Description
1. Overview
In this assignment you will implement a simple graphics package using the
OpenGL graphics library. Using inheritance, geometric objects will be displayed in
a window. The lab workstations all run X11 so there is no problem there. When you
log into the server remotely, be sure to specify the -X option, as in :
ssh -X username@unix.ucsc.edu
Before you log into the server make sure you have an X11 client running on your
own workstation.
2. Program Specification
The program is presented in the form of a Unix man(1) page.
NAME
gdraw—drawing program displaying objects in a window
SYNOPSIS
gdraw [ options] [filename]
OPTIONS
All options are recognized by getopt(3).
-@ flags
The flags specified are passed to the debugging macro. Debug output is
printed to the standard error.
-w width
The initial width of the window. Default : 640.
-h height
The initial height of the window. Default : 480.
OPERANDS
Commands are read from the file whose name is given as an operand. If no
filename is given, commands are read from the standard input.
COMMANDS
When the program begins,awindow is created for displaying information,
which consists of text and geometric objects of various kinds. The project proceeds in two parts :
(a) Shapes are defined in terms of their sizes (length, width, or vertices).
(b) Objects are drawn in the window by drawing commands, after which
they may be altered by keyboard commands.
Sizes, lengths, widths, and coordinates are all floating point numbers, and
measure pixels.
Colors may be specified by name using one of the names in the file rgb.txt, or
by their hexadecimal values in the form 0xRRGGBB, where RR, GG, and BB are the
red, green, and blue components specified as two hexadecimal numbers in the
range 00 to FF.
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The define command makes a record of the definition of an shape and makes
it available later for a draw command. The draw command creates an object in
the screen’s object list, to be displayed when the program starts.
The following commands are recognized. Each command is on a line by itself
and terminates with the newline character. If the last character on a line is a
backslash (\), the command is continued onto the next line.
# …
A comment line is ignored, as are empty lines and lines consisting only of
white space.
define name text font words …
A text object is created by concatenating all of the words together, each
separated from the next by spaces. The font is any of the seven GLUT
bitmap fonts :
• Fixed-8×13
• Fixed-9×15
• Helvetica-10
• Helvetica-12
• Helvetica-18
• Times-Roman-10
• Times-Roman-24
define name ellipse width height
An ellipse is specified with the major and minor diameters specified.
When drawn, the drawing coordinate is the center.
define name circle diameter
A circle is just an ellipse whose length and width are equal.
define name polygon x0 y0 x1 y1 x2 y2 …
A polygon is specified with the number of vertices being equal to the
number of (x, y) coordinates given. The polygon must be convex (each
interior angle less than 180 degrees). The convexity is not verified by the
program, so the appearance of a non-convex polygon is undefined. The
center of the polygon is at (x, y), i.e., at the average of all the x coordinates and the average of the y coordinates. After computing the average,
it is subtracted from each of the vertices to normalize them. For example, if the vertices are specified as shown in the left side of the diagram,
they are normalized to that shown on the right side, so that (x, y)
changes from (. 5,. 5) to (0, 0).
(0,0) (1 ,0)
(0,1) (1 ,1)
(. 5,. 5)
(−.5, −.5) (+.5, −.5)
(−.5, +.5) (+.5, +.5)
(0,0)
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define name rectangle width height
A rectangle with the given width and height is defined with strictly horizontal and vertical lines with the given thickness. When drawn, the
drawing coordinates will be the center.
define name square width
A square is a rectangle with equal width and height.
define name diamond width height
A diamond’s width is from the leftmost to rightmost point and its height
is from topmost to bottommost height. The draw command specifies its
center.
define name triangle x0 y0 x1 y1 x2 y2
A triangle is just another name for a polygon.
define name right_triangle width height
Define a right triangle with width the horizontal bar extending to the
right and height the vertical bar.
define name isosceles width height
The width specifies the width of the base, and the height specifies the
perpendicular distance from the base to the apex.
define name equilateral width
Makes an isosceles triangle that is also equilateral.
border color thickness
Specifies the thickness in pixels of the border surrounding the selected
object, and its color. Defaults : red, 4.
moveby pixels
The move parameter indicates how many pixels an object moves when
directed by one keystroke. Default : 4.
draw color name xcenter ycenter
Draws an object with the center at (x, y) using the color specified.
KEYBOARD INPUT
Once the input file is finished, the keyboard is used to command the movements of the objects. The following keystrokes control the program :
‘Q’, ‘q’, Escape Close the window.
‘H’, ‘h’, Left Arrow Move the selected object left.
‘J’, ‘j’, Down Arrow Move the selected object down.
‘K’, ‘k’, Up Arrow Move the selected object up.
‘L’, ‘l’, Right Arrow Move the selected object right.
‘N’, ‘n’, Space, Tab Set the selection to the next object.
‘P’, ‘p’, Backspace Set the selection to the previous object.
‘0’ … ‘9’ Set the selection to objects 0 through 9, respectively.
F1 … F12 Set the slection to objects 1 through 12, respectively.
An object is always displayed using the coordinates of the center. If an object
is moved off the window, it appears at the other end of the window. That is, if
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the x or y coordinate exceeds the width (height) of the windor, it is set to 0. If
it becomes negative, it is set to the width (height). The selected object is
always surrounded by a border to make it visible. For objects 0 through 12,
the object’s number is displayed in the center of the object.
EXIT STATUS
0 No errors were detected.
1 Errors were detected and messages printed to the standard error.
3. Code
OpenGL and GLUT will be used to display the window. See the short example programs in the misc/ subdirectory. Starter code is in the code/ subdirectory. For documentation, Google using the terms ‘‘OpenGL’’ and/or ‘‘GLUT’’ and the name of the
function, then look for results naming the web pages in www.opengl.org/documentation.
4. What to Submit
Submit all C++ source files and the Makefile. If you are doing pair programming,
also submit the PARTNER file.
