)
    Vector3 v1 = { c.x - a.x, c.y - a.y, c.z - a.z };   // Vector3Subtract(c, a)
    Vector3 v2 = { p.x - a.x, p.y - a.y, p.z - a.z };   // Vector3Subtract(p, a)
    float d00 = (v0.x*v0.x + v0.y*v0.y + v0.z*v0.z);    // Vector3DotProduct(v0, v0)
    float d01 = (v0.x*v1.x + v0.y*v1.y + v0.z*v1.z);    // Vector3DotProduct(v0, v1)
    float d11 = (v1.x*v1.x + v1.y*v1.y + v1.z*v1.z);    // Vector3DotProduct(v1, v1)
    float d20 = (v2.x*v0.x + v2.y*v0.y + v2.z*v0.z);    // Vector3DotProduct(v2, v0)
    float d21 = (v2.x*v1.x + v2.y*v1.y + v2.z*v1.z);    // Vector3DotProduct(v2, v1)

    float denom = d00*d11 - d01*d01;

    result.y = (d11*d20 - d01*d21)/denom;
    result.z = (d00*d21 - d01*d20)/denom;
    result.x = 1.0f - (result.z + result.y);

    return result;
}

// Projects a Vector3 from screen space into object space
// NOTE: We are avoiding calling other raymath functions despite available
static Vector3 Vector3Unproject(Vector3 source, Matrix projection, Matrix view)
{
    Vector3 result = { 0 };

    // Calculate unproject matrix (multiply view patrix by projection matrix) and invert it
    Matrix matViewProj = {      // MatrixMultiply(view, projection);
        view.m0*projection.m0 + view.m1*projection.m4 + view.m2*projection.m8 + view.m3*projection.m12,
        view.m0*projection.m1 + view.m1*projection.m5 + view.m2*projection.m9 + view.m3*projection.m13,
        view.m0*projection.m2 + view.m1*projection.m6 + view.m2*projection.m10 + view.m3*projection.m14,
        view.m0*projection.m3 + view.m1*projection.m7 + view.m2*projection.m11 + view.m3*projection.m15,
        view.m4*projection.m0 + view.m5*projection.m4 + view.m6*projection.m8 + view.m7*projection.m12,
        view.m4*projection.m1 + view.m5*projection.m5 + view.m6*projection.m9 + view.m7*projection.m13,
        view.m4*projection.m2 + view.m5*projection.m6 + view.m6*projection.m10 + view.m7*projection.m14,
        view.m4*projection.m3 + view.m5*projection.m7 + view.m6*projection.m11 + view.m7*projection.m15,
        view.m8*projection.m0 + view.m9*projection.m4 + view.m10*projection.m8 + view.m11*projection.m12,
        view.m8*projection.m1 + view.m9*projection.m5 + view.m10*projection.m9 + view.m11*projection.m13,
        view.m8*projection.m2 + view.m9*projection.m6 + view.m10*projection.m10 + view.m11*projection.m14,
        view.m8*projection.m3 + view.m9*projection.m7 + view.m10*projection.m11 + view.m11*projection.m15,
        view.m12*projection.m0 + view.m13*projection.m4 + view.m14*projection.m8 + view.m15*projection.m12,
        view.m12*projection.m1 + view.m13*projection.m5 + view.m14*projection.m9 + view.m15*projection.m13,
        view.m12*projection.m2 + view.m13*projection.m6 + view.m14*projection.m10 + view.m15*projection.m14,
        view.m12*projection.m3 + view.m13*projection.m7 + view.m14*projection.m11 + view.m15*projection.m15 };

    // Calculate inverted matrix . MatrixInvert(matViewProj);
    // Cache the matrix values (speed optimization)
    float a00 = matViewProj.m0, a01 = matViewProj.m1, a02 = matViewProj.m2, a03 = matViewProj.m3;
    float a10 = matViewProj.m4, a11 = matViewProj.m5, a12 = matViewProj.m6, a13 = matViewProj.m7;
    float a20 = matViewProj.m8, a21 = matViewProj.m9, a22 = matViewProj.m10, a23 = matViewProj.m11;
    float a30 = matViewProj.m12, a31 = matViewProj.m13, a32 = matViewProj.m14, a33 = matViewProj.m15;

    float b00 = a00*a11 - a01*a10;
    float b01 = a00*a12 - a02*a10;
    float b02 = a00*a13 - a03*a10;
    float b03 = a01*a12 - a02*a11;
    float b04 = a01*a13 - a03*a11;
    float b05 = a02*a13 - a03*a12;
    float b06 = a20*a31 - a21*a30;
    float b07 = a20*a32 - a22*a30;
    float b08 = a20*a33 - a23*a30;
    float b09 = a21*a32 - a22*a31;
    float b10 = a21*a33 - a23*a31;
    float b11 = a22*a33 - a23*a32;

    // Calculate the invert determinant (inlined to avoid double-caching)
    float invDet = 1.0f/(b00*b11 - b01*b10 + b02*b09 + b03*b08 - b04*b07 + b05*b06);

    Matrix matViewProjInv = {
        (a11*b11 - a12*b10 + a13*b09)*invDet,
        (-a01*b11 + a02*b10 - a03*b09)*invDet,
        (a31*b05 - a32*b04 + a33*b03)*invDet,
        (-a21*b05 + a22*b04 - a23*b03)*invDet,
        (-a10*b11 + a12*b08 - a13*b07)*invDet,
        (a00*b11 - a02*b08 + a03*b07)*invDet,
        (-a30*b05 + a32*b02 - a33*b01)*invDet,
        (a20*b05 - a22*b02 + a23*b01)*invDet,
        (a10*b10 - a11*b08 + a13*b06)*invDet,
        (-a00*b10 + a01*b08 - a03*b06)*invDet,
        (a30*b04 - a31*b02 + a33*b00)*invDet,
        (-a20*b04 + a21*b02 - a23*b00)*invDet,
        (-a10*b09 + a11*b07 - a12*b06)*invDet,
        (a00*b09 - a01*b07 + a02*b06)*invDet,
        (-a30*b03 + a31*b01 - a32*b00)*invDet,
        (a20*b03 - a21*b01 + a22*b00)*invDet };

