lots of things aaaaaaaa

Signed-off-by: Anna (navi) Figueiredo Gomes <navi@vlhl.dev>

1 files changed, 605 insertions, 0 deletions

diff --git a/linmath.h b/linmath.h
new file mode 100644
index 0000000..dd329e1
--- /dev/null
+++ b/linmath.h
@@ -0,0 +1,605 @@
+#ifndef LINMATH_H
+#define LINMATH_H
+
+#include <string.h>
+#include <math.h>
+#include <string.h>
+
+#ifdef LINMATH_NO_INLINE
+#define LINMATH_H_FUNC static
+#else
+#define LINMATH_H_FUNC static inline
+#endif
+
+#define LINMATH_H_DEFINE_VEC(n) \
+typedef float vec##n[n]; \
+LINMATH_H_FUNC 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]; \
+} \
+LINMATH_H_FUNC 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]; \
+} \
+LINMATH_H_FUNC 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; \
+} \
+LINMATH_H_FUNC float vec##n##_mul_inner(vec##n const a, vec##n const b) \
+{ \
+	float p = 0.f; \
+	int i; \
+	for(i=0; i<n; ++i) \
+		p += b[i]*a[i]; \
+	return p; \
+} \
+LINMATH_H_FUNC float vec##n##_len(vec##n const v) \
+{ \
+	return sqrtf(vec##n##_mul_inner(v,v)); \
+} \
+LINMATH_H_FUNC void vec##n##_norm(vec##n r, vec##n const v) \
+{ \
+	float k = 1.f / vec##n##_len(v); \
+	vec##n##_scale(r, v, k); \
+} \
+LINMATH_H_FUNC void vec##n##_min(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] ? a[i] : b[i]; \
+} \
+LINMATH_H_FUNC void vec##n##_max(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] ? a[i] : b[i]; \
+} \
+LINMATH_H_FUNC void vec##n##_dup(vec##n r, vec##n const src) \
+{ \
+	int i; \
+	for(i=0; i<n; ++i) \
+		r[i] = src[i]; \
+}
+
+LINMATH_H_DEFINE_VEC(2)
+LINMATH_H_DEFINE_VEC(3)
+LINMATH_H_DEFINE_VEC(4)
+
+LINMATH_H_FUNC 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];
+}
+
+LINMATH_H_FUNC 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];
+}
+
+LINMATH_H_FUNC void vec4_mul_cross(vec4 r, vec4 const a, vec4 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];
+	r[3] = 1.f;
+}
+
+LINMATH_H_FUNC void vec4_reflect(vec4 r, vec4 const v, vec4 const 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 mat4x4[4];
+LINMATH_H_FUNC void mat4x4_identity(mat4x4 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;
+}
+LINMATH_H_FUNC void mat4x4_dup(mat4x4 M, mat4x4 const N)
+{
+	int i;
+	for(i=0; i<4; ++i)
+		vec4_dup(M[i], N[i]);
+}
+LINMATH_H_FUNC void mat4x4_row(vec4 r, mat4x4 const M, int i)
+{
+	int k;
+	for(k=0; k<4; ++k)
+		r[k] = M[k][i];
+}
+LINMATH_H_FUNC void mat4x4_col(vec4 r, mat4x4 const M, int i)
+{
+	int k;
+	for(k=0; k<4; ++k)
+		r[k] = M[i][k];
+}
+LINMATH_H_FUNC void mat4x4_transpose(mat4x4 M, mat4x4 const N)
+{
+    // Note: if M and N are the same, the user has to
+    // explicitly make a copy of M and set it to N.
