#ifndef LINMATH_H
#define LINMATH_H

/* Credit : https://github.com/datenwolf/linmath.h */

#include "../include/kazmath/kazmath/kazmath.h"
#include "../include/kazmath/kazmath/vec4.h"
#include <math.h>

/* Just for convenience & consistency */
typedef kmVec2        vec2;
typedef kmVec3        vec3;
typedef struct kmVec4 vec4;
typedef kmMat3        mat3;
typedef kmMat4        mat4;
typedef kmQuaternion  quat;

/* vec3 */
#define vec3_fill           kmVec3Fill
#define vec3_add            kmVec3Add
#define vec3_assign         kmVec3Assign
#define vec3_norm           kmVec3Normalize
#define vec3_mul            kmVec3Mul
#define vec3_mul_mat4       kmVec3MultiplyMat4
#define vec3_mul_mat3       kmVec3MultiplyMat3
#define vec3_scale          kmVec3Scale
#define vec3_equals         kmVec3Equals
#define vec3_transform      kmVec3Transform
#define vec3_transform_norm kmVec3TransformNormal
#define vec3_len            kmVec3Length

/* vec4 */
#define vec4_fill           kmVec4Fill
#define vec4_add            kmVec4Add
#define vec4_assign         kmVec4Assign
#define vec4_norm           kmVec4Normalize
#define vec4_mul            kmVec4Mul
#define vec4_mul_mat4       kmVec4MultiplyMat4
#define vec4_scale          kmVec4Scale
#define vec4_equals         kmVec4Equals
#define vec4_transform      kmVec4Transform
#define vec4_transform_norm kmVec4TransformNormal
#define vec4_len            kmVec4Length

/* mat4 */
#define mat4_identity    kmMat4Identity
#define mat4_mul         kmMat4Multiply
#define mat4_lookat      kmMat4LookAt
#define mat4_perspective kmMat4PerspectiveProjection
#define mat4_ortho       kmMat4OrthographicProjection
#define mat4_scale       kmMat4Scaling
#define mat4_translate   kmMat4Translation
#define mat4_from_quat   kmMat4RotationQuaternion
#define mat4_rot_x       kmMat4RotationX
#define mat4_rot_y       kmMat4RotationY
#define mat4_rot_z       kmMat4RotationZ

/* quat */
#define quat_identity       kmQuaternionIdentity
#define quat_mul_vec3       kmQuaternionMultiplyVec3
#define quat_mul            kmQuaternionMultiply
#define quat_axis_angle     kmQuaternionRotationAxisAngle
#define quat_get_forward_rh kmQuaternionGetForwardVec3RH
#define quat_get_forward_lh kmQuaternionGetForwardVec3LH
#define quat_get_up         kmQuaternionGetUpVec3
#define quat_get_right      kmQuaternionGetRightVec3


#define M_PI		        3.14159265358979323846 
#define TO_RADIANS(degrees) ((degrees * M_PI) / 180.0)
#define TO_DEGREES(radians) ((radians * 180.0) / M_PI)

/* #define LINMATH_H_DEFINE_VEC(n)											\ */
/* 	typedef float vec##n[n];											\ */
/* 	static inline void vec##n##_add(vec##n r, vec##n const a, vec##n const b) \ */
/* 	{																	\ */
/* 		int i;															\ */
/* 		for(i=0; i<n; ++i)												\ */
/* 			r[i] = a[i] + b[i];											\ */
/* 	}																	\ */
/* 	static inline void vec##n##_sub(vec##n r, vec##n const a, vec##n const b) \ */
/* 	{																	\ */
/* 		int i;															\ */
/* 		for(i=0; i<n; ++i)												\ */
/* 			r[i] = a[i] - b[i];											\ */
/* 	}																	\ */
/* 	static inline void vec##n##_scale(vec##n r, vec##n const v, float const s) \ */
/* 	{																	\ */
/* 		int i;															\ */
/* 		for(i=0; i<n; ++i)												\ */
/* 			r[i] = v[i] * s;											\ */
/* 	}																	\ */
/* 	static inline float vec##n##_mul_inner(vec##n const a, vec##n const b) \ */
/* 	{																	\ */
/* 		float p = 0.;													\ */
/* 		int i;															\ */
/* 		for(i=0; i<n; ++i)												\ */
/* 			p += b[i]*a[i];												\ */
/* 		return p;														\ */
/* 	}																	\ */
/* 	static inline float vec##n##_len(vec##n const v)					\ */
/* 	{																	\ */
/* 		return sqrtf(vec##n##_mul_inner(v,v));							\ */
/* 	}																	\ */
/* 	static inline void vec##n##_norm(vec##n r, vec##n const v)			\ */
/* 	{																	\ */
/* 		float k = 1.0 / vec##n##_len(v);								\ */
/* 		vec##n##_scale(r, v, k);										\ */
/* 	} */

