1. OPENGL

2. OpenGL OpenGL resources: www.opengl.org
The Red Book,
Manual pages,

3. OpenGL OpenGL core library OpenGL Utility (GLU)
OpenGL Utility Toolkit (GLUT)
Header files:
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

4. #include <GL/glut.h> // (or others, depending on the system in use) void init (void) { glClearColor (1.0, 1.0, 1.0, 0.0); // Set display-window color to white. glMatrixMode (GL_PROJECTION); // Set projection parameters. gluOrtho2D (0.0, 200.0, 0.0, 150.0); } void lineSegment (void) { glClear (GL_COLOR_BUFFER_BIT); // Clear display window. glColor3f (0.0, 0.0, 1.0); // Set line segment color to blue. glBegin (GL_LINES); glVertex2i (180, 15); // Specify line-segment geometry. glVertex2i (10, 145); glEnd ( ); glFlush ( ); // Process all OpenGL routines as quickly as possible. void main (int argc, char** argv) { glutInit (&argc, argv); // Initialize GLUT. glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); // Set display mode. glutInitWindowPosition (50, 100); // Set top-left display-window position. glutInitWindowSize (400, 300); // Set display-window width and height. glutCreateWindow ("An Example OpenGL Program"); // Create display window. init ( ); // Execute initialization procedure. glutDisplayFunc (lineSegment); // Send graphics to display window. glutMainLoop ( ); // Display everything and wait.
OpenGL

5. OpenGL Point Functions glVertex*( ); * : 2, 3, 4 i (integer) s (short)
f (float)
d (double)
Ex:
glBegin(GL_POINTS);
glVertex2i(50, 100);
glEnd();
Ex:
int p1[ ]={50, 100};
glBegin(GL_POINTS);
glVertex2iv(p1);
glEnd();

6. OpenGL Line Functions GL_LINES GL_LINE_STRIP GL_LINE_LOOP Ex:
glBegin(GL_LINES);
glVertex2iv(p1);
glVertex2iv(p2);
glEnd();

7. OpenGL
glBegin(GL_LINES); GL_LINES GL_LINE_STRIP glVertex2iv(p1); glVertex2iv(p2); glVertex2iv(p3); glVertex2iv(p4); glVertex2iv(p5); glEnd(); GL_LINE_LOOP p3 p3 p5 p1 p1 p2 p4 p2 p4 p3 p5 p1 p2 p4

8. OpenGL Ex: glBegin(GL_POINTS); GL_POINTS glVertex2iv(p1);
glEnd();
glPointSize(size);
size: 1,2,…
Ex:
glPointSize(2.0); // 2x2 pixels p3 p5 p1 p2 p4

9. OpenGL Polygon Functions glRect*(x1, y1, x2, y2); Ex: Ex: i (integer)
s (short)
f (float)
d (double)
v (vector)
Ex:
glRecti(200, 100, 50, 250);
Ex:
int v1[ ]={200, 100};
int v2[ ]={50, 250};
glRectiv(v1, v2);
(50, 250)
(200, 100)

10. OpenGL Ex: GL_POLYGON glBegin (GL_POLYGON); glVertex2iv(p1);
glEnd(); p6 p5 p1 p4 p2 p3
GL_POLYGON

11. OpenGL Ex: GL_TRIANGLES glBegin (GL_TRIANGLES); glVertex2iv(p1);
glEnd(); p6 p5 p1 p4 p2 p3
GL_TRIANGLES

12. OpenGL Ex: GL_TRIANGLES GL_TRIANGLE_STRIP GL_TRIANGLE_FAN
glBegin (GL_TRIANGLES);
glVertex2iv(p1);
glVertex2iv(p2);
glVertex2iv(p6);
glVertex2iv(p3);
glVertex2iv(p4);
glVertex2iv(p5);
glEnd(); p6 p5 p1 p4 p2 p3
GL_TRIANGLES p6 p6 p5 p5 p1 p4 p1 p4 p2 p3 p2 p3
GL_TRIANGLE_STRIP
GL_TRIANGLE_FAN

13. OpenGL Ex: GL_QUADS GL_QUAD_STRIP glBegin (GL_QUADS); glVertex2iv(p1);
glEnd(); p8 p1 p4 p5 p7 p6 p3 p2
GL_QUADS
GL_QUAD_STRIP

