How to compile OpenGL programs

[Ichimaru_Gin]

Visual Studio has spoiled me . I need some assistance on how to compile programs using the OpenGL API. I already know that I have hardware accelarated support for OpenGL. Does anyone know the command line functions to use so that I can compile programs? I will start off using the glut libraries until I learn how to create windows using the XWindows system.

Thanks

Specs

Laptop
Fedora Core 8
Nvidia 6400 128 MB ram

Desktop
Fedora Core 9
Nvidia 8800 GT 512 MB

[Negative_3]

I too would like to know.

[dr death]

Example (save as test.c)

#include <GL/freeglut.h>
#include <math.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

#define LIST_EXAMPLE 1

void reshape(int w, int h);
void processNormalKeys(unsigned char key, int x, int y);
void display(void);

int WIDTH = 800;
int HEIGHT = 500;
int window;

int main(int argc, char *argv[])
{
  char *text="Hello World";

  /* Initialise glut */
  glutInit(&argc, argv);
  /* Open the window in the top-left of the screen */
  glutInitWindowPosition(0, 0);
  /* The size of the window */
  glutInitWindowSize(WIDTH, HEIGHT);
  /* Set the display mode */
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  window = glutCreateWindow("My Window");

  /* The function to call when the windowing system says the screen
   * needs to be redrawn */
  glutDisplayFunc(display);

  /* The function to call when the window is resized */
  glutReshapeFunc(reshape);

  /* Process keyboard events */
  glutKeyboardFunc(processNormalKeys); 
  glutSpecialFunc(NULL); 

  /* Process mouse events */
  glutMouseFunc(NULL);

  /* Non-passive (only when a button is down) routine */
  glutPassiveMotionFunc(NULL);
  glutMotionFunc(NULL);

  /* Idle function */
  glutIdleFunc(display);

  /* Create something to draw on the screen */
  glNewList(LIST_EXAMPLE, GL_COMPILE);
  glPushMatrix();
  /* Set up normalised 2D coordinates*/
  glLoadIdentity();
  gluOrtho2D(0.0, 1.0, 0.0, 1.0);
  /* Text at the center of the screen */
  glRasterPos3d(0.5 - glutBitmapLength(GLUT_BITMAP_HELVETICA_12, (unsigned char*)text)/(2.0*WIDTH),
		0.5 -  glutBitmapHeight(GLUT_BITMAP_HELVETICA_12)/ (2.0*HEIGHT),
		0.0);
  glutBitmapString(GLUT_BITMAP_HELVETICA_12, (unsigned char*)text);
  glPopMatrix();
  glEndList();

  glutMainLoop();

  return 0;
}

void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  /* Run the list */
  glCallList(LIST_EXAMPLE);

  glutSwapBuffers();
}

void reshape(int w, int h)
{
  /* Set the viewport to the new width and height */
  glViewport(0, 0, w, h);
  /* update variables */
  WIDTH = w;
  HEIGHT = h;
}

void processNormalKeys(unsigned char key,
		       __attribute__((unused)) int x,
		       __attribute__((unused)) int y)
{
  char *text="Goodbye World";

  switch (key)
    {
    case 0x1B: /* Esc */
      glutDestroyWindow(window);
      break;
    case 'a' :
    case 'A' :
      glDeleteLists(LIST_EXAMPLE, 1);
      glNewList(LIST_EXAMPLE, GL_COMPILE);
      glPushMatrix();
      /* Set up normalised 2D coordinates*/
      glLoadIdentity();
      gluOrtho2D(0.0, 1.0, 0.0, 1.0);
      /* Text at the center of the screen */
      glRasterPos3d(0.5 - glutBitmapLength(GLUT_BITMAP_HELVETICA_12, (unsigned char*)text)/(2.0*WIDTH),
		    0.5 -  glutBitmapHeight(GLUT_BITMAP_HELVETICA_12)/ (2.0*HEIGHT),
		    0.0);
      glutBitmapString(GLUT_BITMAP_HELVETICA_12, (unsigned char*)text);
      glPopMatrix();
      glEndList();
      break;
    }
}

Compile with

gcc -ansi -Wall -O3 -o test test.c -lglut

And run

./test

[Ichimaru_Gin]

Thanks, but I will be using the g++ compiler - I'd be using the same parameters correct?

