The document discusses setting up 3D scenes in OpenGL using matrices. It states that to see a 3D scene, you need to set up the camera, projection, and world matrix. The camera and projection matrices are singletons that apply to all objects, while the world matrix is set separately for each object. It explains the camera matrix sets the camera position and orientation, while the projection matrix handles perspective vs orthographic projections. The world matrix transforms individual objects by scaling, rotating, and translating them. It provides an example of drawing objects by setting their world matrix before rendering.

1. Mohammad Shaker
mohammadshaker.com
@ZGTRShaker
2015
OpenGL Graphics
L02–TRANSFORMATIONS

2. Matrices in OpenGL, 4x4
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3. RULE

4. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:

5. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA

6. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA
PROJECTION

7. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA
PROJECTION
WORLDMATRIX

8. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

9. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

10. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

11. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

12. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

13. Camera (View) Matrix

14. Camera (View) Matrix
void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ,
GLdouble centerX, GLdouble centerY, GLdouble centerZ,
GLdouble upX, GLdouble upY, GLdouble upZ);

15. Camera (View) Matrix
void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ,
GLdouble centerX, GLdouble centerY, GLdouble centerZ,
GLdouble upX, GLdouble upY, GLdouble upZ);

16. Camera (View) Matrix
void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ,
GLdouble centerX, GLdouble centerY, GLdouble centerZ,
GLdouble upX, GLdouble upY, GLdouble upZ);

17. Camera (View) Matrix
void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ,
GLdouble centerX, GLdouble centerY, GLdouble centerZ,
GLdouble upX, GLdouble upY, GLdouble upZ);

18. Camera Movement

19. Set the View (Camera) Matrix
• For example, in ReSizeGLScene method
GLvoid ReSizeGLScene(GLsizei width, GLsizei height)
{
if (height==0) { height=1; }
glViewport(0,0,width,height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt( 0.0, 0.0, 5.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0 );
}

20. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

21. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

22. Projection Matrix

23. Projection

24. Projection Matrices

25. Perspective Projection

26. Orthographic Projection

27. Projection Matrices
The Difference?!

28. Projection Matrices
The Difference?!perspective

29. Projection Matrices
The Difference?!perspective orthographic

30. Projection Matrices
Realistic?perspective orthographic

31. Projection Matrices
Realistic?perspective orthographic

32. Projection Matrices
Architecture?perspective orthographic

33. Projection Matrices
Architecture?perspective orthographic

34. Projection Matrices
Usability?perspective orthographic

35. Projection Matrices
Usability?perspective orthographic

36. Perspective Projection
• void gluPerspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)
• void glFrustum(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top,
GLdouble znear, GLdouble zfar);

37. Near and Far Clipping Planes
• Wrong Near and Far clipping planes can cause problems.

38. Orthographic Projection
• void gluOrtho(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top,
GLdouble near, GLdouble far)

39. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

40. RULE
TOSEEA3DSCENEYOUSHOULDSETUP:
CAMERA(Singleton,forallobjects)
PROJECTION(Singleton,forallobjects)
WORLDMATRIX(Foreachobjectseparately)

41. World Matrix
Each Object in 3D Has Its Own World Matrix

42. World Matrix

43. World Matrix
• Example
• Let’s assume that the coordinates of the triangle vertices are as follows:

44. World Matrix
• Example
• To translate 40 units over the y axis’s positive direction,all you need to do is to add 40
toeach y position, and you have the new coordinates for the vertices:

45. World Matrix

46. Many Transformation?

47. Many Transformation?
Always Use I.S.R.O.T

48. Identity
Scale
Rotate
Orbit
Translate

49. World Matrices
• glScalef(x, y, z);
• glTranslatef(x, y, z);
• glRotatef(angle, x, y, z);

50. World Matrices
• glScalef(x, y, z);
• glTranslatef(x, y, z);
• glRotatef(angle, x, y, z);
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51. World Matrices
• glLoadIdentity();

52. Where to put the projection, camera and world
matrices in code?

53. Let’s see the
OpenGL Program Structure

54. OpenGL Program Structure
• Application Structure
– Configure and open window
– Initialize OpenGL state
– Register input callback functions
• render
• resize
• input: keyboard, mouse, etc.
– Enter event processing loop

55. OpenGL Program Structure
• Application Structure
– Configure and open window
– Initialize OpenGL state
– Register input callback functions
• render
• resize
• input: keyboard, mouse, etc.
– Enter event processing loop
void main( int argc, char** argv )
{
int mode = GLUT_RGB|GLUT_DOUBLE;
glutInitDisplayMode( mode );
glutCreateWindow( argv[0] );
init();
glutDisplayFunc( display );
glutReshapeFunc( resize );
glutKeyboardFunc( key );
glutIdleFunc( idle );
glutMainLoop();
}