/* LINMATH_H_DEFINE_VEC(2) */
/* LINMATH_H_DEFINE_VEC(3) */
/* LINMATH_H_DEFINE_VEC(4) */

/* static inline void vec3_mul_cross(vec3 r, vec3 const a, vec3 const b) */
/* { */
/* 	r[0] = a[1]*b[2] - a[2]*b[1]; */
/* 	r[1] = a[2]*b[0] - a[0]*b[2]; */
/* 	r[2] = a[0]*b[1] - a[1]*b[0]; */
/* } */

/* static inline void vec3_reflect(vec3 r, vec3 const v, vec3 const n) */
/* { */
/* 	float p  = 2.f*vec3_mul_inner(v, n); */
/* 	int i; */
/* 	for(i=0;i<3;++i) */
/* 		r[i] = v[i] - p*n[i]; */
/* } */

/* static inline void vec4_mul_cross(vec4 r, vec4 a, vec4 b) */
/* { */
/* 	r[0] = a[1]*b[2] - a[2]*b[1]; */
/* 	r[1] = a[2]*b[0] - a[0]*b[2]; */
/* 	r[2] = a[0]*b[1] - a[1]*b[0]; */
/* 	r[3] = 1.f; */
/* } */

/* static inline void vec4_reflect(vec4 r, vec4 v, vec4 n) */
/* { */
/* 	float p  = 2.f*vec4_mul_inner(v, n); */
/* 	int i; */
/* 	for(i=0;i<4;++i) */
/* 		r[i] = v[i] - p*n[i]; */
/* } */

/* typedef vec4 mat4[4]; */
/* static inline void mat4_identity(mat4 M) */
/* { */
/* 	int i, j; */
/* 	for(i=0; i<4; ++i) */
/* 		for(j=0; j<4; ++j) */
/* 			M[i][j] = i==j ? 1.f : 0.f; */
/* } */
/* static inline void mat4_dup(mat4 M, mat4 N) */
/* { */
/* 	int i, j; */
/* 	for(i=0; i<4; ++i) */
/* 		for(j=0; j<4; ++j) */
/* 			M[i][j] = N[i][j]; */
/* } */
/* static inline void mat4_row(vec4 r, mat4 M, int i) */
/* { */
/* 	int k; */
/* 	for(k=0; k<4; ++k) */
/* 		r[k] = M[k][i]; */
/* } */
/* static inline void mat4_col(vec4 r, mat4 M, int i) */
/* { */
/* 	int k; */
/* 	for(k=0; k<4; ++k) */
/* 		r[k] = M[i][k]; */
/* } */
/* static inline void mat4_transpose(mat4 M, mat4 N) */
/* { */
/* 	int i, j; */
/* 	for(j=0; j<4; ++j) */
/* 		for(i=0; i<4; ++i) */
/* 			M[i][j] = N[j][i]; */
/* } */
/* static inline void mat4_add(mat4 M, mat4 a, mat4 b) */
/* { */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		vec4_add(M[i], a[i], b[i]); */
/* } */
/* static inline void mat4_sub(mat4 M, mat4 a, mat4 b) */
/* { */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		vec4_sub(M[i], a[i], b[i]); */
/* } */
/* static inline void mat4_scale(mat4 M, mat4 a, float k) */
/* { */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		vec4_scale(M[i], a[i], k); */
/* } */
/* static inline void mat4_scale_aniso(mat4 M, mat4 a, float x, float y, float z) */
/* { */
/* 	/\* int i; *\/ */
/* 	/\* vec4_scale(M[0], a[0], x); *\/ */
/* 	/\* vec4_scale(M[1], a[1], y); *\/ */
/* 	/\* vec4_scale(M[2], a[2], z); *\/ */
/* 	/\* for(i = 0; i < 4; ++i) { *\/ */
/* 	/\* 	M[3][i] = a[3][i]; *\/ */
/* 	/\* } *\/ */

/* 	M[0][0] = a[0][0] * x; */
/* 	M[1][1] = a[1][1] * y; */
/* 	M[2][2] = a[2][2] * z; */
/* 	M[3][3] = 1.f; */
/* } */
/* static inline void mat4_mul(mat4 M, mat4 a, mat4 b) */
/* { */
/* 	mat4 temp; */
/* 	/\* int k, r, c; *\/ */
/* 	/\* for(c=0; c<4; ++c) for(r=0; r<4; ++r) { *\/ */
/* 	/\* 	temp[c][r] = 0.f; *\/ */
/* 	/\* 	for(k=0; k<4; ++k) *\/ */
/* 	/\* 		temp[c][r] += a[k][r] * b[c][k]; *\/ */
/* 	/\* } *\/ */

