Let's see now how to apply the conventional technique we have described in the previous chapter: let's make a central perspective scheme which we'll use to draw a room.
First of all let's draw the ground line GL, on which we imagine to stand, and the horizon line HL at the same level of our eyes. These two lines are parallel. The point of view P is on the HL in the middle of the background wall because in this case we are perfectly central, otherwise it could be set on left or on right.
The lines on the roof above our eyes, and the lines on the floor under our eyes flow into P.
Point D on the HL is the one towards which all the lines which form an angle of 45° with the GL (in this case the diagonal line on the floor) flow. Where the segment AD, linking point D to the ground GL, crosses the flight line, the segment BP, linking the ground to the point P, there will be found point C. From this point C raises the dotted line side of the right-angled wallgroun, which develops the background wall.
In order to complete the room, let's draw the tiled floor. Let's transfer on the GL the segments corrensponding to the bases of the square tiles, and from the points corresponding to the edge of the segments let's draw the flight lines converging to point P. Where these converging lines cross the floor diagonal, passing trough points A and D, let's draw the lines parallel to the GL: thus getting the perspective of the tiled floor squared.
In order to create door and windows, let's count some tiles along the side of the room and let's rise the vertical lines. The hight of the corner nearest to the observer will be the reference for the hight of the door itself. Let's link the highest point to the point of view P, and we'll get the frame of the door. Proceed the same way to draw the window.
Now let's rub out the construction lines and you'll get the drawing of the perpective room.