1. Starting to draw dealing with Windows which libraries? clipping
program organization
color
geometric primitives
curved objects

2. May be needed for some Windows Ok for all – check with class.
In main, replace glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); with glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); At the end of display, replace glFlush(); with glutSwapBuffers(); note glut vs gl

3. First edition includes
# include <iostream>
# ifdef __APPLE__
# include <GLUT/glut.h>
# else
# include <GL/glut.h>
# endif

4. Second edition includes
#ifdef __APPLE__ # include <GL/glew.h> # include <GL/freeglut.h> # include <OpenGL/glext.h> #else # include <GL/glext.h> #pragma comment(lib, "glew32.lib") #endif

5. 2nd edition (openGL4.3)
requires other modifications of code we won't be doing yet – stick to first edition examples. Also for homework – I will not be using glew or freeglut.

6. square. cpp Add it to your project and get it running
square.cpp Add it to your project and get it running. Make a triangle as below.
glBegin(GL_POLYGON);
glVertex3f(20.0, 20.0,0);
glVertex3f(80.0, 20.0, 0.0);
glVertex3f(80.0, 80.0, 0.0);
glEnd();
square2.cpp part YYY partially outside the box in z direction.
part ZZZ partially outside the box

7. square.cpp with clipping Modify the z value of the first vertex
glBegin(GL_POLYGON);
glVertex3f(20.0, 20.0,10);
glVertex3f(80.0, 20.0, 0.0);
glVertex3f(80.0, 80.0, 0.0);
glEnd();
square2.cpp part YYY partially outside the box in z direction.
part ZZZ partially outside the box

8. square.cpp with clipping
glBegin(GL_POLYGON);
glVertex3f(20.0, 20.0,10);
glVertex3f(80.0, 20.0, 0.0);
glVertex3f(80.0, 80.0, 0.0);
glEnd();
square2.cpp part YYY partially outside the box in z direction.
part ZZZ partially outside the box

9. Understanding the program organization: main
// Main routine: defines window properties, creates window,
// registers callback routines and begins processing.
int main(int argc, char **argv) {
// Initialize GLUT.
glutInit(&argc, argv);
// Set display mode as single-buffered and RGB color.
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
// Set OpenGL window size.
glutInitWindowSize(500, 500);
// Set position of OpenGL window upper-left corner.
glutInitWindowPosition(100, 100);
// Create OpenGL window with title.
glutCreateWindow("square.cpp");
notice glut prefix

10. Modify the window title – square.cpp with modifications or something.

11. main (cont) // Initialize. setup(); // Register display routine.
glutDisplayFunc(drawScene);
// Register reshape routine.
glutReshapeFunc(resize);
// Register keyboard routine.
glutKeyboardFunc(keyInput);
// Begin processing.
glutMainLoop();
return 0; }
note functions without glut prefix

12. Add print statements to see which functions are being called.
Add these lines at the top of the appropriate functions, then run. Resize window – what happens?
cout << "In drawScene" << endl;
cout << "In resize" << endl;
cout << "In setup" << endl;
cout << "In keyInput" << endl;

13. void setup(void);
// Initialization routine.
void setup(void) {
// Set background (or clearing) color.
glClearColor(1.0, 1.0, 1.0, 0.0); }

14. void drawScene(void);
// Drawing (display) routine.
void drawScene(void) {
// Clear screen to background color.
glClear(GL_COLOR_BUFFER_BIT);
// Set foreground (or drawing) color.
glColor3f(0.0, 0.0, 0.0);

15. void drawScene(void); (cont)
// Draw a polygon with specified vertices.
glBegin(GL_POLYGON);
glVertex3f(20.0, 20.0, 0.0);
glVertex3f(80.0, 20.0, 0.0);
glVertex3f(80.0, 80.0, 0.0);
glVertex3f(20.0, 80.0, 0.0);
glEnd();
// Flush created objects to the screen, i.e.,
force rendering.
glFlush(); }

16. other functions
Deal with someone changing the size
of the window.
void resize(int w, int h);
Keyboard input processing routine.
void keyInput(unsigned char key,
int x, int y);

17. Color Sensitive Cones
Credit: Ron Nave

18. Color in OpenGL glColor3f(red, green, blue) arguments between 0 and 1

19. state variables glColor3f(red,green,blue); drawing color
glClearColor(red, green, blue, 0.0);
background color
glClear(GL_COLOR_BUFFER_BIT);
Sets every pixel to background color.
Remove and see what happens!

20. Modify square: Another rectangle of a different color.
Immediate mode graphics -
objects are drawn and forgotten!
squareV2.cpp part 1
first do part 0 – old square

21. Modify square: Different vertices different colors
Colors bound to vertices of a primitive
are interpolated throughout the interior.
squareV2.cpp part 2
Discuss importance to shading

22. OpenGL Geometric Primitives

23. More OpenGL Geometric Primitives

24. Try some of these primitives in square.cpp
May want to add:
glPointSize(3.0);
to make the points bigger
glLineWidth(4.0):
to make the lines thicker

25. filled in or outlines glPolygonMode(face, mode) face can be GL_FRONT
GL_BACK
GL_FRONT_AND_BACK
mode can be
GL_FILL
GL_LINE
GL_POINT

26. Try several triangles, various ways.
Can do
GL_TRIANGLES
GL_TRIANGLE_STRIP
To see triangles can use
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
To see filled in and edges, draw twice:
filled in, change color, then outlines.
squareV2.cpp part 3, triangle strips.
squareV2.cpp part 4 added to part 3.
Notice Part 4 is above part 3.
Part 5 is fan
Switch from FRONT_AND_BACK to two statements, one FRONT, one BACK
to see if seeing front or back!

27. Beware of convexity!
Try convexity Example.

28. Curved Objects Run the program circle.cpp. Observe
instructions in comment and console screen
global variables
new version of color: glColor3ub
use of rand()
glutPostRedisplay in keyInput
circle.cpp add as source to SquareForClass2

29. parametric equation of circle