[dr death]

Should be the same. I see that the freeglut headers have a

#ifdef __cplusplus
    extern "C" {
#endif

so they should handle name mangling just fine.

Libraries are in /usr/lib, include files in /usr/include, so there should be no problems there. Just make sure that you have the freeglut-devel and mesa-libGL-devel packages installed. If you want to link against 3rd party libraries, then specify their location with the -L parameter (e.g. -L /usr/lib/nvidia/ -lGL)

[dejai]

I wrote my first open gl application with emacs :P I love that program.

[Ichimaru_Gin]

Thanks, I'm going to give that a try. I'll let you know how it works out.

[nilabhnikunj]

hi, can any one help me which headers to use for compiling open gl codes ... am new to open gl and trying to learn.
I wrote a simple code


#include "/usr/include/GL/gl.h"
void display()
{
int p[2][2]={{0,0},{0,1}};
glBegin(GL_POINTS);
glVertex2iv(p);
glEnd();
glFlush();
}

void myinit()
{
glClearColor(1.0,1.0,1.0,1.0);
glColor3f(1.0,10.0,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho2D(0.0,50.0,0.0,50.0);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc,char **argv)
{
glutInit(&argc,argv);
gutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(500,500);
glutInitWindowPosition(0,0);
glutCreateWindow("Something New");
glutDisplayFunc(display);
myinit();
glutMainLoop();
return 0;
}

on compilation it gave following errors

gcc point.c
point.c: In function ‘display’:
point.c:8: warning: passing argument 1 of ‘glVertex2iv’ from incompatible pointer type
point.c: In function ‘main’:
point.c:25: error: ‘GLUT_SINGLE’ undeclared (first use in this function)
point.c:25: error: (Each undeclared identifier is reported only once
point.c:25: error: for each function it appears in.)
point.c:25: error: ‘GLUT_RGB’ undeclared (first use in this function)

[Reisswolf]

Quick question: Is O3 stable yet? In the past I found that programmes compiled with such aggressive optimisation sometimes behaved weirdly.

As a general policy I stick to O2.

[dr death]

You need to install and link to GLUT. OpenGL is just the gl... statments. It doesn't include any windowing stuff.
To install:

yum install freeglut-devel

Use the following include in your source

#include <GL/freeglut.h>

and use "-lglut" when linking.

[nilabhnikunj]

Thanks for replying sir , but after installing the windowing stuff it gave another set of errors and warnings

gcc -ansi -Wall -O3 -o point point.c -lglut
point.c: In function ‘display’:
point.c:8: warning: passing argument 1 of ‘glVertex2iv’ from incompatible pointer type
point.c: In function ‘myinit’:
point.c:19: warning: implicit declaration of function ‘glOrtho2D’
point.c: In function ‘main’:
point.c:25: warning: implicit declaration of function ‘gutInitDisplayMode’
/tmp/cc6HrGFb.o: In function `myinit':
point.c:(.text+0x63): undefined reference to `glOrtho2D'
/tmp/cc6HrGFb.o: In function `main':
point.c:(.text+0xfe): undefined reference to `gutInitDisplayMode'
point.c:(.text+0x199): undefined reference to `glOrtho2D'
collect2: ld returned 1 exit status
[regular@localhost ~]$ 

kindly guide once again
thank you ...........

[pankajp]

I'm not actually an opengl programmer but based on a few sample files which i have i could modify your sample to make it run. There was a few typo in your file and also the usage of glVertex2iv was different and also glOrtho2D did not exist in the gl libraries so i replaced it with an equivalent form of glOrtho. Also i added the reshape function to display properly and glClear(GL_COLOR_BUFFER_BIT);
The modified code is as follows

#include "GL/glut.h"
void reshape(int w, int h)
{
  glViewport(0, 0, w, h);       /* Establish viewing area to cover entire window. */
  glMatrixMode(GL_PROJECTION);  /* Start modifying the projection matrix. */
  glLoadIdentity();             /* Reset project matrix. */
  glOrtho(0, w, 0, h, -1, 1);   /* Map abstract coords directly to window coords. */
  glScalef(1, -1, 1);           /* Invert Y axis so increasing Y goes down. */
  glTranslatef(0, -h, 0);       /* Shift origin up to upper-left corner. */
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    int p[2][2]={{10,100},{10,11}};
    glBegin(GL_POINTS);
    glColor3f(0.0, 0.0, 1.0);  /* green */
    glVertex2iv(p[0]);
    glVertex2iv(p[1]);
    glEnd();
    glFlush();
}

void myinit()
{
    glClearColor(1.0,1.0,1.0,1.0);
    glColor3f(0.0,1.0,0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    //glOrtho2D(0.0,50.0,0.0,50.0);
    glOrtho(0.0,50.0,0.0,50.0, 0.0,0.0);
    glMatrixMode(GL_MODELVIEW);
}

int main(int argc,char **argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutInitWindowSize(500,500);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Something New");
    glutDisplayFunc(display);
    myinit();
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}

