Learning Event 3:
DEFINE PICTURE PLANE, STATION POINT AND VANISHING POINT
1. The station point for the plan view was located as described earlier.
As was stated, the station point is the observer's eye.
station point for the side view is actually the same station point as that
shown for the top view. Thus, it is the same horizontal distance from the
cube, but its elevation shows the height of the station point above the
level of the cube.
The picture plane in the side view is also the same
distance from the cube as in the top view, and the ground line in this view,
on which the picture plane rests, defines the ground line of the picture
plane in the perspective drawing.
2. Notice that the vanishing point and center of vision in this drawing are
located directly above the station point in the perspective drawing and on
the same line with the station point for the side view of the cube. This
line is the eye level line. It is also the horizon line for the drawing.
The intersection point of a projector from a corner of the cube in the top
view with the projector from the same corner in the side view locates the
corner in the perspective drawing.
3. The vanishing point defines the point at which all lines perpendicular
to the picture plane in the perspective drawing converge.
The fact that
there is only one vanishing point in this type of perspective drawing gives
it its name. It is also called parallel perspective because the front face
of the object is parallel to the picture plane.
4. In parallel perspective drawings, the center of vision is not
necessarily centered on the object. It may fall to one side or the other as
shown in Figure 1-5. When the front face is parallel to the picture plane
and the center of vision is at one side of the drawing, there will be
distortion. Actually, the drawing becomes an oblique projection which may
be know as fake perspective and is not a true perspective drawing. Notice
that in order to make such drawing, the object must be considered as resting
with its front face against the picture plane.
If this were not so,
converging projection lines from the corners of the front face would alter
its appearance so that it would no longer appear to be parallel with the
picture plane. In fact, as you will see, it would then become a two-point,
rather than a one-point, perspective drawing.