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.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();

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: 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 );

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 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.

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