    // Create quaternion from source point
    Quaternion quat = { source.x, source.y, source.z, 1.0f };

    // Multiply quat point by unproject matrix
    Quaternion qtransformed = {     // QuaternionTransform(quat, matViewProjInv)
        matViewProjInv.m0*quat.x + matViewProjInv.m4*quat.y + matViewProjInv.m8*quat.z + matViewProjInv.m12*quat.w,
        matViewProjInv.m1*quat.x + matViewProjInv.m5*quat.y + matViewProjInv.m9*quat.z + matViewProjInv.m13*quat.w,
        matViewProjInv.m2*quat.x + matViewProjInv.m6*quat.y + matViewProjInv.m10*quat.z + matViewProjInv.m14*quat.w,
        matViewProjInv.m3*quat.x + matViewProjInv.m7*quat.y + matViewProjInv.m11*quat.z + matViewProjInv.m15*quat.w };

    // Normalized world points in vectors
    result.x = qtransformed.x/qtransformed.w;
    result.y = qtransformed.y/qtransformed.w;
    result.z = qtransformed.z/qtransformed.w;

    return result;
}

// Get Vector3 as float array
static float3 Vector3ToFloatV(Vector3 v)
{
    float3 buffer = { 0 };

    buffer.v[0] = v.x;
    buffer.v[1] = v.y;
    buffer.v[2] = v.z;

    return buffer;
}

//----------------------------------------------------------------------------------
// Module Functions Definition - Matrix math
//----------------------------------------------------------------------------------

// Compute matrix determinant
static float MatrixDeterminant(Matrix mat)
{
    float result = 0.0f;

    // Cache the matrix values (speed optimization)
    float a00 = mat.m0, a01 = mat.m1, a02 = mat.m2, a03 = mat.m3;
    float a10 = mat.m4, a11 = mat.m5, a12 = mat.m6, a13 = mat.m7;
    float a20 = mat.m8, a21 = mat.m9, a22 = mat.m10, a23 = mat.m11;
    float a30 = mat.m12, a31 = mat.m13, a32 = mat.m14, a33 = mat.m15;

    result = a30*a21*a12*a03 - a20*a31*a12*a03 - a30*a11*a22*a03 + a10*a31*a22*a03 +
             a20*a11*a32*a03 - a10*a21*a32*a03 - a30*a21*a02*a13 + a20*a31*a02*a13 +
             a30*a01*a22*a13 - a00*a31*a22*a13 - a20*a01*a32*a13 + a00*a21*a32*a13 +
             a30*a11*a02*a23 - a10*a31*a02*a23 - a30*a01*a12*a23 + a00*a31*a12*a23 +
             a10*a01*a32*a23 - a00*a11*a32*a23 - a20*a11*a02*a33 + a10*a21*a02*a33 +
             a20*a01*a12*a33 - a00*a21*a12*a33 - a10*a01*a22*a33 + a00*a11*a22*a33;

    return result;
}

// Get the trace of the matrix (sum of the values along the diagonal)
static float MatrixTrace(Matrix mat)
{
    float result = (mat.m0 + mat.m5 + mat.m10 + mat.m15);

    return result;
}

// Transposes provided matrix
static Matrix MatrixTranspose(Matrix mat)
{
    Matrix result = { 0 };

    result.m0 = mat.m0;
    result.m1 = mat.m4;
    result.m2 = mat.m8;
    result.m3 = mat.m12;
    result.m4 = mat.m1;
    result.m5 = mat.m5;
    result.m6 = mat.m9;
    result.m7 = mat.m13;
    result.m8 = mat.m2;
    result.m9 = mat.m6;
    result.m10 = mat.m10;
    result.m11 = mat.m14;
    result.m12 = mat.m3;
    result.m13 = mat.m7;
    result.m14 = mat.m11;
    result.m15 = mat.m15;

    return result;
}

// Invert provided matrix
static Matrix MatrixInvert(Matrix mat)
{
    Matrix result = { 0 };

    // Cache the matrix values (speed optimization)
    float a00 = mat.m0, a01 = mat.m1, a02 = mat.m2, a03 = mat.m3;
    float a10 = mat.m4, a11 = mat.m5, a12 = mat.m6, a13 = mat.m7;
    float a20 = mat.m8, a21 = mat.m9, a22 = mat.m10, a23 = mat.m11;
    float a30 = mat.m12, a31 = mat.m13, a32 = mat.m14, a33 = mat.m15;

    float b00 = a00*a11 - a01*a10;
    float b01 = a00*a12 - a02*a10;
    float b02 = a00*a13 - a03*a10;
    float b03 = a01*a12 - a02*a11;
    float b04 = a01*a13 - a03*a11;
    float b05 = a02*a13 - a03*a12;
    float b06 = a20*a31 - a21*a30;
    float b07 = a20*a32 - a22*a30;
    float b08 = a20*a33 - a23*a30;
    float b09 = a21*a32 - a22*a31;
    float b10 = a21*a33 - a23*a31;
    float b11 = a22*a33 - a23*a32;

