sub method
Implementation
Vector4 sub(Vector4 v, Vector4? w) {
if (w != null) {
print('three.Vector4: .sub() now only accepts one argument. Use .subVectors( a, b ) instead.');
return subVectors(v, w);
}
x -= v.x;
y -= v.y;
z -= v.z;
this.w -= v.w;
return this;
}