Post on 05-Sep-2020
GRAFIKA KOMPUTER~ M. Ali Fauzi
Your First OpenGL Program
Simple Program Architecture
Inisialisasi
Update logika
Rendering
De-Inisialisasi
Keluar ?
RECALL
Recall
OpenGL can’t performing windowing tasks or obtaining user input, but GLUT
THE CODE
#include <windows.h>
#include <GL/glut.h>
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
#include <windows.h>
#include <GL/glut.h>
The Header
// For MS Windows
#include <windows.h>
#include <GL/glut.h>
The Header
// GLUT, includes glu.h and gl.h/* Handler for window-repaint event. Call back when the window first appears and whenever the window needs to be re-painted. */
The Main
/* Main function: GLUT runs as a console application starting at main() */GLUT command startswith glut*
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The Main
// Initialize GLUT
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_DOUBLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The Main
// Specify the display Mode – RGB or color Index, single or double Buffer
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The Main
// Create a window with the given title// Set the window's initial width & height
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The Main
// Position the window's initial top-left corner
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The Main
// Register display callback handler for window re-paint
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The Main
// Enter the infinitely event-processing loop
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Set background color to black and opaque
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Clear the color buffer
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Draw a Red 1x1 Square centered at origin
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Red
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Each set of 4 vertices form a quad
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Render
OPENGL COMMAND SYNTAX
Command Syntax
OpenGL commands use the prefix gl and initial capital letters for each word making up the command name (recall glClearColor(), for example)
Command Syntax
OpenGL defined constants begin with GL_, use all capital letters, and use underscores to separate words (for example,GL_SINGLE).
Command Syntax
You might also have noticed some seemingly extraneous letters appended to some command names (forexample, the 3f in glColor3f()and 2f in glVertex2f()).
Command Syntax
glVertex2f()
Number of Component
2 – (x, y)
3 – (x, y, z)
4 – (x, y, z, w)
Data Typef - floati – integerd – doubleEtc.
Command Syntax
Command Syntax
Thus, the two commands are equivalent
glVertex2i(1, 3);
glVertex2f(1.0, 3.0);
Command Syntax
> When only x and y are
specified, z defaults to 0.0and w defaults to 1.0.
> When x, y, and z are
specified, w defaults to 1.0.
Command Syntax
Thus, the two commands are equivalent
glVertex2i(1, 3);
glVertex3f(1.0, 3.0, 0.0);
Command Syntax
Some OpenGL commands can take a final letter v, which indicates that the command takes a pointer to a vector (or array) of values, rather than a series of individual arguments.
Command Syntax
glColor3f(1.0, 0.0, 0.0);
GLfloat color_array[] = {1.0, 0.0, 0.0};
glColor3fv(color_array);
OPENGL AS A STATE MACHINE
Command Syntax
OpenGL is a state machine, particularly if you’re using the fixed-function pipeline. You put it into various states (or modes) that then remain in effect until you change them.
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Red
void display() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(-0.5f, -0.5f);
glVertex2f( 0.5f, -0.5f);
glColor3f(0.0f, 1.0f, 0.0f);
glVertex2f( 0.5f, 0.5f);
glVertex2f(-0.5f, 0.5f);
glEnd();
glFlush();
}
The Display
// Green
GLUT CALLBACK FUNCTIONS
Callback Func
> Your OpenGL program will be in infinite loop> Event-driven: Programs that use windows
~ Input/Output~ Wait until an event happens and then execute some pre-defined functions according to the user’s input
Callback Func
> Your OpenGL program will be in infinite loop> Event-driven: Programs that use windows
~ Input/Output~ Wait until an event happens and then execute some pre-defined functions according to the user’s input
Callback Func
Events – key press, mouse button press and release, window resize, etc.
Callback Func
Callback function : Routine to call when an event happens
~ Window resize or redraw~ User input (mouse, keyboard)~ Animation (render many frames)
Callback Func
“Register” callbacks with GLUT
glutDisplayFunc( my_display_func );
glutIdleFunc( my_idle_func );
glutKeyboardFunc(my_key_events_func);
glutMouseFunc (my_mouse_events_func);
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
Callback Func
// Register display callback handler for window re-paint
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
glutCreateWindow("OpenGL Setup Test");
glutInitWindowSize(320, 320);
glutInitWindowPosition(50, 50);
glutDisplayFunc(display);
glutIdleFunc( my_idle_func );
glutKeyboardFunc(my_key_events_func);
glutMouseFunc (my_mouse_events_func);
glutMainLoop();
return 0;
}
Callback Func
Rendering Callbacks
> Callback function where all our drawing is done> Every GLUT program must have a display callback
glutDisplayFunc( my_display_func );
/* this part is in main.c */
Rendering Callbacks
glutDisplayFunc( my_display_func );
/* this part is in main.c */
void my_display_func (void ){glClear( GL_COLOR_BUFFER_BIT );glBegin( GL_TRIANGLE );glVertex3fv( v[0] );glVertex3fv( v[1] );glVertex3fv( v[2] );
glEnd();glFlush();
}
Idle Callbacks
> Use for animation and continuous update
~ Can use glutTimerFunc or timed callbacks for animations
glutIdleFunc( idle );
Idle Callbacks
glutIdleFunc( idle );
void idle( void ){
/* change something */t += dt;glutPostRedisplay();
}
User Input Callbacks
> Process user input
glutKeyboardFunc(my_key_events);
User Input Callbacks
glutKeyboardFunc(my_key_events);
void my_key_events(char key, int x, int y){switch ( key ) {case ‘q’ : case ‘Q’ :
exit ( EXIT_SUCCESS);break;
case ‘r’ : case ‘R’ :rotate = GL_TRUE;break;
}}
Mouse Callbacks
> Captures mouse press and release events
glutMouseFunc( my_mouse );
Mouse Callbacks
glutMouseFunc( my_mouse );
void myMouse(int button, int state, int x, int y)
{if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
{…}
}
Events in OpenGLEvent Example OpenGL Callback Function
Keypress KeyDown
KeyUp
glutKeyboardFunc
Mouse leftButtonDown
leftButtonUp
glutMouseFunc
Motion With mouse press
Without
glutMotionFunc
glutPassiveMotionFunc
Window Moving
Resizing
glutReshapeFunc
System Idle
Timer
glutIdleFunc
glutTimerFunc
Software What to draw glutDisplayFunc
Event Queue
Event queue
Keyboard
Mouse
Window
….
Mouse_callback() {….{
Keypress_callback() {….{
window_callback() {….{
MainLoop()
Cheers, Old Sport~ M. Ali Fauzimoch.ali.fauzi@gmail.com