27
Example
For each map (slide) for which conversion is desired, the
following constants and reference points should be computed and stored in a table. (The computations show below are for Slide 79, The
World, 105 W to 124 E):
Scaling Factor (k)
Determine the screen distance between two parallels of longitude (via cursor and cursor coordinate feature). If the distance between two parallels is 205„ units and their separation is 30° (.52 radians) then:
205 *U38 133 ,_, unit .52 .52 = <"° radians Slide Constant (c)
This constant represents the distance from the bottom of the screen (y = 0) to the equator. If the equator is shown on the map, then the distance can be measured directly via the cursor; other- wise, it must be computed from (1) by solving for k. For Slide 79 the distance was measured and found to be:
c = 5538. Fixed Reference Points
(\>>V
The fixed reference point is usually chosen in the center region of the map to reduce distortion by optical irregularities.
In this case, the reference point was selected as (30°N, 30°E) with the corresponding (via cursor) screen coordinates of (1110,777)g.
Hence:
A = 30°
o
X • 1110Q P 8
28
Conversion Example
Assume coordinates 45 N, 90 W are to be converted:
Then A =-90"
<t> = 45°
-1.57 radians
x = 256 (-1.57 -.524) + 1110g - 61g
y = 256 In tan(1.177) + 553g
= 256 (.884) + 553g =• H15g.
Consequently, the desired screen coordinates are (61,1115)
8'
POLAR STEREOGRAPHIC (Northern Hemisphere) The transformation is given by:
7T 0
x = k tan (— - •*) cos (A+or) + c^
y = k tan (— --) sin (A+a) + c, 4 2
(2)
where A
k
cl'C2'a
longitude of point whose conversion is desired;
latitude of point whose conversion is desired;
scaling factor (to be computed);
constants (to be computed or measured).
29
Example
The computations shown below were performed for Slide 88, Entire Northern Hemisphere.
Scaling Factor (k)
This factor must be computed by solving either component equation of (2) for k. A fixed point must be selected to provide corresponding values of (X , </>) and (x,y) . For this slide, k was found to be 553g.
Constants
The pair (c^,c2) represents the screen coordinates corresponding to the North Pole; in this case (754,761)3 as measured by cursor.
The constant a represents the angular displacement of the central meridian from the screen x-axis, measured in a counter- clockwise direction. (This constant was found to be 15° for all polar stereographic slides in magazine zero).
Conversion Example
Assume coordinates 30N, 30E to be converted:
x = 553g tan (-^ - 15°) cos (30° + 15°) + 754g = 1200g
= 553g tan(-Zj - 15°) sin (30° + 15°) + 76 lg = 1205g
REMARK
While the set of constants needs to be computed only once for each slide, differences in optics and slide mounting between BR-90 consoles necessitate the computation of separate constants for distinct display consoles.
30
APPENDIX C GRAPHIC MANIPULATION
In modern applications of interactive graphic displays, it is common to perform various operations on individual components
(subpictures) of an existing display string (frame). The general objective of such operations is the construction of a new picture from an existing frame with a minimum of effort and high degree of versatility. Typical examples of such procedures include:
a) Construction of complex pictures from simple components (i.e., construction of electrical network diagrams from basic subpictures showing resistors, capacitors, etc.);
b) Changing sections of an existing display frame to indicate occurrence of a dynamic process (i.e., change in disposition of forces with respect to a background map);
c) Enlarging a display or selected components (zooming or scissoring).
In addition to sophisticated buffer management, various mathematical display string manipulation techniques are required to perform operations of this category. All of these mathematical functions result in transformation of the CRT screen coordinates associated with the vectors or points constituting a frame or sub- frame. Two categories of elementary transformation are presented with the objective of stimulating interest for application to a command and control environment13.
RIGID TRANSFORMATIONS Preliminary Assumptions
a) The three dimensional Cartesian coordinate system will be chosen as follows. The CRT screen will be the xy plane, as is the usual fashion, and the z axis will be normal to the screen toward the observer. It should be noted that this coordinate system is right handed.