14. OpenGL RGB colors Red Green Blue Color Black 1 Cyan Magenta Yellow
Black 1
Cyan
Magenta
Yellow
White

15. OpenGL Color Functions
glClearColor(r, g, b, a); 0.0 ≤ r, g, b, a ≤ 1.0
specifies the color for color buffers
glClear(GL_COLOR_BUFFER_BIT);
applies the clear color to the color buffers
Ex:
glClearColor(1.0, 1.0, 1.0, 0.0); // White
glColor(GL_COLOR_BUFFER_BIT);

16. OpenGL Color Functions glColor3f(r, g, b); 0.0 ≤ r, g, b ≤ 1.0
Ex:
glColor3f(1.0, 0.0, 0.0); // Red
glColor3ub(r, g, b); 0 ≤ r, g, b ≤ 255
glColor3ub(255, 0, 0); // Red

17. OpenGL Reshape Function glutReshapeFunc(func); Ex:
glutReshapeFunc(my_reshape_func);

18. OpenGL – Transformations
Matrix Operations
glMatrixMode routine:
Projection mode (GL_PROJECTION)
Modelview mode (GL_MODELVIEW)
Texture mode
Color mode

19. OpenGL – Transformations
Modelview Mode
glMatrixMode(GL_MODELVIEW);
designates 4x4 modelview matrix as the current matrix.
glLoadIdentity();
assigns the identity matrix to the current matrix.

20. OpenGL – Transformations
Translate
glTranslatef (tx, ty, tz);
Scale
glScalef (sx, sy, sz);
Rotate
glRotatef (theta, vx, vy, vz);

21. OpenGL I Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue
glRecti(0,0,80,40);
glFlush ( );
Modelview Matrix I

22. OpenGL I I.T Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue
glRecti(0,0,80,40);
glFlush ( );
Modelview Matrix I
glColor3f (1.0, 0.0, 0.0); // red
glTranslatef(10.0, 10.0, 0.0);
glRecti(0,0,80,40);
glFlush ( );
I.T

23. OpenGL I I.T I.T.S Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue
glRecti(0,0,80,40);
glFlush ( );
Modelview Matrix I
glColor3f (1.0, 0.0, 0.0); // red
glTranslatef(10.0, 10.0, 0.0);
glRecti(0,0,80,40);
glFlush ( );
I.T
glColor3f (1.0, 0.0, 0.0); // red
glScalef(2.0, 2.0, 0.0);
glRecti(0,0,80,40);
glFlush ( );
I.T.S

24. OpenGL I I.T I.T.S I.T.S.R Modelview Matrix
glColor3f (0.0, 0.0, 1.0); // blue
glRecti(0,0,80,40);
glFlush ( );
Modelview Matrix I
glColor3f (1.0, 0.0, 0.0); // red
glTranslatef(10.0, 10.0, 0.0);
glRecti(0,0,80,40);
glFlush ( );
I.T
glColor3f (1.0, 0.0, 0.0); // red
glScalef(2.0, 2.0, 0.0);
glRecti(0,0,80,40);
glFlush ( );
I.T.S
glColor3f (0.0, 1.0, 0.0); // green
glRotatef(20.0, 0.0, 0.0, 1.0);
glRecti(0,0,80,40);
glFlush ( );
I.T.S.R

25. OpenGL – Transformations
Matrix Stack
glPushMatrix ();
glPopMatrix ();

26. OpenGL I I.T I.T.S I.T.R Modelview Matrix Stack
glColor3f (0.0, 0.0, 1.0); // blue
glRecti(0,0,80,40);
glFlush ( ); I
glColor3f (1.0, 0.0, 0.0); // red
glTranslatef(10.0, 10.0, 0.0);
glRecti(0,0,80,40);
glPushMatrix();
glFlush ( );
I.T
I.T
glColor3f (1.0, 0.0, 0.0); // red
glScalef(2.0, 2.0, 0.0);
glRecti(0,0,80,40);
glFlush ( );
I.T.S
I.T
glColor3f (0.0, 1.0, 0.0); // green
glPopMatrix();
glRotatef(20.0, 0.0, 0.0, 1.0);
glRecti(0,0,80,40);
glFlush ( );
I.T.R