/* 	temp[0][0] = a[0][0] * b[0][0]  + a[1][0] * b[0][1]  + a[2][0] * b[0][2]  + a[3][0] * b[0][3]; */
/*     temp[1][0] = a[0][0] * b[1][0]  + a[1][0] * b[1][1]  + a[2][0] * b[1][2]  + a[3][0] * b[1][3]; */
/*     temp[2][0] = a[0][0] * b[2][0]  + a[1][0] * b[2][1]  + a[2][0] * b[2][2]  + a[3][0] * b[2][3]; */
/*     temp[3][0] = a[0][0] * b[3][0]  + a[1][0] * b[3][1]  + a[2][0] * b[3][2]  + a[3][0] * b[3][3]; */
/*     temp[0][1] = a[0][1] * b[0][0]  + a[1][1] * b[0][1]  + a[2][1] * b[0][2]  + a[3][1] * b[0][3]; */
/*     temp[1][1] = a[0][1] * b[1][0]  + a[1][1] * b[1][1]  + a[2][1] * b[1][2]  + a[3][1] * b[1][3]; */
/*     temp[2][1] = a[0][1] * b[2][0]  + a[1][1] * b[2][1]  + a[2][1] * b[2][2]  + a[3][1] * b[2][3]; */
/*     temp[3][1] = a[0][1] * b[3][0]  + a[1][1] * b[3][1]  + a[2][1] * b[3][2]  + a[3][1] * b[3][3]; */
/*     temp[0][2] = a[0][2] * b[0][0]  + a[1][2] * b[0][1]  + a[2][2] * b[0][2]  + a[3][2] * b[0][3]; */
/*     temp[1][2] = a[0][2] * b[1][0]  + a[1][2] * b[1][1]  + a[2][2] * b[1][2]  + a[3][2] * b[1][3]; */
/*     temp[2][2] = a[0][2] * b[2][0]  + a[1][2] * b[2][1]  + a[2][2] * b[2][2]  + a[3][2] * b[2][3]; */
/*     temp[3][2] = a[0][2] * b[3][0]  + a[1][2] * b[3][1]  + a[2][2] * b[3][2]  + a[3][2] * b[3][3]; */
/*     temp[0][3] = a[0][3] * b[0][0]  + a[1][3] * b[0][1]  + a[2][3] * b[0][2]  + a[3][3] * b[0][3]; */
/*     temp[1][3] = a[0][3] * b[1][0]  + a[1][3] * b[1][1]  + a[2][3] * b[1][2]  + a[3][3] * b[1][3]; */
/*     temp[2][3] = a[0][3] * b[2][0]  + a[1][3] * b[2][1]  + a[2][3] * b[2][2]  + a[3][3] * b[2][3]; */
/*     temp[3][3] = a[0][3] * b[3][0]  + a[1][3] * b[3][1]  + a[2][3] * b[3][2]  + a[3][3] * b[3][3]; */