+	int i, j;
+	for(j=0; j<4; ++j)
+		for(i=0; i<4; ++i)
+			M[i][j] = N[j][i];
+}
+LINMATH_H_FUNC void mat4x4_add(mat4x4 M, mat4x4 const a, mat4x4 const b)
+{
+	int i;
+	for(i=0; i<4; ++i)
+		vec4_add(M[i], a[i], b[i]);
+}
+LINMATH_H_FUNC void mat4x4_sub(mat4x4 M, mat4x4 const a, mat4x4 const b)
+{
+	int i;
+	for(i=0; i<4; ++i)
+		vec4_sub(M[i], a[i], b[i]);
+}
+LINMATH_H_FUNC void mat4x4_scale(mat4x4 M, mat4x4 const a, float k)
+{
+	int i;
+	for(i=0; i<4; ++i)
+		vec4_scale(M[i], a[i], k);
+}
+LINMATH_H_FUNC void mat4x4_scale_aniso(mat4x4 M, mat4x4 const a, float x, float y, float z)
+{
+	vec4_scale(M[0], a[0], x);
+	vec4_scale(M[1], a[1], y);
+	vec4_scale(M[2], a[2], z);
+	vec4_dup(M[3], a[3]);
+}
+LINMATH_H_FUNC void mat4x4_mul(mat4x4 M, mat4x4 const a, mat4x4 const b)
+{
+	mat4x4 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];
+	}
+	mat4x4_dup(M, temp);
+}
+LINMATH_H_FUNC void mat4x4_mul_vec4(vec4 r, mat4x4 const M, vec4 const 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];
+	}
+}
+LINMATH_H_FUNC void mat4x4_translate(mat4x4 T, float x, float y, float z)
+{
+	mat4x4_identity(T);
+	T[3][0] = x;
+	T[3][1] = y;
+	T[3][2] = z;
+}
+LINMATH_H_FUNC void mat4x4_translate_in_place(mat4x4 M, float x, float y, float z)
+{
+	vec4 t = {x, y, z, 0};
+	vec4 r;
+	int i;
+	for (i = 0; i < 4; ++i) {
+		mat4x4_row(r, M, i);
+		M[3][i] += vec4_mul_inner(r, t);
+	}
+}
+LINMATH_H_FUNC void mat4x4_from_vec3_mul_outer(mat4x4 M, vec3 const a, vec3 const 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;
+}
+LINMATH_H_FUNC void mat4x4_rotate(mat4x4 R, mat4x4 const 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);
+		mat4x4 T;
+		mat4x4_from_vec3_mul_outer(T, u, u);
+
+		mat4x4 S = {
+			{    0,  u[2], -u[1], 0},
+			{-u[2],     0,  u[0], 0},
+			{ u[1], -u[0],     0, 0},
+			{    0,     0,     0, 0}
+		};
+		mat4x4_scale(S, S, s);
+
+		mat4x4 C;
+		mat4x4_identity(C);
+		mat4x4_sub(C, C, T);
+
+		mat4x4_scale(C, C, c);
+
+		mat4x4_add(T, T, C);
+		mat4x4_add(T, T, S);
+
+		T[3][3] = 1.f;
+		mat4x4_mul(R, M, T);
+	} else {
+		mat4x4_dup(R, M);
+	}
+}
+LINMATH_H_FUNC void mat4x4_rotate_X(mat4x4 Q, mat4x4 const M, float angle)
+{
+	float s = sinf(angle);
+	float c = cosf(angle);
+	mat4x4 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}
+	};
+	mat4x4_mul(Q, M, R);
+}
+LINMATH_H_FUNC void mat4x4_rotate_Y(mat4x4 Q, mat4x4 const M, float angle)
+{
+	float s = sinf(angle);
+	float c = cosf(angle);
+	mat4x4 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}
+	};
+	mat4x4_mul(Q, M, R);
+}
+LINMATH_H_FUNC void mat4x4_rotate_Z(mat4x4 Q, mat4x4 const M, float angle)
+{
+	float s = sinf(angle);
+	float c = cosf(angle);
+	mat4x4 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}
+	};
+	mat4x4_mul(Q, M, R);
+}
+LINMATH_H_FUNC void mat4x4_invert(mat4x4 T, mat4x4 const 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;
+}
+LINMATH_H_FUNC void mat4x4_orthonormalize(mat4x4 R, mat4x4 const M)
+{
+	mat4x4_dup(R, M);
+	float s = 1.f;
+	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[1], R[1]);
+
+	s = vec3_mul_inner(R[0], R[2]);
+	vec3_scale(h, R[2], s);
+	vec3_sub(R[0], R[0], h);
+
+	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]);
+}
+
+LINMATH_H_FUNC void mat4x4_frustum(mat4x4 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.f*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;