56. OpenGL Program Structure
• Application Structure
– Configure and open window
– Initialize OpenGL state
– Register input callback functions
• render
• resize
• input: keyboard, mouse, etc.
– Enter event processing loop

57. OpenGL Program Structure
• Application Structure
– Configure and open window
– Initialize OpenGL state
– Register input callback functions
• render
• resize
• input: keyboard, mouse, etc.
– Enter event processing loop
void main( int argc, char** argv )
{
int mode = GLUT_RGB|GLUT_DOUBLE;
glutInitDisplayMode( mode );
glutCreateWindow( argv[0] );
init();
glutDisplayFunc( display );
glutReshapeFunc( resize );
glutKeyboardFunc( key );
glutIdleFunc( idle );
glutMainLoop();
}

58. Now back to
“Where to put the projection, camera and world matrices in code?”

59. Set the Projection and Camera Matrices
• Initialize Projection and Camera in ReSizeGLScene() or init() methods
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt( 0.0, 0.0, 5.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0 );
GLvoid init()

60. Set the Projection and Camera Matrices
• And the world matrix of each object should be set on the DrawGLScene() method
// Draw a triangle
// Draw a square
// a polygon
// another triangle
// ..etc
GLvoid DrawGLScene()
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt( 0.0, 0.0, 5.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0 );
GLvoid init()

61. NEW
RULE Remember,Remember?
OpenGLprogrammingisstate-machinebased

62. NEW
RULE Remember,Remember?
OpenGLprogrammingisstate-machinebased
ChangingStateWithoutyouknowingyou’re
changingthestateisaverybigdeal/Problem

63. NEW
RULE Remember,Remember?
OpenGLprogrammingisstate-machinebased
ChangingStateWithoutyouknowingyou’re
changingthestateisaverybigdeal/Problem

64. ChangingStateWithoutyouknowingyou’re
changingthestateisaverybigdeal/Problem
EXAMPLE

65. ChangingStateWithoutyouknowingyou’re
changingthestateisaverybigdeal/Problem
EXAMPLE
PrimitiveandTransformation

66. First, init()
• First, we init the Projection and Camera in ReSizeGLScene() or init() methods
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt( 0.0, 0.0, 5.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0 );
GLvoid init()

67. Second, DrawGLScene()
• Second, Then we draw everything we want in DrawGLScene() method.
GLvoid DrawGLScene()
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt( 0.0, 0.0, 5.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0 );
GLvoid init()

68. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

69. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

70. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

71. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

72. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

73. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

74. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
GLvoid DrawGLScene()

75. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}

76. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}

77. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}

78. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}

79. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}

80. Primitive and Transformation Example
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}

81. What would you do
if you have 100 objects?!

82. Matrix Stack

83. Matrix Stack
glPushMatrix();
// A Body Transformation
glPopMatrix();

84. Using Matrix Stack
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); // Reset The View
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
return TRUE; // Keep Going
}
We left our code like this:

85. Using Matrix Stack
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Now, it will look like this:

86. Using Matrix Stack
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Now, it will look like this:

87. Using Matrix Stack
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Now, it will look like this:
Applying I.S.R.O.T
Applying I.S.R.O.T

88. Using Matrix Stack
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
The result is exactly the same

89. Adding Some Colors

90. Using Matrix Stack
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Our code is like this:

91. Using Matrix Stack
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glColor3f(1.0f,0.0f,0.0f); // Set The Color To Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glColor3f(0.0f,1.0f,0.0f); // Set The Color To Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glColor3f(0.0f,0.0f,1.0f); // Set The Color To Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();

92. Applying Some Animation
(Transformation)

93. // Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glColor3f(1.0f,0.0f,0.0f); // Set The Color To Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glColor3f(0.0f,1.0f,0.0f); // Set The Color To Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glColor3f(0.0f,0.0f,1.0f); // Set The Color To Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
We have this code:

94. // Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glColor3f(1.0f,0.0f,0.0f); // Set The Color To Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glColor3f(0.0f,1.0f,0.0f); // Set The Color To Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glColor3f(0.0f,0.0f,1.0f); // Set The Color To Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units And Into The Screen 6.0
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
We have this code:

95. rtri+=0.2f;
rquad-=0.15f;
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glRotatef(rtri, 0, 1, 0); // Rotate around the Y axis with the rtri parameter
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glColor3f(1.0f,0.0f,0.0f); // Set The Color To Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glColor3f(0.0f,1.0f,0.0f); // Set The Color To Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glColor3f(0.0f,0.0f,1.0f); // Set The Color To Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units
glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Change it to this:
Applying I.S.R.O.T

