mat4 lookAt(vec4 pos, vec4 dir) {
vec4 f = dir;
normalizevec4(&f);
vec4 u = {{0, 1, 0, 0}};
vec4 s = crossvec4(f, u);
normalizevec4(&s);
u = crossvec4(s, f);
mat4 out = IDENTITY_MATRIX;
out.m[0] = s.x;
out.m[4] = s.y;
out.m[8] = s.z;
out.m[1] = u.x;
out.m[5] = u.y;
out.m[9] = u.z;
out.m[2] = -f.x;
out.m[6] = -f.y;
out.m[10] = -f.z;
out.m[12] = -dotvec4(s, pos);
out.m[13] = -dotvec4(u, pos);
out.m[14] = dotvec4(f, pos);
return out;
}
float lengthvec4(vec4 v) {
return sqrt(dotvec4(v, v));
}