/* 	mat4_dup(M, temp); */
/* } */
/* static inline void mat4_mul_vec4(vec4 r, mat4 M, vec4 v) */
/* { */
/* 	/\* int i, j; *\/ */
/* 	/\* for(j=0; j<4; ++j) { *\/ */
/* 	/\* 	r[j] = 0.f; *\/ */
/* 	/\* 	for(i=0; i<4; ++i) *\/ */
/* 	/\* 		r[j] += M[i][j] * v[i]; *\/ */
/* 	/\* } *\/ */
/* 	r[0] = (M[0][0] * v[0]) + (M[0][1] * v[1]) + (M[0][2] * v[2]) + (M[0][3] * v[3]); */
/* 	r[1] = (M[1][0] * v[0]) + (M[1][1] * v[1]) + (M[1][2] * v[2]) + (M[1][3] * v[3]); */
/* 	r[2] = (M[2][0] * v[0]) + (M[2][1] * v[1]) + (M[2][2] * v[2]) + (M[2][3] * v[3]); */
/* 	r[3] = (M[3][0] * v[0]) + (M[3][1] * v[1]) + (M[3][2] * v[2]) + (M[3][3] * v[3]); */
/* } */
/* static inline void mat4_mul_vec3(vec3 r, mat4 M, vec3 v) */
/* { */
/* 	/\* vec4 temp; *\/ */
/* 	/\* for(int i = 0; i < 3; i++) *\/ */
/* 	/\* 	temp[i] = v[i]; *\/ */
/* 	/\* temp[3] = 1.f; *\/ */
/* 	/\* mat4_mul_vec4(temp, M, temp); *\/ */
/* 	/\* for(int i = 0; i < 3; i++) *\/ */
/* 	/\* 	r[i] = temp[i]; *\/ */
/* 	r[0] = (M[0][0] * v[0]) + (M[0][1] * v[1]) + (M[0][2] * v[2]) + (M[0][3]); */
/* 	r[1] = (M[1][0] * v[0]) + (M[1][1] * v[1]) + (M[1][2] * v[2]) + (M[1][3]); */
/* 	r[2] = (M[2][0] * v[0]) + (M[2][1] * v[1]) + (M[2][2] * v[2]) + (M[2][3]); */
/* } */
/* static inline void mat4_translate(mat4 T, float x, float y, float z) */
/* { */
/* 	mat4_identity(T); */
/* 	T[3][0] = x; */
/* 	T[3][1] = y; */
/* 	T[3][2] = z; */
/* } */
/* static inline void mat4_translate_in_place(mat4 M, float x, float y, float z) */
/* { */
/* 	vec4 t = {x, y, z, 0}; */
/* 	vec4 r; */
/* 	int i; */
/* 	for (i = 0; i < 4; ++i) { */
/* 		mat4_row(r, M, i); */
/* 		M[3][i] += vec4_mul_inner(r, t); */
/* 	} */
/* } */
/* static inline void mat4_from_vec3_mul_outer(mat4 M, vec3 a, vec3 b) */
/* { */
/* 	int i, j; */
/* 	for(i=0; i<4; ++i) for(j=0; j<4; ++j) */
/* 		M[i][j] = i<3 && j<3 ? a[i] * b[j] : 0.f; */
/* } */
/* static inline void mat4_rotate(mat4 R, mat4 M, float x, float y, float z, float angle) */
/* { */
/* 	float s = sinf(angle); */
/* 	float c = cosf(angle); */
/* 	vec3 u = {x, y, z}; */

/* 	if(vec3_len(u) > 1e-4) { */
/* 		vec3_norm(u, u); */
/* 		mat4 T; */
/* 		mat4_from_vec3_mul_outer(T, u, u); */

/* 		mat4 S = { */
/* 			{    0,  u[2], -u[1], 0}, */
/* 			{-u[2],     0,  u[0], 0}, */
/* 			{ u[1], -u[0],     0, 0}, */
/* 			{    0,     0,     0, 0} */
/* 		}; */
/* 		mat4_scale(S, S, s); */

/* 		mat4 C; */
/* 		mat4_identity(C); */
/* 		mat4_sub(C, C, T); */

/* 		mat4_scale(C, C, c); */

/* 		mat4_add(T, T, C); */
/* 		mat4_add(T, T, S); */

/* 		T[3][3] = 1.;		 */
/* 		mat4_mul(R, M, T); */
/* 	} else { */
/* 		mat4_dup(R, M); */
/* 	} */
/* } */
/* static inline void mat4_rotate_X(mat4 Q, mat4 M, float angle) */
/* { */
/* 	float s = sinf(angle); */
/* 	float c = cosf(angle); */
/* 	mat4 R = { */
/* 		{1.f, 0.f, 0.f, 0.f}, */
/* 		{0.f,   c,   s, 0.f}, */
/* 		{0.f,  -s,   c, 0.f}, */
/* 		{0.f, 0.f, 0.f, 1.f} */
/* 	}; */
/* 	mat4_mul(Q, M, R); */
/* } */
/* static inline void mat4_rotate_Y(mat4 Q, mat4 M, float angle) */
/* { */
/* 	float s = sinf(angle); */
/* 	float c = cosf(angle); */
/* 	mat4 R = { */
/* 		{   c, 0.f,   s, 0.f}, */
/* 		{ 0.f, 1.f, 0.f, 0.f}, */
/* 		{  -s, 0.f,   c, 0.f}, */
/* 		{ 0.f, 0.f, 0.f, 1.f} */
/* 	}; */
/* 	mat4_mul(Q, M, R); */
/* } */
/* static inline void mat4_rotate_Z(mat4 Q, mat4 M, float angle) */
/* { */
/* 	float s = sinf(angle); */
/* 	float c = cosf(angle); */
/* 	mat4 R = { */
/* 		{   c,   s, 0.f, 0.f}, */
/* 		{  -s,   c, 0.f, 0.f}, */
/* 		{ 0.f, 0.f, 1.f, 0.f}, */
/* 		{ 0.f, 0.f, 0.f, 1.f} */
/* 	}; */
/* 	mat4_mul(Q, M, R); */
/* } */
/* static inline void mat4_invert(mat4 T, mat4 M) */
/* { */
/* 	float s[6]; */
/* 	float c[6]; */
/* 	s[0] = M[0][0]*M[1][1] - M[1][0]*M[0][1]; */
/* 	s[1] = M[0][0]*M[1][2] - M[1][0]*M[0][2]; */
/* 	s[2] = M[0][0]*M[1][3] - M[1][0]*M[0][3]; */
/* 	s[3] = M[0][1]*M[1][2] - M[1][1]*M[0][2]; */
/* 	s[4] = M[0][1]*M[1][3] - M[1][1]*M[0][3]; */
/* 	s[5] = M[0][2]*M[1][3] - M[1][2]*M[0][3]; */