13 These techniques have been employed for BR-90 demonstrations at the AFICCS Support Facility.
31
b) The object to be displayed will be assumed to exist in 3-dimensional space with some predefined configuration (i.e., we are given a set of points (x,y,z) which define the object). For our purposes, the z coordinates will be less than zero, since the object to be displayed will be considered to be 'behind' the screen.
c) Once we have chosen some point (xQ,y0,z0) as a basis of projection (here z0 is also less than zero), we can project a point
(x,y,z) from the base point (xo.yg.Zo) onto the screen yielding some (x*,y',0). The ordered pair (x',y*) will be the desired CRT
screen coordinate.
Rigid Motions
The following formulas govern rigid motion (translation, rotation) in space:
I) Translation of a point (x,y,z) by a displacement (<$x, <5y, 6 z)
x' ;
X «JXY' Y + <5Y
z' :
i
. Z
<5z i
(1)
II) Rotation of a point about a coordinate axis (all rotations are assumed to be clockwise):
a) Rotation of a point (x,y,z) by an angle a about the x axis:
r,l
1 0 01 X I
Jr
s 0cos a sina
Y iZ' 0
—sina cos a
Z J
, _
1(2)
32
b) Rotation of a point (x,y,z) by an angle /3
For display purposes, in light of assumption (1), the equation of the plane of projection will simply by z =0. The above ideas were implemented in a BR-90 program which displays a projection of a 3-dimensional cube which can be translated or rotated. A table of sines was stored in the BR-90 core for use in equations (2) -
(4). The cosine was computed by the fact that cos $ • sin (90 - $) . Translation was considered along the x and y axes only. Also, the point of projection was taken to be at an infinite distance away on the z axis.
DATA SCALING
This process is the mapping of one rectangular area onto
another rectangular area. Data scaling is required for the conver- sion of any numerically oriented input for particular CRT displays.
Immediate applications are:
33
a) Super-imposition of background map data with CRT data; and b) Zooming (expansion of selected portions of CRT screen to
the full screen).
The following notation will be used for the data scaling function:
a) Let A be the rectangle to be projected, while B is the rectangle onto which images of rectangle A are projected;
b) Let (x1,y.) be the coordinates of lower left corner of B;
c) Let (x?,y_) be the coordinates of upper right corner of B;
d) Let (u1,v.) be the coordinates of lower left corner of A;
e) Let (u-,v„) be the coordinates of upper right corner of A; and f) Let (u,v) be the point of A which is to be projected onto
B at point (x,y).
(x2,y2) ' - 1
(x,y)'
i
](U2'v2) (X, ,yi)
(u,v)'
B(UjtVj)
A
_
CRT Screen
34
The following linear functions can be used for data scaling:
(u - up (x2 - xx)
x = —7 r + x, ; and
(u2 ~ ul)
(v - v^ . (y2 - yx)
Y = (v2 "Vl> + Yl
Zooming
Zooming provides for the expansion of selected portions of the CRT screen to the full screen size in such a manner as to preserve angles (conformal) and relative distances. The above equations are applicable and for the BR-90 reduce to:
17778 U - Ul x = *
17778 Iv - v y =
where d = max ( | u. - u. , v2 ~ vl "^
35
BIBLIOGRAPHY
Bunker Ramo Corporation, Programming Reference Manual For Message Console AN/FYQ-45, April 1967.
C. Christensen and E.N. Pinson, Multi-Function Graphics For A Large Computer System, Proc. of Nat. Conf. of ACM, 1967, pp. 355-365.
H. Corbin and W. Frank, Display Oriented Computer Usage System, Thompson Book Co., 1966.
J.C. Gray, Compound Data Structure For Computer Aided Design; A Survey, Proc. of Nat. Conf. of ACM, 1967, pp. 355-365.
