setAxisAngle method
Set to a rotation of angle radians about the axis (ax, ay, az).
A zero axis gives the identity.
Implementation
void setAxisAngle(double ax, double ay, double az, double angle) {
final len = math.sqrt(ax * ax + ay * ay + az * az);
if (len < 1e-12) {
setIdentity();
return;
}
final half = angle * 0.5;
final s = math.sin(half) / len;
x = ax * s;
y = ay * s;
z = az * s;
w = math.cos(half);
}