27. OpenGL Ex: ROBOT transform robot glPushMatrix() transform head
draw head
glPopMatrix()
transform body
transform left_arm
draw left_arm
transform right_arm
draw right_arm
draw body
Ex: ROBOT

28. OpenGL – 2D Viewing Clipping Window Viewport Function
gluOrtho2D (xwmin, xwmax, ywmin, ywmax); float or double
Viewport Function
glViewport (xvmin, yvmin, vpWidth, vpHeight); integer
Window
(xwmax, ywmax)
Viewport
vpHeight
vpWidth
(xvmin, yvmin)
(xwmin, ywmin)

29. OpenGL – 2D Viewing Create Display Window Display Window Mode
glutInit (&argc, &argv)
glutInitWindowPosition (xTopLeft, yTopLeft)
glutInitWindowSize (width, height)
windowID=glutCreateWindow (“title”)
glutDestroyWindow (windowID)
Display Window Mode
glutInitDisplayMode (mode)
Ex:
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

30. OpenGL – 2D Viewing Display Functions glutDisplayFunction (dFunc)
dFunc (callback function) describes what is to be displayed in the current window
glutPostRedisplay ()
Indicates that the contents of the current display window should be renewed
glutIdleFunc (iFunc)
iFunc is executed when there are no other events for the system to process
glutMainLoop ()

31. OpenGL – 3D Viewing Projection glMatrixMode (GL_PROJECTION)
Orthogonal Projection
gluOrtho (xwmin, xwmax, ywmin, ywmax, dnear, dfar)
Perspective Projection
gluPerspective (theta, aspect, dnear, dfar)
theta: field-of-view angle (00 – 1800)
aspect: aspect ratio of the clipping window (width/height)
dnear, dfar: positions of the near and far planes (must have positive values)
glFrustum (xwmin, xwmax, ywmin, ywmax, dnear, dfar)
if xwmin = -xwmax and ywmin = -ywmax then symmetric view volume

32. OpenGL – 3D Viewing glMatrixMode (GL_MODELVIEW)
gluLookAt (x0, y0, z0, xref, yref, zref, Vx, Vy, Vz)
Designates the origin of the viewing reference frame as,
the world coordinate position P0=(x0, y0, z0)
the reference position Pref=(xref, yref, zref) and
the viewup vector V=(Vx, Vy, Vz)
double-precision, floating-point values xw yw zw xv yv zv V P0 N
Pref

33. OpenGL – 3D Viewing
gluLookAt (x0, y0, z0, xref, yref, zref, Vx, Vy, Vz)
Default parameters are:
P0=(0,0,0)
Pref=(0,0,-1)
V=(0,1,0) xw yw zw xv yv zv V P0
Pref

34. OpenGL float eye_x, eye_y, eye_z; void init (void) {
glClearColor (1.0, 1.0, 1.0, 0.0); // Set display-window color to white.
glMatrixMode (GL_PROJECTION); // Set projection parameters.
glLoadIdentity();
gluPerspective(80.0, 1.0, 50.0, 500.0); // degree, aspect, near, far
glMatrixMode (GL_MODELVIEW);
eye_x = eye_y = eye_z = 60;
gluLookAt(eye_x, eye_y, eye_z, 0,0,0, 0,1,0); // eye, look-at, view-up }
void main (int argc, char** argv) {
glutInit (&argc, argv); // Initialize GLUT.
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); // Set display mode.
glutInitWindowPosition (50, 500); // Set top-left display-window position.
glutInitWindowSize (400, 300); // Set display-window width and height.
glutCreateWindow ("An Example OpenGL Program"); // Create display window.
glViewport (0, 0, 400, 300);
init ( ); // Execute initialization procedure.
glutDisplayFunc (my_objects); // Send graphics to display window.
glutReshapeFunc(reshape);
glutKeyboardFunc(keybrd);
glutMainLoop ( ); // Display everything and wait.