    // Calculate the invert determinant (inlined to avoid double-caching)
    float invDet = 1.0f/(b00*b11 - b01*b10 + b02*b09 + b03*b08 - b04*b07 + b05*b06);

    result.m0 = (a11*b11 - a12*b10 + a13*b09)*invDet;
    result.m1 = (-a01*b11 + a02*b10 - a03*b09)*invDet;
    result.m2 = (a31*b05 - a32*b04 + a33*b03)*invDet;
    result.m3 = (-a21*b05 + a22*b04 - a23*b03)*invDet;
    result.m4 = (-a10*b11 + a12*b08 - a13*b07)*invDet;
    result.m5 = (a00*b11 - a02*b08 + a03*b07)*invDet;
    result.m6 = (-a30*b05 + a32*b02 - a33*b01)*invDet;
    result.m7 = (a20*b05 - a22*b02 + a23*b01)*invDet;
    result.m8 = (a10*b10 - a11*b08 + a13*b06)*invDet;
    result.m9 = (-a00*b10 + a01*b08 - a03*b06)*invDet;
    result.m10 = (a30*b04 - a31*b02 + a33*b00)*invDet;
    result.m11 = (-a20*b04 + a21*b02 - a23*b00)*invDet;
    result.m12 = (-a10*b09 + a11*b07 - a12*b06)*invDet;
    result.m13 = (a00*b09 - a01*b07 + a02*b06)*invDet;
    result.m14 = (-a30*b03 + a31*b01 - a32*b00)*invDet;
    result.m15 = (a20*b03 - a21*b01 + a22*b00)*invDet;

    return result;
}

// Normalize provided matrix
static Matrix MatrixNormalize(Matrix mat)
{
    Matrix result = { 0 };

    // Cache the matrix values (speed optimization)
    float a00 = mat.m0, a01 = mat.m1, a02 = mat.m2, a03 = mat.m3;
    float a10 = mat.m4, a11 = mat.m5, a12 = mat.m6, a13 = mat.m7;
    float a20 = mat.m8, a21 = mat.m9, a22 = mat.m10, a23 = mat.m11;
    float a30 = mat.m12, a31 = mat.m13, a32 = mat.m14, a33 = mat.m15;

    // MatrixDeterminant(mat)
    float det = a30*a21*a12*a03 - a20*a31*a12*a03 - a30*a11*a22*a03 + a10*a31*a22*a03 +
                a20*a11*a32*a03 - a10*a21*a32*a03 - a30*a21*a02*a13 + a20*a31*a02*a13 +
                a30*a01*a22*a13 - a00*a31*a22*a13 - a20*a01*a32*a13 + a00*a21*a32*a13 +
                a30*a11*a02*a23 - a10*a31*a02*a23 - a30*a01*a12*a23 + a00*a31*a12*a23 +
                a10*a01*a32*a23 - a00*a11*a32*a23 - a20*a11*a02*a33 + a10*a21*a02*a33 +
                a20*a01*a12*a33 - a00*a21*a12*a33 - a10*a01*a22*a33 + a00*a11*a22*a33;

    result.m0 = mat.m0/det;
    result.m1 = mat.m1/det;
    result.m2 = mat.m2/det;
    result.m3 = mat.m3/det;
    result.m4 = mat.m4/det;
    result.m5 = mat.m5/det;
    result.m6 = mat.m6/det;
    result.m7 = mat.m7/det;
    result.m8 = mat.m8/det;
    result.m9 = mat.m9/det;
    result.m10 = mat.m10/det;
    result.m11 = mat.m11/det;
    result.m12 = mat.m12/det;
    result.m13 = mat.m13/det;
    result.m14 = mat.m14/det;
    result.m15 = mat.m15/det;

    return result;
}

// Get identity matrix
static Matrix MatrixIdentity()
{
    Matrix result = { 1.0f, 0.0f, 0.0f, 0.0f,
                      0.0f, 1.0f, 0.0f, 0.0f,
                      0.0f, 0.0f, 1.0f, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f };

    return result;
}

// Add two matrices
static Matrix MatrixAdd(Matrix left, Matrix right)
{
    Matrix result = { 0 };

    result.m0 = left.m0 + right.m0;
    result.m1 = left.m1 + right.m1;
    result.m2 = left.m2 + right.m2;
    result.m3 = left.m3 + right.m3;
    result.m4 = left.m4 + right.m4;
    result.m5 = left.m5 + right.m5;
    result.m6 = left.m6 + right.m6;
    result.m7 = left.m7 + right.m7;
    result.m8 = left.m8 + right.m8;
    result.m9 = left.m9 + right.m9;
    result.m10 = left.m10 + right.m10;
    result.m11 = left.m11 + right.m11;
    result.m12 = left.m12 + right.m12;
    result.m13 = left.m13 + right.m13;
    result.m14 = left.m14 + right.m14;
    result.m15 = left.m15 + right.m15;

    return result;
}

// Subtract two matrices (left - right)
static Matrix MatrixSubtract(Matrix left, Matrix right)
{
    Matrix result = { 0 };

    result.m0 = left.m0 - right.m0;
    result.m1 = left.m1 - right.m1;
    result.m2 = left.m2 - right.m2;
    result.m3 = left.m3 - right.m3;
    result.m4 = left.m4 - right.m4;
    result.m5 = left.m5 - right.m5;
    result.m6 = left.m6 - right.m6;
    result.m7 = left.m7 - right.m7;
    result.m8 = left.m8 - right.m8;
    result.m9 = left.m9 - right.m9;
    result.m10 = left.m10 - right.m10;
    result.m11 = left.m11 - right.m11;
    result.m12 = left.m12 - right.m12;
    result.m13 = left.m13 - right.m13;
    result.m14 = left.m14 - right.m14;
    result.m15 = left.m15 - right.m15;

    return result;
}

// Get two matrix multiplication
// NOTE: When multiplying matrices... the order matters!
static Matrix MatrixMultiply(Matrix left, Matrix right)
{
    Matrix result = { 0 };