96. rtri+=0.2f;
rquad-=0.15f;
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glRotatef(rtri, 0, 1, 0); // Rotate around the Y axis with the rtri parameter
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glColor3f(1.0f,0.0f,0.0f); // Set The Color To Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glColor3f(0.0f,1.0f,0.0f); // Set The Color To Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glColor3f(0.0f,0.0f,1.0f); // Set The Color To Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units
glRotatef(rquad, 1,0, 0); // Rotate around the X axis with the rquad parameter
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Change it to this:
Applying I.S.R.O.T
Applying I.S.R.O.T

97. rtri+=0.2f;
rquad-=0.15f;
// Clear The Screen And The Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0
glRotatef(rtri, 0, 1, 0); // Rotate around the Y axis with the rtri parameter
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glColor3f(1.0f,0.0f,0.0f); // Set The Color To Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glColor3f(0.0f,1.0f,0.0f); // Set The Color To Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glColor3f(0.0f,0.0f,1.0f); // Set The Color To Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd(); // Finished Drawing The Triangle
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f); // Move Right 1.5 Units
glRotatef(rquad, 1,0, 0); // Rotate around the X axis with the rquad parameter
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd(); // Done Drawing The Quad
glPopMatrix();
Change it to this:

98. Let’s Clean the Code a Bit..
(You can find it in L02-Sol01)

99. Transformation Example
void DrawTriangle()
{
rtri+=0.2f;
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glRotatef(rtri, 0, 1, 0);
glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f( 0.0f, 1.0f, 0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();
}
void DrawQuad()
{
rquad-=0.15f;
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f)
glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();
}
int DrawGLScene(GLvoid)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
DrawTriangle();
DrawQuad();
return TRUE;
}
GLvoid DrawGLScene()

100. Transformation Example
void DrawTriangle()
{
rtri+=0.2f;
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glRotatef(rtri, 0, 1, 0);
glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f( 0.0f, 1.0f, 0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();
}
void DrawQuad()
{
rquad-=0.15f;
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f)
glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();
}
int DrawGLScene(GLvoid)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
DrawTriangle();
DrawQuad();
return TRUE;
}
GLvoid DrawGLScene()

101. Transformation Example
void DrawTriangle()
{
rtri+=0.2f;
glPushMatrix();
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glRotatef(rtri, 0, 1, 0);
glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f( 0.0f, 1.0f, 0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();
}
void DrawQuad()
{
rquad-=0.15f;
glPushMatrix();
glLoadIdentity();
glTranslatef(1.5f,0.0f,-6.0f)
glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();
}
int DrawGLScene(GLvoid)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
DrawTriangle();
DrawQuad();
return TRUE;
}
GLvoid DrawGLScene()

102. So let’s wrap up!
Transformation Pipeline

103. OpenGL Architecture
Display
List
Polynomial
Evaluator
Per Vertex
Operations &
Primitive
Assembly
Rasterization
Per Fragment
Operations
Frame
Buffer
Texture
Memory
CPU
Pixel
Operations

104. OpenGL Architecture
Display
List
Polynomial
Evaluator
Per Vertex
Operations &
Primitive
Assembly
Rasterization
Per Fragment
Operations
Frame
Buffer
Texture
Memory
CPU
Pixel
Operations
We are here,
Let’s zoom in!

105. v
e
r
t
e
x
Modelview
Matrix
Projection
Matrix
Perspective
Division
Viewport
Transform
Modelview
Modelview
Projection
l
l
l
object eye clip normalized
device
window
• other calculations here
– material and color
– shade model (flat)
– polygon rendering mode
– polygon culling
– clipping
Transformation Pipeline

106. v
e
r
t
e
x
Modelview
Matrix
Projection
Matrix
Perspective
Division
Viewport
Transform
Modelview
Modelview
Projection
l
l
l
object eye clip normalized
device
window
• other calculations here
– material and color
– shade model (flat)
– polygon rendering mode
– polygon culling
– clipping
Transformation Pipeline

107. v
e
r
t
e
x
Modelview
Matrix
Projection
Matrix
Perspective
Division
Viewport
Transform
Modelview
Modelview
Projection
l
l
l
object eye clip normalized
device
window
• other calculations here
– material and color
– shade model (flat)
– polygon rendering mode
– polygon culling
– clipping
Transformation Pipeline

108. v
e
r
t
e
x
Modelview
Matrix
Projection
Matrix
Perspective
Division
Viewport
Transform
Modelview
Modelview
Projection
l
l
l
object eye clip normalized
device
window
• other calculations here
– material and color
– shade model (flat)
– polygon rendering mode
– polygon culling
– clipping
Transformation Pipeline

109. v
e
r
t
e
x
Modelview
Matrix
Projection
Matrix
Perspective
Division
Viewport
Transform
Modelview
Modelview
Projection
l
l
l
object eye clip normalized
device
window
• other calculations here
– material and color
– shade model (flat)
– polygon rendering mode
– polygon culling
– clipping
Transformation Pipeline