I guess this is more conceptual, and not very game programming related, but okay. I have a quantity which is represented by a unit vector in a cvector class, which has an x, y, z, and magnitude values and then can normalize itself. In my situation they represent acceleration due to gravitation. I don't understand how I can add a vector in the form aB + cD = xY with a, b being scaler magnitudes, B and D being directed unit vectors, and xY being sum.