    result.m0 = left.m0*right.m0 + left.m1*right.m4 + left.m2*right.m8 + left.m3*right.m12;
    result.m1 = left.m0*right.m1 + left.m1*right.m5 + left.m2*right.m9 + left.m3*right.m13;
    result.m2 = left.m0*right.m2 + left.m1*right.m6 + left.m2*right.m10 + left.m3*right.m14;
    result.m3 = left.m0*right.m3 + left.m1*right.m7 + left.m2*right.m11 + left.m3*right.m15;
    result.m4 = left.m4*right.m0 + left.m5*right.m4 + left.m6*right.m8 + left.m7*right.m12;
    result.m5 = left.m4*right.m1 + left.m5*right.m5 + left.m6*right.m9 + left.m7*right.m13;
    result.m6 = left.m4*right.m2 + left.m5*right.m6 + left.m6*right.m10 + left.m7*right.m14;
    result.m7 = left.m4*right.m3 + left.m5*right.m7 + left.m6*right.m11 + left.m7*right.m15;
    result.m8 = left.m8*right.m0 + left.m9*right.m4 + left.m10*right.m8 + left.m11*right.m12;
    result.m9 = left.m8*right.m1 + left.m9*right.m5 + left.m10*right.m9 + left.m11*right.m13;
    result.m10 = left.m8*right.m2 + left.m9*right.m6 + left.m10*right.m10 + left.m11*right.m14;
    result.m11 = left.m8*right.m3 + left.m9*right.m7 + left.m10*right.m11 + left.m11*right.m15;
    result.m12 = left.m12*right.m0 + left.m13*right.m4 + left.m14*right.m8 + left.m15*right.m12;
    result.m13 = left.m12*right.m1 + left.m13*right.m5 + left.m14*right.m9 + left.m15*right.m13;
    result.m14 = left.m12*right.m2 + left.m13*right.m6 + left.m14*right.m10 + left.m15*right.m14;
    result.m15 = left.m12*right.m3 + left.m13*right.m7 + left.m14*right.m11 + left.m15*right.m15;

    return result;
}

// Get translation matrix
static Matrix MatrixTranslate(float x, float y, float z)
{
    Matrix result = { 1.0f, 0.0f, 0.0f, x,
                      0.0f, 1.0f, 0.0f, y,
                      0.0f, 0.0f, 1.0f, z,
                      0.0f, 0.0f, 0.0f, 1.0f };

    return result;
}

// Create rotation matrix from axis and angle
// NOTE: Angle should be provided in radians
static Matrix MatrixRotate(Vector3 axis, float angle)
{
    Matrix result = { 0 };

    float x = axis.x, y = axis.y, z = axis.z;

    float lengthSquared = x*x + y*y + z*z;

    if ((lengthSquared != 1.0f) && (lengthSquared != 0.0f))
    {
        float ilength = 1.0f/sqrtf(lengthSquared);
        x *= ilength;
        y *= ilength;
        z *= ilength;
    }

    float sinres = sinf(angle);
    float cosres = cosf(angle);
    float t = 1.0f - cosres;

    result.m0 = x*x*t + cosres;
    result.m1 = y*x*t + z*sinres;
    result.m2 = z*x*t - y*sinres;
    result.m3 = 0.0f;

    result.m4 = x*y*t - z*sinres;
    result.m5 = y*y*t + cosres;
    result.m6 = z*y*t + x*sinres;
    result.m7 = 0.0f;

    result.m8 = x*z*t + y*sinres;
    result.m9 = y*z*t - x*sinres;
    result.m10 = z*z*t + cosres;
    result.m11 = 0.0f;

    result.m12 = 0.0f;
    result.m13 = 0.0f;
    result.m14 = 0.0f;
    result.m15 = 1.0f;

    return result;
}

// Get x-rotation matrix (angle in radians)
static Matrix MatrixRotateX(float angle)
{
    Matrix result = { 1.0f, 0.0f, 0.0f, 0.0f,
                      0.0f, 1.0f, 0.0f, 0.0f,
                      0.0f, 0.0f, 1.0f, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f }; // MatrixIdentity()

    float cosres = cosf(angle);
    float sinres = sinf(angle);

    result.m5 = cosres;
    result.m6 = -sinres;
    result.m9 = sinres;
    result.m10 = cosres;

    return result;
}

// Get y-rotation matrix (angle in radians)
static Matrix MatrixRotateY(float angle)
{
    Matrix result = { 1.0f, 0.0f, 0.0f, 0.0f,
                      0.0f, 1.0f, 0.0f, 0.0f,
                      0.0f, 0.0f, 1.0f, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f }; // MatrixIdentity()

    float cosres = cosf(angle);
    float sinres = sinf(angle);

    result.m0 = cosres;
    result.m2 = sinres;
    result.m8 = -sinres;
    result.m10 = cosres;

    return result;
}

// Get z-rotation matrix (angle in radians)
static Matrix MatrixRotateZ(float angle)
{
    Matrix result = { 1.0f, 0.0f, 0.0f, 0.0f,
                      0.0f, 1.0f, 0.0f, 0.0f,
                      0.0f, 0.0f, 1.0f, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f }; // MatrixIdentity()

    float cosres = cosf(angle);
    float sinres = sinf(angle);

    result.m0 = cosres;
    result.m1 = -sinres;
    result.m4 = sinres;
    result.m5 = cosres;

    return result;
}


// Get xyz-rotation matrix (angles in radians)
static Matrix MatrixRotateXYZ(Vector3 ang)
{
    Matrix result = { 1.0f, 0.0f, 0.0f, 0.0f,
                      0.0f, 1.0f, 0.0f, 0.0f,
                      0.0f, 0.0f, 1.0f, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f }; // MatrixIdentity()

