I am too new to grasp the function writing concept in POV.
the first step to matrix control is axis_rotation
#declare a=1.0;
#declare b=0.0;
#declare c=0.0;
#declare d=0.0;
#declare e=1.0;
#declare f=0.0;
#declare g=0.0;
#declare h=0.0;
#declare i=1.0;

#declare X=0.0;
#declare Y=0.0;
#declare Z=0.0;

#declare A=<a,b,c>;
#declare B=<d,e,f>;
#declare C=<g,h,i>;

#declare axis_rotation = function(r, z, y) {
// y * z * r //this only to see if pov accepts defined funtion parameters.
// it does.
// how to parse or tokenize a vector?

// C code is:
// r is radians (r,axis[3],point[3])

 /*
 double mag, s, c;
 double x, y, z, xx, yy, zz, xy, yz, zx, xs, ys, zs, one_c;
 s = sin(r);
 c = cos(r);
 mag = VLEN(axis);
     // prevent divide by 0 error and normalize axis
 if (mag == 0.0) mag = 1.0;
 x = axis[0] / mag;
 y = axis[1] / mag;
 z = axis[2] / mag;

 xx = x * x;
 yy = y * y;
 zz = z * z;
 xy = x * y;
 yz = y * z;
 zx = z * x;
 xs = x * s;
 ys = y * s;
 zs = z * s;
 one_c = 1.0 - c;

 x = point[0] * ((one_c * xx) + c);
 y = point[0] * ((one_c * xy) - zs);
 z = point[0] * ((one_c * zx) + ys);

 x += point[1] * ((one_c * xy) + zs);
 y += point[1] * ((one_c * yy) + c);
 z += point[1] * ((one_c * yz) - xs);

 x += point[2] * ((one_c * zx) - ys);
 y += point[2] * ((one_c * yz) + xs);
 z += point[2] * ((one_c * zz) + c);

 point[0] = x;
 point[1] = y;
 point[2] = z;
 */

//and usage should be: vector = axis_rotation(r,A,B)

}

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