Also if you want to know the sample from where i got the idea it is

#include <GL/glut.h>

void reshape(int w, int h)
{
  /* This short bit of code sets up the coordinate
     system to correspond to actual window coodrinates.  This code
     wouldn't be required if you chose a (more typical in 3D) abstract
     coordinate system. */

  glViewport(0, 0, w, h);       /* Establish viewing area to cover entire window. */
  glMatrixMode(GL_PROJECTION);  /* Start modifying the projection matrix. */
  glLoadIdentity();             /* Reset project matrix. */
  glOrtho(0, w, 0, h, -1, 1);   /* Map abstract coords directly to window coords. */
  glScalef(1, -1, 1);           /* Invert Y axis so increasing Y goes down. */
  glTranslatef(0, -h, 0);       /* Shift origin up to upper-left corner. */
}

void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_TRIANGLES);
    glColor3f(0.0, 0.0, 1.0);  /* blue */
    glVertex2i(0, 0);
    glColor3f(0.0, 1.0, 0.0);  /* green */
    glVertex2i(200, 200);
    glColor3f(1.0, 0.0, 0.0);  /* red */
    glVertex2i(20, 200);
  glEnd();
  glFlush();  /* Single buffered, so needs a flush. */
}

int main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutCreateWindow("single triangle");
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}

Hope you can find the relevant things by a bit searching around (man pages help too)

[dr death]

You have some typos there.

1) You want gluOrtho2D, not glOrtho2D
2) glutInitDisplayMode, not gutInitDisplayMode

Note that glOrtho multiples the current matrix whereas gluOrtho2D sets up a new projection matrix

[nilabhnikunj]

am sorry to disturb you two again but thing is i don know what do tried to mean by typos ???
and modified code also gave almost similar errors ??

gcc -ansi -Wall -O3 -o po po.c -lglut
po.c: In function ‘myinit’:
po.c:29: warning: implicit declaration of function ‘glOrtho2D’
po.c: In function ‘main’:
po.c:44: error: ‘reshspe’ undeclared (first use in this function)
po.c:44: error: (Each undeclared identifier is reported only once
po.c:44: error: for each function it appears in.)

and sample code given by pankajp was giving some more errors

 vim an.c
[regular@localhost ~]$ gcc -ansi -Wall -O3 -o an an.c -lglut
an.c:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘<’ token
an.c: In function ‘display’:
an.c:20: warning: implicit declaration of function ‘glClear’
an.c:20: error: ‘GL_COLOR_BUFFER_BIT’ undeclared (first use in this function)
an.c:20: error: (Each undeclared identifier is reported only once
an.c:20: error: for each function it appears in.)
an.c:21: warning: implicit declaration of function ‘glBegin’
an.c:21: error: ‘GL_TRIANGLES’ undeclared (first use in this function)
an.c:22: warning: implicit declaration of function ‘glColor3f’
an.c:23: warning: implicit declaration of function ‘glVertex2i’
an.c:28: warning: implicit declaration of function ‘glEnd’
an.c:29: warning: implicit declaration of function ‘glFlush’
an.c: In function ‘main’:
an.c:34: warning: implicit declaration of function ‘glutInit’
an.c:35: warning: implicit declaration of function ‘glutCreateWindow’
an.c:36: warning: implicit declaration of function ‘glutDisplayFunc’
an.c:37: warning: implicit declaration of function ‘glutReshapeFunc’
an.c:37: error: ‘reshape’ undeclared (first use in this function)
an.c:38: warning: implicit declaration of function ‘glutMainLoop’

kindly help me out

[dr death]

Typos means that you typed the commands in wrong by mistake.

On line 29 you need to change to

gluOrtho2D
  ^

On line 44 you need to change to

reshape
    ^