    float cosz = cosf(-ang.z);
    float sinz = sinf(-ang.z);
    float cosy = cosf(-ang.y);
    float siny = sinf(-ang.y);
    float cosx = cosf(-ang.x);
    float sinx = sinf(-ang.x);

    result.m0 = cosz*cosy;
    result.m4 = (cosz*siny*sinx) - (sinz*cosx);
    result.m8 = (cosz*siny*cosx) + (sinz*sinx);

    result.m1 = sinz*cosy;
    result.m5 = (sinz*siny*sinx) + (cosz*cosx);
    result.m9 = (sinz*siny*cosx) - (cosz*sinx);

    result.m2 = -siny;
    result.m6 = cosy*sinx;
    result.m10= cosy*cosx;

    return result;
}

// Get zyx-rotation matrix (angles in radians)
static Matrix MatrixRotateZYX(Vector3 ang)
{
    Matrix result = { 0 };

    float cz = cosf(ang.z);
    float sz = sinf(ang.z);
    float cy = cosf(ang.y);
    float sy = sinf(ang.y);
    float cx = cosf(ang.x);
    float sx = sinf(ang.x);

    result.m0 = cz*cy;
    result.m1 = cz*sy*sx - cx*sz;
    result.m2 = sz*sx + cz*cx*sy;
    result.m3 = 0;

    result.m4 = cy*sz;
    result.m5 = cz*cx + sz*sy*sx;
    result.m6 = cx*sz*sy - cz*sx;
    result.m7 = 0;

    result.m8 = -sy;
    result.m9 = cy*sx;
    result.m10 = cy*cx;
    result.m11 = 0;

    result.m12 = 0;
    result.m13 = 0;
    result.m14 = 0;
    result.m15 = 1;

    return result;
}

// Get scaling matrix
static Matrix MatrixScale(float x, float y, float z)
{
    Matrix result = { x, 0.0f, 0.0f, 0.0f,
                      0.0f, y, 0.0f, 0.0f,
                      0.0f, 0.0f, z, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f };

    return result;
}

// Get perspective projection matrix
static Matrix MatrixFrustum(double left, double right, double bottom, double top, double near, double far)
{
    Matrix result = { 0 };

    float rl = cast(float)(right - left);
    float tb = cast(float)(top - bottom);
    float fn = cast(float)(far - near);

    result.m0 = (cast(float)near*2.0f)/rl;
    result.m1 = 0.0f;
    result.m2 = 0.0f;
    result.m3 = 0.0f;

    result.m4 = 0.0f;
    result.m5 = (cast(float)near*2.0f)/tb;
    result.m6 = 0.0f;
    result.m7 = 0.0f;

    result.m8 = (cast(float)right + cast(float)left)/rl;
    result.m9 = (cast(float)top + cast(float)bottom)/tb;
    result.m10 = -(cast(float)far + cast(float)near)/fn;
    result.m11 = -1.0f;

    result.m12 = 0.0f;
    result.m13 = 0.0f;
    result.m14 = -(cast(float)far*cast(float)near*2.0f)/fn;
    result.m15 = 0.0f;

    return result;
}

// Get perspective projection matrix
// NOTE: Angle should be provided in radians
static Matrix MatrixPerspective(double fovy, double aspect, double near, double far)
{
    Matrix result = { 0 };

    double top = near*tan(fovy*0.5);
    double bottom = -top;
    double right = top*aspect;
    double left = -right;

    // MatrixFrustum(-right, right, -top, top, near, far);
    float rl = cast(float)(right - left);
    float tb = cast(float)(top - bottom);
    float fn = cast(float)(far - near);

    result.m0 = (cast(float)near*2.0f)/rl;
    result.m5 = (cast(float)near*2.0f)/tb;
    result.m8 = (cast(float)right + cast(float)left)/rl;
    result.m9 = (cast(float)top + cast(float)bottom)/tb;
    result.m10 = -(cast(float)far + cast(float)near)/fn;
    result.m11 = -1.0f;
    result.m14 = -(cast(float)far*cast(float)near*2.0f)/fn;

    return result;
}

// Get orthographic projection matrix
static Matrix MatrixOrtho(double left, double right, double bottom, double top, double near, double far)
{
    Matrix result = { 0 };

    float rl = cast(float)(right - left);
    float tb = cast(float)(top - bottom);
    float fn = cast(float)(far - near);

    result.m0 = 2.0f/rl;
    result.m1 = 0.0f;
    result.m2 = 0.0f;
    result.m3 = 0.0f;
    result.m4 = 0.0f;
    result.m5 = 2.0f/tb;
    result.m6 = 0.0f;
    result.m7 = 0.0f;
    result.m8 = 0.0f;
    result.m9 = 0.0f;
    result.m10 = -2.0f/fn;
    result.m11 = 0.0f;
    result.m12 = -(cast(float)left + cast(float)right)/rl;
    result.m13 = -(cast(float)top + cast(float)bottom)/tb;
    result.m14 = -(cast(float)far + cast(float)near)/fn;
    result.m15 = 1.0f;

    return result;
}

// Get camera look-at matrix (view matrix)
static Matrix MatrixLookAt(Vector3 eye, Vector3 target, Vector3 up)
{
    Matrix result = { 0 };

    float length = 0.0f;
    float ilength = 0.0f;

    // Vector3Subtract(eye, target)
    Vector3 vz = { eye.x - target.x, eye.y - target.y, eye.z - target.z };

    // Vector3Normalize(vz)
    Vector3 v = vz;
    length = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);
    if (length == 0.0f) length = 1.0f;
    ilength = 1.0f/length;
    vz.x *= ilength;
    vz.y *= ilength;
    vz.z *= ilength;

    // Vector3CrossProduct(up, vz)
    Vector3 vx = { up.y*vz.z - up.z*vz.y, up.z*vz.x - up.x*vz.z, up.x*vz.y - up.y*vz.x };

