Representation of vector and multiplication.

There are two ways to represent of vector.

row vector and column vector.

[x y z] is a row vector

[x]
[y]
[z]

is a column vector.

When we multiple a vector with matrix, should be careful.

For instance we want to apply matrix A, B then C in order and there is a vector 'v'
depending on the representation of vector, we use it differently.

if the v is a row vector then we should use vABC.
if the v is a column vector then we should use CBAv.

Many books and game engine uses differently. so you should be careful when you use it.

1. Check representation of vector.
2. Check an order of matrix and then apply it to the vector carefully.