Drawings aid for making drawings in perspective

A drawing aid for use in making drawings in perspective, having at least one transparent chart unit with proper angle, distance and height scales needed for making drawings in perspective. A drawback of known drawing aids of this kind is that they have been provided with scales which are exceedingly difficult to read and that, in the course of drawing, auxiliary lines are invariably produced which clutter up the drawing. The chart unit of the invention has a first chart corresponding to the horizontal plane and marked with radial angles and arcs corresponding to distance, a second chart corresponding to the vertical plane and marked with radial angles and vertical lines corresponding to distance, and an image plane chart corresponding to the image plane, the latter usually serving as a drawing substrate with coordinates consistent with the angle scales of the first and second charts.

BACKGROUND OF THE INVENTION 
The object of the present invention is a drawing aid for producing 
perspective drawings, which consists of at least one transparent chart 
unit carrying the proper angle, distance and height scales to be used when 
drawing figures in perspective. 
A drawing aid for drawing figures in perspective is disclosed e.g. in the 
U.S. Pat. No. 3,492,727. The drawback of the known aid of this kind is 
that, having numerous scales, it is very difficult to read, and in drawing 
the figure auxiliary lines have to be traced, which tend to confuse the 
drawing and hamper the drawing of detailed parts. Another drawback of the 
known aids of this kind is that the locations of the vanishing points are 
predetermined and therefore the viewing direction is always the same in 
all perspective figures. 
SUMMARY OF THE INVENTION 
The object of the present invention is to eliminate the above drawbacks and 
to provide a drawing aid to a new type which is quick and easy to operate. 
The drawing aid of the invention is characterized in that the chart unit 
has: a diagram inscribed with radial angles corresponding to the 
horizontal plane and arcs corresponding to distance; a diagram 
corresponding to the vertical plane inscribed with radial angles and 
vertical lines corresponding to distance; and an image plane diagram 
corresponding to the image plane, the latter normally serving as a drawing 
substrate and having coordinates consistent with the angle scales of the 
first two diagrams. By means of the invention it is possible first and 
foremost to position the point to be processed at a desired distance and 
under a desired angle to the left or right in relation to the viewing 
direction. By using the chart, the requisite coordinates are found and the 
corresponding points are plotted on the image plane, whereafter by 
connecting these points the perspective drawing can be directly created 
without need of auxiliary lines whatsoever which would clutter up the 
drawing. 
A preferred embodiment of the present invention is characterized in that 
the image plane is a cross-ruled chart which can be mounted on the drawing 
board and overlayed with a sheet of transparent drawing paper. Several 
such charts in different sizes may be provided, thus enabling perspective 
drawings in desired size to be obtained simply by replacing the image 
plane chart with another. The creation of perspective figures in very 
large size is thus also rendered possible. The size of the drawing may 
subsequently be changed by photographic processing, and the drawing may be 
combined with photographs. The charts of the invention are also applicable 
in examining perspective drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The drawing aid consists of charts comprising a horizontal plane chart V, a 
vertical plane chart P and an image plane chart K. The chart V is marked 
with radial angles from zero to 35.degree. to the left and from zero to 
35.degree. to the right, and with arcs corresponding to distance, the 
distances being marked from zero to 40 meters, for instance. The chart P 
is marked, consistent with the vertical plane, with vertical lines 
corresponding to radial angles upwards from zero to 25.degree. and 
downwards from zero to 25.degree., referred to the horizontal plane, and 
with vertical lines marking the distance. The chart P also carries a scale 
from zero to 40 meters. The cross-ruling of the image plane chart K is 
consistent with the horizontal and vertical angle scales of the charts V 
and P, respectively. The V and P charts should be as transparent as 
possible. The drawing substrate K may be either transparent or opaque. The 
point O of the chart V has to be placed to coincide with the desired 
viewing point and the line OS, with the desired viewing direction. The 
distances are marked on the distance scale according to the map scale that 
was enployed in preparing the figure, general layout, site plan, etc. used 
in the drawing process. Drawing of the perspective figure proceeds as 
follows: The location, on the chart K, of the point to be processed is 
determined in that by means of the chart V the angle, to the right or to 
the left of the viewing directions OS, corresponding to the direction of 
this point, is first found. The location of the point is marked, on the 
basis of the number of degrees defining said angle, on a sheet of 
transparent material, such as paper, attached upon the image plane chart 
K. Next, the distance of the point is read on the scale V with the aid of 
the distance scale. The chart P is placed upon a section, elevation or 
other vertical projection drawing so that the line corresponding to the 
viewing direction is horizontal on the viewing height consistent with the 
main scale. The chart P is moved in accordance with the distance found on 
the distance scale of the chart V in the direction indicated by the arrow 
1, so that the viewing point O will have the proper distance from the 
corner of the building or equivalent, which is being processed. 
Thereafter, for instance the direction angles of the lowest and highest 
points of the corner upwards or downwards from the viewing direction OP-SP 
are read from the chart P. The locations of the points on the image plane 
chart K will be determined by the direction angle thus obtained, with the 
aid of the numbers of degrees. The figure will thus emerge point by point, 
or vertical edge by vertical edge, on the transparent paper mounted over 
the drawing substrate K. The size of the figure is predetermined by the 
size of the image plane chart K. The scales of the charts V and P may be 
different as to the distance scales, but their map scale must be the same 
as that of the underlying drawings. Image plane charts K may be provided 
in a plurality of different sizes, whereby the size of the figure can be 
selected according to circumstances. As a rule it is advisable to draw the 
figure as large as possible and reduce it photographically to its final 
size. The drawing accuracy can be increased by increasing the line density 
of the charts.