/* 	c[0] = M[2][0]*M[3][1] - M[3][0]*M[2][1]; */
/* 	c[1] = M[2][0]*M[3][2] - M[3][0]*M[2][2]; */
/* 	c[2] = M[2][0]*M[3][3] - M[3][0]*M[2][3]; */
/* 	c[3] = M[2][1]*M[3][2] - M[3][1]*M[2][2]; */
/* 	c[4] = M[2][1]*M[3][3] - M[3][1]*M[2][3]; */
/* 	c[5] = M[2][2]*M[3][3] - M[3][2]*M[2][3]; */
	
/* 	/\* Assumes it is invertible *\/ */
/* 	float idet = 1.0f/( s[0]*c[5]-s[1]*c[4]+s[2]*c[3]+s[3]*c[2]-s[4]*c[1]+s[5]*c[0] ); */
	
/* 	T[0][0] = ( M[1][1] * c[5] - M[1][2] * c[4] + M[1][3] * c[3]) * idet; */
/* 	T[0][1] = (-M[0][1] * c[5] + M[0][2] * c[4] - M[0][3] * c[3]) * idet; */
/* 	T[0][2] = ( M[3][1] * s[5] - M[3][2] * s[4] + M[3][3] * s[3]) * idet; */
/* 	T[0][3] = (-M[2][1] * s[5] + M[2][2] * s[4] - M[2][3] * s[3]) * idet; */

/* 	T[1][0] = (-M[1][0] * c[5] + M[1][2] * c[2] - M[1][3] * c[1]) * idet; */
/* 	T[1][1] = ( M[0][0] * c[5] - M[0][2] * c[2] + M[0][3] * c[1]) * idet; */
/* 	T[1][2] = (-M[3][0] * s[5] + M[3][2] * s[2] - M[3][3] * s[1]) * idet; */
/* 	T[1][3] = ( M[2][0] * s[5] - M[2][2] * s[2] + M[2][3] * s[1]) * idet; */

/* 	T[2][0] = ( M[1][0] * c[4] - M[1][1] * c[2] + M[1][3] * c[0]) * idet; */
/* 	T[2][1] = (-M[0][0] * c[4] + M[0][1] * c[2] - M[0][3] * c[0]) * idet; */
/* 	T[2][2] = ( M[3][0] * s[4] - M[3][1] * s[2] + M[3][3] * s[0]) * idet; */
/* 	T[2][3] = (-M[2][0] * s[4] + M[2][1] * s[2] - M[2][3] * s[0]) * idet; */

/* 	T[3][0] = (-M[1][0] * c[3] + M[1][1] * c[1] - M[1][2] * c[0]) * idet; */
/* 	T[3][1] = ( M[0][0] * c[3] - M[0][1] * c[1] + M[0][2] * c[0]) * idet; */
/* 	T[3][2] = (-M[3][0] * s[3] + M[3][1] * s[1] - M[3][2] * s[0]) * idet; */
/* 	T[3][3] = ( M[2][0] * s[3] - M[2][1] * s[1] + M[2][2] * s[0]) * idet; */
/* } */
/* static inline void mat4_orthonormalize(mat4 R, mat4 M) */
/* { */
/* 	mat4_dup(R, M); */
/* 	float s = 1.; */
/* 	vec3 h; */

/* 	vec3_norm(R[2], R[2]); */
	
/* 	s = vec3_mul_inner(R[1], R[2]); */
/* 	vec3_scale(h, R[2], s); */
/* 	vec3_sub(R[1], R[1], h); */
/* 	vec3_norm(R[2], R[2]); */

/* 	s = vec3_mul_inner(R[1], R[2]); */
/* 	vec3_scale(h, R[2], s); */
/* 	vec3_sub(R[1], R[1], h); */
/* 	vec3_norm(R[1], R[1]); */

