In our project, we are required to do a perspective drawing in the first floor of CFA

For my works, I first found the vanishing point(point C in the above picture) and distance point(point O') in the space, and then extended lines from the vanishing point to pinpoint the position of everything.  For example, the following sketch the vanishing point is close to the center of the drawing. The position of the wall and ceiling are determined by the extended lines from the  vanishing point.(This is a perspective from the second floor)