    // Vector3Normalize(x)
    v = vx;
    length = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);
    if (length == 0.0f) length = 1.0f;
    ilength = 1.0f/length;
    vx.x *= ilength;
    vx.y *= ilength;
    vx.z *= ilength;

    // Vector3CrossProduct(vz, vx)
    Vector3 vy = { vz.y*vx.z - vz.z*vx.y, vz.z*vx.x - vz.x*vx.z, vz.x*vx.y - vz.y*vx.x };

    result.m0 = vx.x;
    result.m1 = vy.x;
    result.m2 = vz.x;
    result.m3 = 0.0f;
    result.m4 = vx.y;
    result.m5 = vy.y;
    result.m6 = vz.y;
    result.m7 = 0.0f;
    result.m8 = vx.z;
    result.m9 = vy.z;
    result.m10 = vz.z;
    result.m11 = 0.0f;
    result.m12 = -(vx.x*eye.x + vx.y*eye.y + vx.z*eye.z);   // Vector3DotProduct(vx, eye)
    result.m13 = -(vy.x*eye.x + vy.y*eye.y + vy.z*eye.z);   // Vector3DotProduct(vy, eye)
    result.m14 = -(vz.x*eye.x + vz.y*eye.y + vz.z*eye.z);   // Vector3DotProduct(vz, eye)
    result.m15 = 1.0f;

    return result;
}

// Get float array of matrix data
static float16 MatrixToFloatV(Matrix mat)
{
    float16 result = { 0 };

    result.v[0] = mat.m0;
    result.v[1] = mat.m1;
    result.v[2] = mat.m2;
    result.v[3] = mat.m3;
    result.v[4] = mat.m4;
    result.v[5] = mat.m5;
    result.v[6] = mat.m6;
    result.v[7] = mat.m7;
    result.v[8] = mat.m8;
    result.v[9] = mat.m9;
    result.v[10] = mat.m10;
    result.v[11] = mat.m11;
    result.v[12] = mat.m12;
    result.v[13] = mat.m13;
    result.v[14] = mat.m14;
    result.v[15] = mat.m15;

    return result;
}

//----------------------------------------------------------------------------------
// Module Functions Definition - Quaternion math
//----------------------------------------------------------------------------------

// Add two quaternions
static Quaternion QuaternionAdd(Quaternion q1, Quaternion q2)
{
    Quaternion result = {q1.x + q2.x, q1.y + q2.y, q1.z + q2.z, q1.w + q2.w};

    return result;
}

// Add quaternion and float value
static Quaternion QuaternionAddValue(Quaternion q, float add)
{
    Quaternion result = {q.x + add, q.y + add, q.z + add, q.w + add};

    return result;
}

// Subtract two quaternions
static Quaternion QuaternionSubtract(Quaternion q1, Quaternion q2)
{
    Quaternion result = {q1.x - q2.x, q1.y - q2.y, q1.z - q2.z, q1.w - q2.w};

    return result;
}

// Subtract quaternion and float value
static Quaternion QuaternionSubtractValue(Quaternion q, float sub)
{
    Quaternion result = {q.x - sub, q.y - sub, q.z - sub, q.w - sub};

    return result;
}

// Get identity quaternion
static Quaternion QuaternionIdentity()
{
    Quaternion result = { 0.0f, 0.0f, 0.0f, 1.0f };

    return result;
}

// Computes the length of a quaternion
static float QuaternionLength(Quaternion q)
{
    float result = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);

    return result;
}

// Normalize provided quaternion
static Quaternion QuaternionNormalize(Quaternion q)
{
    Quaternion result = { 0 };

    float length = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);
    if (length == 0.0f) length = 1.0f;
    float ilength = 1.0f/length;

    result.x = q.x*ilength;
    result.y = q.y*ilength;
    result.z = q.z*ilength;
    result.w = q.w*ilength;

    return result;
}

// Invert provided quaternion
static Quaternion QuaternionInvert(Quaternion q)
{
    Quaternion result = q;

    float length = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);
    float lengthSq = length*length;

    if (lengthSq != 0.0)
    {
        float invLength = 1.0f/lengthSq;

        result.x *= -invLength;
        result.y *= -invLength;
        result.z *= -invLength;
        result.w *= invLength;
    }

    return result;
}

// Calculate two quaternion multiplication
static Quaternion QuaternionMultiply(Quaternion q1, Quaternion q2)
{
    Quaternion result = { 0 };

    float qax = q1.x, qay = q1.y, qaz = q1.z, qaw = q1.w;
    float qbx = q2.x, qby = q2.y, qbz = q2.z, qbw = q2.w;

    result.x = qax*qbw + qaw*qbx + qay*qbz - qaz*qby;
    result.y = qay*qbw + qaw*qby + qaz*qbx - qax*qbz;
    result.z = qaz*qbw + qaw*qbz + qax*qby - qay*qbx;
    result.w = qaw*qbw - qax*qbx - qay*qby - qaz*qbz;

    return result;
}

// Scale quaternion by float value
static Quaternion QuaternionScale(Quaternion q, float mul)
{
    Quaternion result = { 0 };

    float qax = q.x, qay = q.y, qaz = q.z, qaw = q.w;

    result.x = qax*mul + qaw*mul + qay*mul - qaz*mul;
    result.y = qay*mul + qaw*mul + qaz*mul - qax*mul;
    result.z = qaz*mul + qaw*mul + qax*mul - qay*mul;
    result.w = qaw*mul - qax*mul - qay*mul - qaz*mul;

    return result;
}

// Divide two quaternions
static Quaternion QuaternionDivide(Quaternion q1, Quaternion q2)
{
    Quaternion result = { q1.x/q2.x, q1.y/q2.y, q1.z/q2.z, q1.w/q2.w };

    return result;
}

// Calculate linear interpolation between two quaternions
static Quaternion QuaternionLerp(Quaternion q1, Quaternion q2, float amount)
{
    Quaternion result = { 0 };

    result.x = q1.x + amount*(q2.x - q1.x);
    result.y = q1.y + amount*(q2.y - q1.y);
    result.z = q1.z + amount*(q2.z - q1.z);
    result.w = q1.w + amount*(q2.w - q1.w);

    return result;
}

// Calculate slerp-optimized interpolation between two quaternions
static Quaternion QuaternionNlerp(Quaternion q1, Quaternion q2, float amount)
{
    Quaternion result = { 0 };