/* 	s = vec3_mul_inner(R[0], R[1]); */
/* 	vec3_scale(h, R[1], s); */
/* 	vec3_sub(R[0], R[0], h); */
/* 	vec3_norm(R[0], R[0]); */
/* } */

/* static inline void mat4_frustum(mat4 M, float l, float r, float b, float t, float n, float f) */
/* { */
/* 	M[0][0] = 2.f*n/(r-l); */
/* 	M[0][1] = M[0][2] = M[0][3] = 0.f; */
	
/* 	M[1][1] = 2.*n/(t-b); */
/* 	M[1][0] = M[1][2] = M[1][3] = 0.f; */

/* 	M[2][0] = (r+l)/(r-l); */
/* 	M[2][1] = (t+b)/(t-b); */
/* 	M[2][2] = -(f+n)/(f-n); */
/* 	M[2][3] = -1.f; */
	
/* 	M[3][2] = -2.f*(f*n)/(f-n); */
/* 	M[3][0] = M[3][1] = M[3][3] = 0.f; */
/* } */
/* static inline void mat4_ortho(mat4 M, float l, float r, float b, float t, float n, float f) */
/* { */
/* 	M[0][0] = 2.f/(r-l); */
/* 	M[0][1] = M[0][2] = M[0][3] = 0.f; */

/* 	M[1][1] = 2.f/(t-b); */
/* 	M[1][0] = M[1][2] = M[1][3] = 0.f; */

/* 	M[2][2] = -2.f/(f-n); */
/* 	M[2][0] = M[2][1] = M[2][3] = 0.f; */
	
/* 	M[3][0] = -(r+l)/(r-l); */
/* 	M[3][1] = -(t+b)/(t-b); */
/* 	M[3][2] = -(f+n)/(f-n); */
/* 	M[3][3] = 1.f; */
/* } */
/* static inline void mat4_perspective(mat4 m, float y_fov, float aspect, float n, float f) */
/* { */
/* 	/\* NOTE: Degrees are an unhandy unit to work with. */
/* 	 * linmath.h uses radians for everything! *\/ */
/* 	float const a = 1.f / tan(y_fov / 2.f); */

/* 	m[0][0] = a / aspect; */
/* 	m[0][1] = 0.f; */
/* 	m[0][2] = 0.f; */
/* 	m[0][3] = 0.f; */

/* 	m[1][0] = 0.f; */
/* 	m[1][1] = a; */
/* 	m[1][2] = 0.f; */
/* 	m[1][3] = 0.f; */

/* 	m[2][0] = 0.f; */
/* 	m[2][1] = 0.f; */
/* 	m[2][2] = -((f + n) / (f - n)); */
/* 	m[2][3] = -1.f; */

/* 	m[3][0] = 0.f; */
/* 	m[3][1] = 0.f; */
/* 	m[3][2] = -((2.f * f * n) / (f - n)); */
/* 	m[3][3] = 0.f; */
/* } */
/* static inline void mat4_look_at(mat4 m, vec3 eye, vec3 lookat, vec3 up) */
/* { */
/* 	/\* Adapted from Android's OpenGL Matrix.java.                        *\/ */
/* 	/\* See the OpenGL GLUT documentation for gluLookAt for a description *\/ */
/* 	/\* of the algorithm. We implement it in a straightforward way:       *\/ */

/* 	/\* TODO: The negation of of can be spared by swapping the order of */
/* 	 *       operands in the following cross products in the right way. *\/ */
/* 	vec3 f; */
/* 	vec3_sub(f, lookat, eye); */
/* 	vec3_norm(f, f);	 */
	
/* 	vec3 s; */
/* 	vec3_mul_cross(s, f, up); */
/* 	vec3_norm(s, s); */

/* 	vec3 t; */
/* 	vec3_mul_cross(t, s, f); */

/* 	m[0][0] =  s[0]; */
/* 	m[1][0] =  s[1]; */
/* 	m[2][0] =  s[2]; */
	
/* 	m[0][1] =  t[0]; */
/* 	m[1][1] =  t[1]; */
/* 	m[2][1] =  t[2]; */
	
/* 	m[0][2] = -f[0]; */
/* 	m[1][2] = -f[1]; */
/* 	m[2][2] = -f[2]; */
	
/* 	m[0][3] =   0.f; */
/* 	m[1][3] =   0.f; */
/* 	m[2][3] =   0.f; */

/* 	m[3][0] =  -vec3_mul_inner(s, eye); */
/* 	m[3][1] =  -vec3_mul_inner(t, eye); */
/* 	m[3][2] =   vec3_mul_inner(f, eye); */
/* 	m[3][3] =  1.f; */