+}
+LINMATH_H_FUNC void mat4x4_ortho(mat4x4 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;
+}
+LINMATH_H_FUNC void mat4x4_perspective(mat4x4 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 / tanf(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;
+}
+LINMATH_H_FUNC void mat4x4_look_at(mat4x4 m, vec3 const eye, vec3 const center, vec3 const 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, center, 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[0][1] =  t[0];
+	m[0][2] = -f[0];
+	m[0][3] =   0.f;
+
+	m[1][0] =  s[1];
+	m[1][1] =  t[1];
+	m[1][2] = -f[1];
+	m[1][3] =   0.f;
+
+	m[2][0] =  s[2];
+	m[2][1] =  t[2];
+	m[2][2] = -f[2];
+	m[2][3] =   0.f;
+
+	m[3][0] =  0.f;
+	m[3][1] =  0.f;
+	m[3][2] =  0.f;
+	m[3][3] =  1.f;
+
+	mat4x4_translate_in_place(m, -eye[0], -eye[1], -eye[2]);
+}
+
+typedef float quat[4];
+#define quat_add vec4_add
+#define quat_sub vec4_sub
+#define quat_norm vec4_norm
+#define quat_scale vec4_scale
+#define quat_mul_inner vec4_mul_inner
+
+LINMATH_H_FUNC void quat_identity(quat q)
+{
+	q[0] = q[1] = q[2] = 0.f;
+	q[3] = 1.f;
+}
+LINMATH_H_FUNC void quat_mul(quat r, quat const p, quat const q)
+{
+	vec3 w, tmp;
+
+	vec3_mul_cross(tmp, p, q);
+	vec3_scale(w, p, q[3]);
+	vec3_add(tmp, tmp, w);
+	vec3_scale(w, q, p[3]);
+	vec3_add(tmp, tmp, w);
+
+	vec3_dup(r, tmp);
+	r[3] = p[3]*q[3] - vec3_mul_inner(p, q);
+}
+LINMATH_H_FUNC void quat_conj(quat r, quat const q)
+{
+	int i;
+	for(i=0; i<3; ++i)
+		r[i] = -q[i];
+	r[3] = q[3];
+}
+LINMATH_H_FUNC void quat_rotate(quat r, float angle, vec3 const axis) {
+    vec3 axis_norm;
+    vec3_norm(axis_norm, axis);
+    float s = sinf(angle / 2);
+    float c = cosf(angle / 2);
+    vec3_scale(r, axis_norm, s);
+    r[3] = c;
+}
+LINMATH_H_FUNC void quat_mul_vec3(vec3 r, quat const q, vec3 const 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;
+	vec3 q_xyz = {q[0], q[1], q[2]};
+	vec3 u = {q[0], q[1], q[2]};
+
+	vec3_mul_cross(t, q_xyz, v);
+	vec3_scale(t, t, 2);
+
+	vec3_mul_cross(u, q_xyz, t);
+	vec3_scale(t, t, q[3]);
+
+	vec3_add(r, v, t);
+	vec3_add(r, r, u);
+}
+LINMATH_H_FUNC void mat4x4_from_quat(mat4x4 M, quat const 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;
+}
+
+LINMATH_H_FUNC void mat4x4o_mul_quat(mat4x4 R, mat4x4 const M, quat const q)
+{
+/*  XXX: The way this is written only works for orthogonal 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[0][3] = M[0][3];
+	R[1][3] = M[1][3];
+	R[2][3] = M[2][3];
+	R[3][3] = M[3][3];  // typically 1.0, but here we make it general
+}
+LINMATH_H_FUNC void quat_from_mat4x4(quat q, mat4x4 const 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);
+}
+
+LINMATH_H_FUNC void mat4x4_arcball(mat4x4 R, mat4x4 const M, vec2 const _a, vec2 const _b, float s)
+{
+	vec2 a; memcpy(a, _a, sizeof(a));
+	vec2 b; memcpy(b, _b, sizeof(b));
+	
+	float z_a = 0.;
+	float z_b = 0.;
+
+	if(vec2_len(a) < 1.) {
+		z_a = sqrtf(1. - vec2_mul_inner(a, a));
+	} else {
+		vec2_norm(a, a);
+	}
+
+	if(vec2_len(b) < 1.) {
+		z_b = sqrtf(1. - vec2_mul_inner(b, b));
+	} else {
+		vec2_norm(b, b);
+	}
+	
+	vec3 a_ = {a[0], a[1], z_a};
+	vec3 b_ = {b[0], b[1], z_b};
+
+	vec3 c_;
+	vec3_mul_cross(c_, a_, b_);
+
+	float const angle = acos(vec3_mul_inner(a_, b_)) * s;
+	mat4x4_rotate(R, M, c_[0], c_[1], c_[2], angle);
+}
+#endif