    // QuaternionLerp(q1, q2, amount)
    result.x = q1.x + amount*(q2.x - q1.x);
    result.y = q1.y + amount*(q2.y - q1.y);
    result.z = q1.z + amount*(q2.z - q1.z);
    result.w = q1.w + amount*(q2.w - q1.w);

    // QuaternionNormalize(q);
    Quaternion q = result;
    float length = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);
    if (length == 0.0f) length = 1.0f;
    float ilength = 1.0f/length;

    result.x = q.x*ilength;
    result.y = q.y*ilength;
    result.z = q.z*ilength;
    result.w = q.w*ilength;

    return result;
}

// Calculates spherical linear interpolation between two quaternions
static Quaternion QuaternionSlerp(Quaternion q1, Quaternion q2, float amount)
{
    Quaternion result = { 0 };

    float cosHalfTheta = q1.x*q2.x + q1.y*q2.y + q1.z*q2.z + q1.w*q2.w;

    if (cosHalfTheta < 0)
    {
        q2.x = -q2.x; q2.y = -q2.y; q2.z = -q2.z; q2.w = -q2.w;
        cosHalfTheta = -cosHalfTheta;
    }

    if (fabs(cosHalfTheta) >= 1.0f) result = q1;
    else if (cosHalfTheta > 0.95f) result = QuaternionNlerp(q1, q2, amount);
    else
    {
        float halfTheta = acosf(cosHalfTheta);
        float sinHalfTheta = sqrtf(1.0f - cosHalfTheta*cosHalfTheta);

        if (fabs(sinHalfTheta) < 0.001f)
        {
            result.x = (q1.x*0.5f + q2.x*0.5f);
            result.y = (q1.y*0.5f + q2.y*0.5f);
            result.z = (q1.z*0.5f + q2.z*0.5f);
            result.w = (q1.w*0.5f + q2.w*0.5f);
        }
        else
        {
            float ratioA = sinf((1 - amount)*halfTheta)/sinHalfTheta;
            float ratioB = sinf(amount*halfTheta)/sinHalfTheta;

            result.x = (q1.x*ratioA + q2.x*ratioB);
            result.y = (q1.y*ratioA + q2.y*ratioB);
            result.z = (q1.z*ratioA + q2.z*ratioB);
            result.w = (q1.w*ratioA + q2.w*ratioB);
        }
    }

    return result;
}

// Calculate quaternion based on the rotation from one vector to another
static Quaternion QuaternionFromVector3ToVector3(Vector3 from, Vector3 to)
{
    Quaternion result = { 0 };

    float cos2Theta = (from.x*to.x + from.y*to.y + from.z*to.z);    // Vector3DotProduct(from, to)
    Vector3 cross = { from.y*to.z - from.z*to.y, from.z*to.x - from.x*to.z, from.x*to.y - from.y*to.x }; // Vector3CrossProduct(from, to)

    result.x = cross.x;
    result.y = cross.y;
    result.z = cross.z;
    result.w = 1.0f + cos2Theta;

    // QuaternionNormalize(q);
    // NOTE: Normalize to essentially nlerp the original and identity to 0.5
    Quaternion q = result;
    float length = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);
    if (length == 0.0f) length = 1.0f;
    float ilength = 1.0f/length;

    result.x = q.x*ilength;
    result.y = q.y*ilength;
    result.z = q.z*ilength;
    result.w = q.w*ilength;

    return result;
}

// Get a quaternion for a given rotation matrix
static Quaternion QuaternionFromMatrix(Matrix mat)
{
    Quaternion result = { 0 };

    if ((mat.m0 > mat.m5) && (mat.m0 > mat.m10))
    {
        float s = sqrtf(1.0f + mat.m0 - mat.m5 - mat.m10)*2;

        result.x = 0.25f*s;
        result.y = (mat.m4 + mat.m1)/s;
        result.z = (mat.m2 + mat.m8)/s;
        result.w = (mat.m9 - mat.m6)/s;
    }
    else if (mat.m5 > mat.m10)
    {
        float s = sqrtf(1.0f + mat.m5 - mat.m0 - mat.m10)*2;
        result.x = (mat.m4 + mat.m1)/s;
        result.y = 0.25f*s;
        result.z = (mat.m9 + mat.m6)/s;
        result.w = (mat.m2 - mat.m8)/s;
    }
    else
    {
        float s = sqrtf(1.0f + mat.m10 - mat.m0 - mat.m5)*2;
        result.x = (mat.m2 + mat.m8)/s;
        result.y = (mat.m9 + mat.m6)/s;
        result.z = 0.25f*s;
        result.w = (mat.m4 - mat.m1)/s;
    }

    return result;
}

// Get a matrix for a given quaternion
static Matrix QuaternionToMatrix(Quaternion q)
{
    Matrix result = { 1.0f, 0.0f, 0.0f, 0.0f,
                      0.0f, 1.0f, 0.0f, 0.0f,
                      0.0f, 0.0f, 1.0f, 0.0f,
                      0.0f, 0.0f, 0.0f, 1.0f }; // MatrixIdentity()