/* 	//mat4_translate_in_place(m, -eye[0], -eye[1], -eye[2]); */
/* } */

/* typedef float quat[4]; */
/* static inline void quat_identity(quat q) */
/* { */
/* 	q[0] = q[1] = q[2] = 0.f; */
/* 	q[3] = 1.f; */
/* } */
/* static inline void quat_add(quat r, quat a, quat b) */
/* { */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		r[i] = a[i] + b[i]; */
/* } */
/* static inline void quat_sub(quat r, quat a, quat b) */
/* { */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		r[i] = a[i] - b[i]; */
/* } */
/* static inline void quat_mul(quat r, quat p, quat q) */
/* { */
/* 	/\* vec3 w; *\/ */
/* 	/\* vec3_mul_cross(r, p, q); *\/ */
/* 	/\* vec3_scale(w, p, q[3]); *\/ */
/* 	/\* vec3_add(r, r, w); *\/ */
/* 	/\* vec3_scale(w, q, p[3]); *\/ */
/* 	/\* vec3_add(r, r, w); *\/ */
/* 	/\* r[3] = p[3]*q[3] - vec3_mul_inner(p, q); *\/ */

/* 	r[0] = (p[3] * q[0]) + (p[0] * q[3]) + (p[1] * q[2]) - (p[2] * q[1]); */
/* 	r[1] = (p[3] * q[1]) + (p[1] * q[3]) + (p[2] * q[0]) - (p[0] * q[2]); */
/* 	r[2] = (p[3] * q[2]) + (p[2] * q[3]) + (p[0] * q[1]) - (p[1] * q[0]); */
/* 	r[3] = (p[3] * q[3]) - (p[0] * q[0]) - (p[1] * q[1]) - (p[2] * q[2]); */
/* } */
/* static inline void quat_scale(quat r, quat v, float s) */
/* { */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		r[i] = v[i] * s; */
/* } */
/* static inline float quat_inner_product(quat a, quat b) */
/* { */
/* 	float p = 0.f; */
/* 	int i; */
/* 	for(i=0; i<4; ++i) */
/* 		p += b[i]*a[i]; */
/* 	return p; */
/* } */
/* static inline void quat_conj(quat r, quat q) */
/* { */
/* 	int i; */
/* 	for(i=0; i<3; ++i) */
/* 		r[i] = -q[i]; */
/* 	r[3] = q[3]; */
/* } */
/* static inline void quat_rotate(quat r, float angle, vec3 axis) { */
/* 	vec3 v; */
/* 	vec3_scale(v, axis, sinf(angle / 2.f)); */
/* 	int i; */
/* 	for(i=0; i<3; ++i) */
/* 		r[i] = v[i]; */
/* 	r[3] = cosf(angle / 2.f); */
/* } */
/* #define quat_norm vec4_norm */
/* static inline void quat_mul_vec3(vec3 r, quat q, vec3 v) */
/* { */
/* /\* */
/*  * Method by Fabian 'ryg' Giessen (of Farbrausch) */
/*  t = 2 * cross(q.xyz, v) */
/*  v' = v + q.w * t + cross(q.xyz, t) */
/* *\/ */
/* 	vec3 t = {q[0], q[1], q[2]}; */
/* 	vec3 u = {q[0], q[1], q[2]}; */

/* 	vec3_mul_cross(t, t, v); */
/* 	vec3_scale(t, t, 2.f); */

/* 	vec3_mul_cross(u, u, t); */
/* 	vec3_scale(t, t, q[3]); */

/* 	vec3_add(r, v, t); */
/* 	vec3_add(r, r, u); */
/* } */
/* static inline float quat_pitch(quat q) */
/* { */
/*     float result = atan2(2 * (q[1] * q[2] + q[3] * q[0]), q[3] * q[3] - q[0] * q[0] - q[1] * q[1] + q[2] * q[2]); */
/*     return result; */
/* } */

/* static inline float quat_yaw(quat q) */
/* { */
/*     float result = asin(-2 * (q[0] * q[2] - q[3] * q[1])); */
/*     return result; */
/* } */
/* static inline float quat_roll(quat q) */
/* { */
/*     float result = atan2(2 * (q[0] * q[1] + q[3] * q[2]), q[3] * q[3] + q[0] * q[0] - q[1] * q[1] - q[2] * q[2]); */
/*     return result; */
/* } */
/* static inline void mat4_from_quat(mat4 M, quat q) */
/* { */
/* 	/\* float a = q[3]; *\/ */
/* 	/\* float b = q[0]; *\/ */
/* 	/\* float c = q[1]; *\/ */
/* 	/\* float d = q[2]; *\/ */
/* 	/\* float a2 = a*a; *\/ */
/* 	/\* float b2 = b*b; *\/ */
/* 	/\* float c2 = c*c; *\/ */
/* 	/\* float d2 = d*d; *\/ */
	