35. OpenGL Functions Cube glutSolidCube (size) glutWireCube (size) Cone
glutSolidCone (base_radius, height, slices, stacks)
glutWireCone (base_radius, height, slices, stacks)
Sphere
glutSolidSphere (radius, slices, stacks)
glutWireSphere (radius, slices, stacks)
Teapot
glutSolidTeapot (size)
glutWireTeapot (size)
Torus
glutSolidTorus (inner_radius, outer_radius, nsides, rings)
glutWireTorus (inner_radius, outer_radius, nsides, rings)

36. OpenGL Functions Tetrahedron glutSolidTetrahedron ()
glutWireTetrahedron ()
4 sided
Octahedron
glutSolidOctahedron ()
glutWireOctahedron ()
8 sided
Dodecahedron
glutSolidDodecahedron ()
glutWireDodecahedron ()
12 sided
Icosahedron
glutSolidIcosahedron ()
glutWireIcosahedron ()
20 sided

37. OpenGL glPolygonMode(GL_FRONT_AND BACK, GL_LINE) glEnable (GL_FOG)
displays both visible and hidden edges
glEnable (GL_FOG)
glFogi (GL_FOG_MODE, GL_LINEAR)
generates fog effect. Uses depth cueing.
glEnable (GL_CULL_FACE)
glDisable (GL_CULL_FACE)
glCullFace (mode)
used for backface removal
GL_BACK (default), GL_FRONT (if inside a building), GL_FRONT_AND_BACK

38. OpenGL glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH)
initializes GLUT, requests a depth buffer and a frame buffer
glClear (GL_DEPTH_BUFFER_BIT)
initially depth buffer has the background color. It must be cleared every time before displaying a new frame.
glEnable (GL_DEPTH_TEST)
glDisable (GL_DEPTH_TEST)
to activate depth buffer routines
glClearDepth (maxDept)
to set maxDepth to another value (0.0 – 1.0)
glDepthRange (nearNormDept, farNormDept)
to adjust normalization values (defaults: near- 0.0, far- 1.0)

39. Diffuse and Specular Lightings
I = Idiff + Ispec
= ka Ia + kd Il (N.L) + ks Il (N.H)ns

40. OpenGL GLfloat pos[ ] = {x, y, z, w}
(x, y, z): position
w: type 1.0 – local (positional light)
0.0 – distant (directional light)
glLightfv(GL_LIGHT1, GL_POSITION, pos)
GL_POSITION sets the light position and type
glEnable (GL_LIGHT1)
glDisable (GL_LIGHT1)

41. OpenGL GLfloat color[ ] = {r, g, b, a}
(r, g, b): RGB color (I)
a: alpha (used only if color blending routines are active)
glLightfv(GL_LIGHT1, GL_AMBIENT, color)
glLightfv(GL_LIGHT1, GL_DIFFUSE, color)
glLightfv(GL_LIGHT1, GL_SPECULAR, color)
GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR set the light color

42. OpenGL GLfloat dir[ ] = {x, y, z}
if light source is not spotlight
fl,angatten = if Vobj.Vlight=cos a < cos ql
(Vobj . Vlight )al otherwise
OpenGL
GLfloat dir[ ] = {x, y, z}
(x, y, z): direction vector Vlight
default direction (0.0, 0.0, -1.0)
glLightfv(GL_LIGHT2, GL_SPOT_DIRECTION, dir)
glLightfv(GL_LIGHT2, GL_SPOT_CUTOFF, c)
c: cut off angle θ (0o-90o)
glLightfv(GL_LIGHT2, GL_SPOT_EXPONENT, e)
e: exponent value for angular intensity attenuation (0-128)
Vlight
Vobj ql a

43. OpenGL GLfloat ka[ ] = {r, g, b, a} GLfloat kd[ ] = {r, g, b, a}
GLfloat ks[ ] = {r, g, b, a}
(r, g, b): RGB color (k)
a: alpha
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, ka)
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, kd)
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, ks)
glMaterialfv(GL_FRONT_AND_BACK, GL_SHININESS, s)
s: specular reflection exponent (0-128)
GLfloat emissioncolor[ ] = {r, g, b, a}
glMaterialfv(GL_FRONT, GL_EMISSION, emissioncolor)

44. OpenGL glColor4f(R, G, B, A) glEnable (GL_BLEND) glDisable (GL_BLEND)
A: alpha parameter
1.0 – transparent
0.0 - opaque
glEnable (GL_BLEND)
glDisable (GL_BLEND)