1. Lab 3
Geometric Drawing
Lab 3
Geometric Drawing

2.  General format of the programs  Geometric Drawing Primitives  Drawing shapes
 Drawing a point  Drawing line

3. Format
Description
#include < windows.h >
call Library glut And all libraries
#include <GL/glut.h>
needed by the programmer
Global variables
Global variables
void draw(void)
Graphic data functions }
Graphic data functions {
void main()
main function {
the function be called in the }
main

4. glutCreateWindow(char *name);
Create a window under the name OpenGL
Example: glutCreateWindow("OpenGL");

5. glutInitWindowSize( int width, int height)
Control the height and width of the drawing
window
Example: glutInitWindowSize(400,400);

6. glutInitWindowPosition( int x, int y);
Determine the place of drawing window on the computer screen. It is not a requirement of
writing this function because the window appear
in the default point of origin. The point of origin always be in the upper left corner of the
computer screen
Example: glutInitWindowPosition(0,0);

7. GlutInitDisplayMode(int mode);
Determine the display mode of the window  Mode -> GLUT_RGB, GLUT_RGBA
Indicate that the window will be used to display system colors  Mode -> GLUT_SINGLE
Indicate that we will open a window with one memory, Always used with this mode
glFlush();
 Mode -> GLUT_DOUBLE
Indicate that we will open a window with two memory, Is used when we have animation Always used with this mode glSwapBuffers();
 Mode ->GLUT_DEPTH
Indicate that we will open a window with memory depth (Three- dimensional programming )
 The default value
Mode -> GLUT_RGBA l GLUT_SINGLE

8. glClearColor(red, green, blue, alpa); -> RGBA
glClearColor(red, green, blue); -> RGB
Determine the background color

9. R G B
190 63
218
190/255
63/255
218/255
0.74
0.24
0.85
Extract a color from any painting program such as paint or photoshop programs, then use either:
glColor3f(0.74, 0.24, 0.85); RGB or
glColor3ub(190, 63, 218); RGB

10. glClear(mask);
mask -> The type of memory used for the Clear  mask ->
GL_COLOR_BUFFER_BIT (This always used) GL_DEPTH_BUFFER_BIT
Example : glClear(GL_COLOR_BUFFER_BIT);

11. glutDisplayFunc(Graphic data functions );
used to see the Graphic data functions
Example: glutDisplayFunc(draw);
glutMainLoop();
Does not display windows painted so we have to
put at the end of the program

12. gluOrtho2D (GLdouble left , GLdouble right , GLdouble bottom ,GLdouble top);
 Left -> xmin
 Right -> xmax  Bottom -> ymin  Top -> ymax

13. glOrtho (GLdouble left , GLdouble right ,
GLdouble bottom , GLdouble top , GLdouble zNear , GLdouble zFar) ;
 Left -> xmin
 Right -> xmax  Bottom -> ymin  Top -> ymax  Near -> zNear  Far -> zFar

14. #include <windows.h> #include <GL/glut.h>
void draw(void) {
glClear(GL_COLOR_BUFFER_BIT);
glFlush(); }
void main() {
glutInitWindowSize(200,200);
glutInitDisplayMode(GLUT_RGB);
glutCreateWindow("Empty Screen");
glOrtho(0.0, 100.0, 0.0, 100.0, 0.0, 1.0);
glClearColor(0.95, 0.90, 0.85, 0.0);
glutDisplayFunc(draw);
glutMainLoop(); }

15. Any shape is drawn through the points By the function
glVertex* ();
(……..) 2
d,f,i
x,y 3
d,f,i
x,y,z 4
d,f,i
x,y,z,t

16. Points of any shape limited between two functions
glBegin(mode);
glVertex* (…); glEnd();

17. After understanding how to specify vertices, you still need to tell OpenGL to create a set of points, a line, or a polygon from those vertices. To do this, you bracket each set of vertices between a call to glBegin() and a call to glEnd(). The argument passed to glBegin() mode determines what sort of geometric primitive is constructed from the vertices.

