Measure the length, width and height of the room, which you need to draw. For example, suppose that its height will be equal to 3 m, width 5 m and length 4 m.
Draw on paper a rectangle ABCD. The segments AB and CD is horizontal (width of room), and segments AC and BD vertical (height of the room). The segments BD and CD will divide into 3 and 5 equal parts. In scale they will be equal to 1 m.
Measure and draw a horizon line parallel to segment CD. Usually it is at a height of 1.6 m from the bottom line, i.e. in your case from segment CD. Label the point of intersection of the horizon line with segments AC and BD as H1 and H2. On the horizon, find the center and mark the point E. This is the so-called vanishing point, a point where you focus your gaze.
To get the corners of the room, from the points A, b, C and D draw lines to the vanishing point E.
Cut the CD (the width of the room which is 5 m) had been divided into 5 equal parts. Now from each point of division draw lines to the vanishing point E.
To paint the opposite wall, you're looking at should on your drawing to indicate the depth of the room (this is the length of the room 4 m). To do this, from the point D1 on the segment AC, draw a line to the segment CD, for division 4. Label this intersection as point K.
The intersection of the cut with cut Н1К CE mark point C1. From this point up to the right and draw lines to the intersection of their diagonals AE and DE. From the points two lines that closed the rectangle opposite wall.
So you could easily draw a window and door and interior, located right and left of you, you need to properly scale them in depth. For this you should conduct a parallel horizontal lines from the intersection points of the segment Н1К with the lines that you previously spent each division cut of SD to the vanishing point E. the lines should intersect with the lines EC and ED (the corners of the room).
On the wall to the right of you, draw the window. For example, suppose it is at a distance of 1 m from the edge of the room where you stand. From the point of H2 swipe cut to a point lying on the segment CD.
On the segment BD (the height of the room) designate a point of the window height from floor to window sill. From this longing to vanishing point E draw a line. In the place of its intersection with cut Н2К supply point and then from it draw a vertical line, which will be the height of the window to scale.
To correctly indicate on your drawing the height, draw a line from the vanishing point E of the segment BD at the height that you need (i.e. from the sill to the top of the window).
The width of the window, i.e. its depth in the term defined by the lines that you used to spend parallel to segment CD. On the same principle are drawn in the door and all of the furnishings.