Ok, I have an app which draws a square 50px x 50px, However, I don’t understand how it achieves this. App = 500x500px
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glVertex3f(-1.0f, 1.0f, 0.0f);
//So each 1.0f represents a unit 1/10 of the window size. Where was this set?
//And why, is the Z arg in glTranslate = -6??
Any help would really be appreciated, im trying to understand the basics of this app, this isn’t for homework or anything…
Here is the code in case you need a reference:
/*
When creating your project, uncheck OWL,
uncheck Class Library, select Static
instead of Dynamic and change the target
model to Console from GUI.
Also link glut.lib to your project once its done.
*/
#include “Stdafx.h”
#include <windows.h> // Standard Header For Most Programs
#include <gl/gl.h> // The GL Header File
#include <gl/glut.h> // The GL Utility Toolkit (Glut) Header
void init ( GLvoid ) // Create Some Everyday Functions
{
glShadeModel(GL_SMOOTH); // Enable Smooth Shading
glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black Background
glClearDepth(1.0f); // Depth Buffer Setup
glEnable(GL_DEPTH_TEST); // Enables Depth Testing
glDepthFunc(GL_LEQUAL); // The Type Of Depth Testing To Do
glEnable ( GL_COLOR_MATERIAL );
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}
void display ( void ) // Create The Display Function
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glLoadIdentity(); // Reset The Current Modelview Matrix
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();
glutSwapBuffers ( );
// Swap The Buffers To Not Be Left With A Clear Screen
}
void reshape ( int w, int h ) // Create The Reshape Function (the viewport)
{
glViewport ( 0, 0, w, h );
glMatrixMode ( GL_PROJECTION ); // Select The Projection Matrix
glLoadIdentity ( ); // Reset The Projection Matrix
if ( h==0 ) // Calculate The Aspect Ratio Of The Window
gluPerspective ( 80, ( float ) w, 1.0, 5000.0 );
else
gluPerspective ( 80, ( float ) w / ( float ) h, 1.0, 5000.0 );
glMatrixMode ( GL_MODELVIEW ); // Select The Model View Matrix
glLoadIdentity ( ); // Reset The Model View Matrix
}
void keyboard ( unsigned char key, int x, int y ) // Create Keyboard Function
{
switch ( key ) {
case 27: // When Escape Is Pressed…
exit ( 0 ); // Exit The Program
break; // Ready For Next Case
default: // Now Wrap It Up
break;
}
}
void arrow_keys ( int a_keys, int x, int y ) // Create Special Function (required for arrow keys)
{
switch ( a_keys ) {
case GLUT_KEY_UP: // When Up Arrow Is Pressed…
glutFullScreen ( ); // Go Into Full Screen Mode
break;
case GLUT_KEY_DOWN: // When Down Arrow Is Pressed…
glutReshapeWindow ( 500, 500 ); // Go Into A 500 By 500 Window
break;
default:
break;
}
}
void main ( int argc, char** argv ) // Create Main Function For Bringing It All Together
{
glutInit ( &argc, argv ); // Erm Just Write It =)
init ();
glutInitDisplayMode ( GLUT_RGB | GLUT_DOUBLE ); // Display Mode
glutInitWindowSize ( 500, 500 ); // If glutFullScreen wasn’t called this is the window size
glutCreateWindow ( “NeHe’s OpenGL Framework” ); // Window Title (argv[0] for current directory as title)
glutFullScreen ( ); // Put Into Full Screen
glutDisplayFunc ( display ); // Matching Earlier Functions To Their Counterparts
glutReshapeFunc ( reshape );
glutKeyboardFunc ( keyboard );
glutSpecialFunc ( arrow_keys );
glutMainLoop ( ); // Initialize The Main Loop
}