/* 	/\* M[0][0] = a2 + b2 - c2 - d2; *\/ */
/* 	/\* M[0][1] = 2.f*(b*c + a*d); *\/ */
/* 	/\* M[0][2] = 2.f*(b*d - a*c); *\/ */
/* 	/\* M[0][3] = 0.f; *\/ */

/* 	/\* M[1][0] = 2*(b*c - a*d); *\/ */
/* 	/\* M[1][1] = a2 - b2 + c2 - d2; *\/ */
/* 	/\* M[1][2] = 2.f*(c*d + a*b); *\/ */
/* 	/\* M[1][3] = 0.f; *\/ */

/* 	/\* M[2][0] = 2.f*(b*d + a*c); *\/ */
/* 	/\* M[2][1] = 2.f*(c*d - a*b); *\/ */
/* 	/\* M[2][2] = a2 - b2 - c2 + d2; *\/ */
/* 	/\* M[2][3] = 0.f; *\/ */

/* 	/\* M[3][0] = M[3][1] = M[3][2] = 0.f; *\/ */
/* 	/\* M[3][3] = 1.f; *\/ */

/* 	float xx = q[0] * q[0]; */
/*     float xy = q[0] * q[1]; */
/*     float xz = q[0] * q[2]; */

/*     float yy = q[1] * q[1]; */
/*     float yz = q[1] * q[2]; */

/*     float zz = q[2] * q[2]; */
/*     float wz = q[3] * q[2]; */
/*     float wy = q[3] * q[1]; */
/*     float wx = q[3] * q[0]; */

/*     M[0][0] = 1 - 2 * (yy + zz); */
/*     M[0][1] = 2 * (xy + wz); */
/*     M[0][2] = 2 * (xz - wy); */
/*     M[0][3] = 0; */

/*     M[1][0] = 2 * (xy - wz); */
/*     M[1][1] = 1 - 2 * (xx + zz); */
/*     M[1][2] = 2 * (yz + wx); */
/*     M[1][3] = 0.0; */

/*     M[2][0] = 2 * (xz + wy); */
/*     M[2][1] = 2 * (yz - wx); */
/*     M[2][2] = 1 - 2 * (xx + yy); */
/*     M[2][3] = 0.0; */
	
/* 	M[3][0] = M[3][1] = M[3][2] = 0.f; */
/* 	M[3][3] = 1.f; */
/* } */

/* static inline void mat4o_mul_quat(mat4 R, mat4 M, quat q) */
/* { */
/* /\*  XXX: The way this is written only works for othogonal matrices. *\/ */
/* /\* TODO: Take care of non-orthogonal case. *\/ */
/* 	quat_mul_vec3(R[0], q, M[0]); */
/* 	quat_mul_vec3(R[1], q, M[1]); */
/* 	quat_mul_vec3(R[2], q, M[2]); */

/* 	R[3][0] = R[3][1] = R[3][2] = 0.f; */
/* 	R[3][3] = 1.f; */
/* } */
/* static inline void quat_from_mat4(quat q, mat4 M) */
/* { */
/* 	float r=0.f; */
/* 	int i; */

/* 	int perm[] = { 0, 1, 2, 0, 1 }; */
/* 	int *p = perm; */

/* 	for(i = 0; i<3; i++) { */
/* 		float m = M[i][i]; */
/* 		if( m < r ) */
/* 			continue; */
/* 		m = r; */
/* 		p = &perm[i]; */
/* 	} */

/* 	r = sqrtf(1.f + M[p[0]][p[0]] - M[p[1]][p[1]] - M[p[2]][p[2]] ); */

/* 	if(r < 1e-6) { */
/* 		q[0] = 1.f; */
/* 		q[1] = q[2] = q[3] = 0.f; */
/* 		return; */
/* 	} */

/* 	q[0] = r/2.f; */
/* 	q[1] = (M[p[0]][p[1]] - M[p[1]][p[0]])/(2.f*r); */
/* 	q[2] = (M[p[2]][p[0]] - M[p[0]][p[2]])/(2.f*r); */
/* 	q[3] = (M[p[2]][p[1]] - M[p[1]][p[2]])/(2.f*r); */
/* } */

#endif