Development of Interactive 3D Virtual

World Applications

Lab exercises by

Assoc. Prof. Dr. Emiliyan Petkov

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

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

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.dllglu.h, libglu32.a, glu32.dllglut.h, libglut32.a, glut32.dll

Creating models 10 graphics primitivesglBegin( GL_POLYGON );

glVertex3f( 0.0, 0.5, 0.0 );glVertex3f( 0.75, -0.5, 0.0 );glVertex3f( -0.75, -0.5, 0.0 );

glEnd();

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

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

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

Lights in OpenGL Point light Sun light Spot light

Sun: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 );

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

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);

Defining a Camera

Defining a Camera void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble ey

eZ, 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.

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).

Defining a Camera

Example: glMatrixMode( GL_PROJECTION ); glLoadIdentity(); gluPerspective( 70.0, 640.0/480.0, 0.1, 100.0 ); gluLookAt( eyex, eyey, eyez, //eye 0.0, 0.0, 0.0, //center 0.0, 1.0, 0.0 );//up vector