F. Gruenberger, ed., Computer Graphics, Thompson Book Co., Washington, D.C. , 1967.
IBM, Programmer Procedures Manual For Console Interface Programs (CIP), November 1967.
IBM, Computer Program Specifications For Console Interface Programs (CIP) November 1967.
E.L. Jacks, A Laboratory For the Study of Graphical Maa-Machine Communication, AFIPS Conf. Proc, Vol. 26, FJCC 1964, pp. 343-350.
H.E. Kulsrud, A General Purpose Graphic Laaguage, Comm, of the ACM, April 1968, pp. 247-254.
M.H. Levin, An Introduction to Computer Graphic Terminals, IEEE Proc., Vol. 55, September 1967, pp. 1544-1552.
The MITRE Corporation, IBM, Bunker-Ramo, The Operation of the AFICCS Display System in the IBM 1410 Data Processing System, Technical Memorandum #1, December 1966.
The MITRE Corporation, BR-90 Assembly Program - BRASS, MTR-597, March 1968.
The MITRE Corporation, The AN/FYQ-45/38 at the AFICCS Support Center, WP-2150, March 1968.
The MITRE Corporation, Alternatives For Achieving a Large Panel Display Capability Within AFICCS, MTR-702, April 1968.
36
BIBLIOGRAPHY (Concluded)
The MITRE Corporation, Data Flow Improvements — Design Specifications For AFICCS Serial File Manipulators, MTR-711, May 1968.
The MITRE Corporation, A Way To Time Share Within AFICCS, WP-2241, May 1968.
The MITRE Corporation, A Review of the Operational Aspects of the AFICCS Display System, MTR-727, June 1968.
The MITRE Corporation, Display Software Techniques for AFICCS, MTR-754, August 1968.
The MITRE Corporation, The AFICCS BR-90 Display Software: A Description and Extension of N-mode Program Concepts, WP-2535, January 1969.
The MITRE Corporation, Dynamic Data Integration; Design Specifica- tions for AFICCS File Manipulative Functions, MTR-573, January 1968.
The MITRE Corporation, Classification of Console Displays and Their Functional Applications, MTR-814, February 1969.
The MITRE Corporation, A BR-90 Display Experiment in Distributed Processing, WP-2576, February 1969.
The MITRE Corporation, A BR-90 Operating System, MTR-857, May 1969.
I.E. Sutherland, SKETCHPAD — A Man-Machine Graphical Communication System, AFIPS Conf. Proc. , Vol. 23, SJCC 1963, pp. 329-346.
I.E. Sutherland, Computer Graphics, Datamation, May 1966, pp. 22-27.
A.H. Vorhaus, General Purpose Display System, Datamation, July 1966, pp. 59-64.
37
Security Classification
DOCUMENT CONTROL DATA -R&D
(Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classified) I . ORIGINATING ACTIVITY (Corporate author)
The MITRE Corporation
AFICCS Display Software Recommendations
4. DESCRIPTIVE NOTES (Type of report and inclusive dates)
N/A
5- AUTHORISI ffirsf name, middle initial, last name)
Otto W. Beebe
8a. CONTRACT OR GRANT NO.
AF19(628)-68-C-0365
This document has been approved for public release and sale; its distribution is unlimited.
II. SUPPLEMENTARY NOTES
N/A
12. SPONSORING MILITARY ACTIVITY
Director of Planning and Technology, Electronic Systems Division, AF Systems Command, USAF, L. G. Hanscom Field, Bedford. Massachusetts
13. ABSTRACT
This document summarizes a study of the AFICCS display system. Currently available AFICCS display features are reviewed and deficiencies, or lack of existence, are noted. Recommendations for improvements are segregated into two categories; near-term and long-range.
DD
1 NO V 65 FORM1473
Security Classification
Security Classification
KEY wo RDS
Computer Graphics Display Software AFICCS
Time Sharing Buffer Management Graphics Applications
Security Classification