1. Development of Interactive 3D Virtual World Applications
Lab exercises by
Assoc. Prof. Dr. Emiliyan Petkov

2. Accents
Virtual world – a computer simulation of a real environment which contains real objects
Practical exercises on how to create 3D worlds, import them in a OpenGL application and manipulate cameras and 3D models
Low-level graphics programming lessons (OpenGL)
3D world creation – Blender
Development of an interactive application – Code::Blocks (C++ IDE)
Using a graphics system – OpenGL
Free, cross platform and open source products

3. Lessons Part I – Basics OpenGL GS OpenGL libraries Main functions
Structure of an OpenGL app
Interactivity
OpenGL and Blender:
Lights
Materials
Cameras
Part II – Advanced
Virtual World Development – Blender
X3DLoader library
Creating interactive OpenGL application using X3DLoader library

4. Basics of OpenGL
OpenGL (Open Graphics Library) – cross-platform, high performance graphics, by Khronos Group
GLU and GLUT
Under MS Windows we need:
gl.h, libopengl32.a, opengl32.dll
glu.h, libglu32.a, glu32.dll
glut.h, libglut32.a, glut32.dll
Creating models
10 graphics primitives
glBegin( GL_POLYGON );
glVertex3f( 0.0, 0.5, 0.0 );
glVertex3f( 0.75, -0.5, 0.0 );
glVertex3f( -0.75, -0.5, 0.0 );
glEnd();

5. GLUT main functions
void glutInit(int *argcp, char **argv); - used to initialize the GLUT library
void glutInitWindowPosition(int x, int y); - sets the initial window position
void glutInitWindowSize(int width, int height); - sets the initial window size
void glutInitDisplayMode(unsigned int mode); - sets the initial display mode
int glutCreateWindow(char *name); - creates a top-level window
void glutDisplayFunc(void (*func)(void)); -  sets the display callback for the current window
void glutMainLoop(void); - enters the GLUT event processing loop

6. GLUT 3D Models void glutWireCube(GLdouble size)
void glutSolidCube(GLdouble size)
void glutWireSphere(GLdouble radius, GLint slices, GLint stacks)
void glutSolidSphere(GLdouble radius, GLint slices, GLint stacks)
and more

7. GLUT management of events
void glutReshapeFunc(void (*func)(int width, int height)); - sets the reshape callback for the current window
void glutKeyboardFunc(void (*func)(unsigned char key, int x, int y)); -  sets the keyboard callback for the current window
void glutMouseFunc(void (*func)(int button, int state, int x, int y)); - sets the mouse callback for the current window
void glutMotionFunc(void (*func)(int x, int y)); - sets the motion callback for the current window
void glutPassiveMotionFunc(void (*func)(int x, int y)); - set the passive motion callback for the current window

8. Lights in OpenGL Point light Sun light Spot light Sun: Point: Spot:
glEnable( GL_LIGHTING );
glEnable( GL_LIGHT0 );
GLfloat light0Position[] = {4.0, 4.0, 0.0, 0.0 };
glLightfv(GL_LIGHT0, GL_POSITION, light0Position );
Point:
glEnable( GL_LIGHTING );
glEnable( GL_LIGHT0 );
GLfloat light0Position[] = {4.0, 4.0, 0.0, 1.0 };
glLightfv(GL_LIGHT0, GL_POSITION, light0Position );
Spot:
glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 45.0 );
glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, 4.0 );
GLfloat direction[] = {-1.0, -2.0, 2.0};
glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, direction );

9. Materials in OpenGL
Ambient – factor of reflection (depends on the ambient environment) GL_AMBIENT
Diffuse – factor of diffuse reflection GL_DIFFUSE
Specular – factor of specular reflection GL_SPECULAR
Shininess – factor of concentration of reflected light in a small area around the ideal reflector GL_SHININESS
Emission – factor of emissive color of the material GL_EMISSION
These factors are applied over the faces in three modes: GL_FRONT, GL_BACK and GL_FRONT_AND_BACK

10. Materials in OpenGL Example:
GLfloat ambient[] = { 0.7f, 0.7f, 0.7f, 1.0f };
GLfloat diffuse[] = { 1.0f, 0.0f, 0.0f, 1.0f };
GLfloat specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
GLfloat shininess[] = { 50.0f };
glMaterialfv(GL_FRONT, GL_AMBIENT, ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, specular);
glMaterialfv(GL_FRONT, GL_SHININESS, shininess);

11. Defining a Camera

12. Defining a Camera
void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ, GLdouble centerX, GLdouble centerY, GLdouble centerZ, GLdouble upX, GLdouble upY, GLdouble upZ); - creates a viewing matrix derived from an eye point, a reference point indicating the center of the scene, and an UP vector
eyeX, eyeY, eyeZ specifies the position of the eye point.
centerX, centerY, centerZ specifies the position of the reference point.
upX, upY, upZ specifies the direction of the up vector.

13. Defining a Camera
void gluPerspective(GLdouble  fovy, GLdouble  aspect, GLdouble  zNear, GLdouble  zFar); - specifies a viewing frustum into the world coordinate system
fovy specifies the field of view angle, in degrees, in the y direction.
aspect specifies the aspect ratio that determines the field of view in the x direction. The aspect ratio is the ratio of x (width) to y (height).
zNear specifies the distance from the viewer to the near clipping plane (always positive).
zFar specifies the distance from the viewer to the far clipping plane (always positive).

14. Defining a Camera Example: glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluPerspective( 70.0, 640.0/480.0, 0.1, );
gluLookAt( eyex, eyey, eyez, //eye
0.0, 0.0, 0.0, //center
0.0, 1.0, 0.0 );//up vector