    float a2 = q.x*q.x;
    float b2 = q.y*q.y;
    float c2 = q.z*q.z;
    float ac = q.x*q.z;
    float ab = q.x*q.y;
    float bc = q.y*q.z;
    float ad = q.w*q.x;
    float bd = q.w*q.y;
    float cd = q.w*q.z;

    result.m0 = 1 - 2*(b2 + c2);
    result.m1 = 2*(ab + cd);
    result.m2 = 2*(ac - bd);

    result.m4 = 2*(ab - cd);
    result.m5 = 1 - 2*(a2 + c2);
    result.m6 = 2*(bc + ad);

    result.m8 = 2*(ac + bd);
    result.m9 = 2*(bc - ad);
    result.m10 = 1 - 2*(a2 + b2);

    return result;
}

// Get rotation quaternion for an angle and axis
// NOTE: angle must be provided in radians
static Quaternion QuaternionFromAxisAngle(Vector3 axis, float angle)
{
    Quaternion result = { 0.0f, 0.0f, 0.0f, 1.0f };

    float axisLength = sqrtf(axis.x*axis.x + axis.y*axis.y + axis.z*axis.z);

    if (axisLength != 0.0f)
    {
        angle *= 0.5f;

        float length = 0.0f;
        float ilength = 0.0f;

        // Vector3Normalize(axis)
        Vector3 v = axis;
        length = sqrtf(v.x*v.x + v.y*v.y + v.z*v.z);
        if (length == 0.0f) length = 1.0f;
        ilength = 1.0f/length;
        axis.x *= ilength;
        axis.y *= ilength;
        axis.z *= ilength;

        float sinres = sinf(angle);
        float cosres = cosf(angle);

        result.x = axis.x*sinres;
        result.y = axis.y*sinres;
        result.z = axis.z*sinres;
        result.w = cosres;

        // QuaternionNormalize(q);
        Quaternion q = result;
        length = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);
        if (length == 0.0f) length = 1.0f;
        ilength = 1.0f/length;
        result.x = q.x*ilength;
        result.y = q.y*ilength;
        result.z = q.z*ilength;
        result.w = q.w*ilength;
    }

    return result;
}

// Get the rotation angle and axis for a given quaternion
static void QuaternionToAxisAngle(Quaternion q, Vector3 *outAxis, float *outAngle)
{
    if (fabs(q.w) > 1.0f)
    {
        // QuaternionNormalize(q);
        float length = sqrtf(q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w);
        if (length == 0.0f) length = 1.0f;
        float ilength = 1.0f/length;

        q.x = q.x*ilength;
        q.y = q.y*ilength;
        q.z = q.z*ilength;
        q.w = q.w*ilength;
    }

    Vector3 resAxis = { 0.0f, 0.0f, 0.0f };
    float resAngle = 2.0f*acosf(q.w);
    float den = sqrtf(1.0f - q.w*q.w);

    if (den > 0.0001f)
    {
        resAxis.x = q.x/den;
        resAxis.y = q.y/den;
        resAxis.z = q.z/den;
    }
    else
    {
        // This occurs when the angle is zero.
        // Not a problem: just set an arbitrary normalized axis.
        resAxis.x = 1.0f;
    }

    *outAxis = resAxis;
    *outAngle = resAngle;
}

// Get the quaternion equivalent to Euler angles
// NOTE: Rotation order is ZYX
static Quaternion QuaternionFromEuler(float pitch, float yaw, float roll)
{
    Quaternion result = { 0 };

    float x0 = cosf(pitch*0.5f);
    float x1 = sinf(pitch*0.5f);
    float y0 = cosf(yaw*0.5f);
    float y1 = sinf(yaw*0.5f);
    float z0 = cosf(roll*0.5f);
    float z1 = sinf(roll*0.5f);

    result.x = x1*y0*z0 - x0*y1*z1;
    result.y = x0*y1*z0 + x1*y0*z1;
    result.z = x0*y0*z1 - x1*y1*z0;
    result.w = x0*y0*z0 + x1*y1*z1;

    return result;
}

// Get the Euler angles equivalent to quaternion (roll, pitch, yaw)
// NOTE: Angles are returned in a Vector3 struct in radians
static Vector3 QuaternionToEuler(Quaternion q)
{
    Vector3 result = { 0 };

    // Roll (x-axis rotation)
    float x0 = 2.0f*(q.w*q.x + q.y*q.z);
    float x1 = 1.0f - 2.0f*(q.x*q.x + q.y*q.y);
    result.x = atan2f(x0, x1);

    // Pitch (y-axis rotation)
    float y0 = 2.0f*(q.w*q.y - q.z*q.x);
    y0 = y0 > 1.0f ? 1.0f : y0;
    y0 = y0 < -1.0f ? -1.0f : y0;
    result.y = asinf(y0);

    // Yaw (z-axis rotation)
    float z0 = 2.0f*(q.w*q.z + q.x*q.y);
    float z1 = 1.0f - 2.0f*(q.y*q.y + q.z*q.z);
    result.z = atan2f(z0, z1);

    return result;
}

// Transform a quaternion given a transformation matrix
static Quaternion QuaternionTransform(Quaternion q, Matrix mat)
{
    Quaternion result = { 0 };

    result.x = mat.m0*q.x + mat.m4*q.y + mat.m8*q.z + mat.m12*q.w;
    result.y = mat.m1*q.x + mat.m5*q.y + mat.m9*q.z + mat.m13*q.w;
    result.z = mat.m2*q.x + mat.m6*q.y + mat.m10*q.z + mat.m14*q.w;
    result.w = mat.m3*q.x + mat.m7*q.y + mat.m11*q.z + mat.m15*q.w;

    return result;
}