18. Mode
Point
GL_POINTS
Line
GL_LINES
GL_LINE_STRIP GL_LINE_LOOP
Triangle
GL_TRIANGLES
GL_TRIANGLE_STRIP
GL_TRIANGLE_FAN
Quads
GL_QUADS
GL_QUAD_STRIP
Polygon
GL_POLYGON

20. we will learn how to draw a point x=50 , y=50
glBegin(GL_POINTS);
glVertex2i (50,50);
glEnd();
 glColor3f(red, green, blue);
Used for coloring any point or shape  glPointSize(size);
Control the size of the point

21. #include <windows.h>
#include <GL/glut.h> void draw(void) {
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.4, 0.4, 0.6); glPointSize(10);
glBegin(GL_POINTS); glVertex2i(50,50); glEnd();
glFlush(); }
void main() {
glutInitWindowSize(160,160);
glutInitDisplayMode(GLUT_RGB);
glutCreateWindow("Point");
glOrtho(0.0, 100.0, 0.0, 100.0, 0.0 glClearColor(0.95, 0.90, 0.85, 0.0) glutDisplayFunc(draw);
glutMainLoop(); }

22. #include <windows.h> #include <GL/glut.h>
void draw(void) {
glClear(GL_COLOR_BUFFER_BIT);
glPointSize(4);
glBegin(GL_POINTS); glColor3f(0, 0, 1); glVertex2i(40,40); glEnd();
glPointSize(10);
glBegin(GL_POINTS);
glColor3f(0.8, 0.5, 0.0); glVertex2i(50,50); glEnd();
glPointSize(20);
glBegin(GL_POINTS);
glColor3f(0.5, 0.0, 0.2); glVertex2i(60,60); glEnd();
glFlush(); }
void main() { ……………. }

23. glBegin(mode);
…… glVertex* (…);
glEnd();
•Mode to draw Line GL_LINES
GL_LINE_STRIP GL_LINE_LOOP

24. GL_LINES
pairs of vertices interpreted as individual line
segments
glBegin (GL_LINES);
glVertex2i (p1);
glVertex2i (p2); glEnd();

25. glBegin (GL_LINES); glVertex2i (V0);
glVertex2i (V2); glVertex2i (V3);
glVertex2i (V4);
glVertex2i (V5); glVertex2i (V6); glVertex2i (V7); glEnd();

26. GL_LINE_STRIP
series of connected line segments
glBegin (GL_LINE_STRIP);
glVertex2i (p1);
glVertex2i (p2);
glVertex2i (p3); glVertex2i (p4);
glVertex2i (p5);
glVertex2i (p6); glEnd();

27. GL_LINE_LOOP
same as above, with a segment added between last and first vertices
glBegin (GL_LINE_LOOP); glVertex2i (p1);
glVertex2i (p2);
glVertex2i (p3); glVertex2i (p4);
glVertex2i (p5);
glVertex2i (p6); glEnd();

28. Void glLineWidth(GLfloat Width);  Line Color
glColor3f(red , green , blue);  Line Style
Void glLineStipple(GLint factor , GLushort pattern);

30. How can we write this function in the program
glEnable(GL_LINE_STIPPLE)
glLineStipple(factor , pattern); glDisable(GL_LINE_STIPPLE)
Example:
glEnable(GL_LINE_STIPPLE) glLineStipple(1 , 0XFF); glDisable(GL_LINE_STIPPLE)

31. // Font Size
glLineWidth (3.0);
// Line Styles Enable Function
glEnable (GL_LINE_STIPPLE); // Font Color
glColor3f (0.0, 0.0, 0.0);
// Line Style
glLineStipple (1, 0x1111); // Line Drawing Function glBegin(GL_LINES); glVertex2f (0, 0); glVertex2f (30, 0); glEnd();

32. Write c++ program to draw lines like the following window.