OpenGL programming in C

[Lster]

Hi all

So I already know (a bit!) of OpenGl (on Windows) and wanna be able to do OpenGL in C on Ubuntu. Im sure there was a thread a while back that was about this but I cant find it. I remember needing to install dev libraries... can anyone tell me which to install. Also, a small OpenGL program to test would be great.

Thanks,
Lster

[Wybiral]

You should go to synaptic...

First, and MOST important, you need: build-essential
It's the package that has all of your C standard headers and whatnot.

Then, you'll want an easy way to initialize a window with an OpenGL surface...
I would suggest SDL for that, so runtime and dev libraries: libsdl1.2debian & libsdl1.2-dev

Now you're going to need OpenGL (obviously)...
The development libraries would be: libgl1-mesa-dev & libglu1-mesa-dev

You should have the GL runtimes installed already (I think they come installed).

Anyway, good luck... OpenGL is a lot of fun.

OH! While you're there, you might want to go ahead and grab: libsdl-image1.2 & libsdl-image1.2-dev

SDL_image will make loading textures for SDL and OpenGL a breeze (in all kinds of formats too)

You can knock all of those out from the command line with:


sudo apt-get install build-essential libsdl1.2debian libsdl1.2-dev libgl1-mesa-dev libglu1-mesa-dev libsdl-image1.2 libsdl-image1.2-dev

[Lster]

Thank you Wybiral. Ive installed all the packages! I am not familiar with SDL (but I wanna use it) so could you post a simple C app that sets up the screen and renders a triangle (or something simple!).

Once into OGL Im fine... Thanks,
Lster

[Wybiral]

Something like this...



// Save as:
// triangle.c
//
// Compile with:
// gcc triangle.c -o triangle -lSDL -lGLU -lGL
//
// Execute with:
// ./triangle

#include <GL/gl.h>
#include <GL/glu.h>
#include <SDL/SDL.h>

// Initialize opengl...
void init_opengl(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
gluPerspective(60, (GLfloat)width/height, 1, 2000);

glMatrixMode(GL_MODELVIEW);
glEnable(GL_DEPTH_TEST);
}

// Initialize an SDL_Surface as the window surface
// Most of this should explain itself...
SDL_Surface* init_sdl(int width, int height)
{
SDL_Surface* surface;
if(SDL_Init(SDL_INIT_VIDEO)< 0)
{
return NULL;
}
const SDL_VideoInfo* info = SDL_GetVideoInfo();
if(!info)
{
return NULL;
}
int flags = SDL_OPENGL | SDL_GL_DOUBLEBUFFER;
if (info->hw_available)
{
flags |= SDL_HWSURFACE;
}
else
{
flags |= SDL_SWSURFACE;
}
surface=SDL_SetVideoMode(width, height, info->vfmt->BitsPerPixel, flags);
if(surface==0)
{
return NULL;
}
return surface;
}

int main()
{
// Create our window and initialize opengl...
SDL_Surface* buffer = init_sdl(640, 480);
init_opengl(640, 480);

// OpenGL code...
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0, 0, -5);
glBegin(GL_TRIANGLES);
glColor3ub(0, 255, 0); glVertex2i( 0, 1);
glColor3ub(255, 0, 0); glVertex2i(-1,-1);
glColor3ub(0, 0, 255); glVertex2i( 1,-1);
glEnd();

// Swap buffers...
SDL_GL_SwapBuffers();

// Pause for a couple of seconds...
SDL_Delay(2000);
}


Good luck!

Btw, SDL also has a nice event system for key/mouse/window events.
There are also more SDL libraries that you can use in combination with SDL+OpenGL.
It truly is the easiest way to handle portable OpenGL code.

[Lster]

Thank you again - that was perfect. I will now go learn SDL - it sounds very good indeed :).

Lster

[Lster]

Wow... SDL is easy - Ive already learnt how to get keyboard/ mouse input! I look at a Nehe tutorial for OpenGL (with SDL) it has a way to load a .bmp. I really wanna load PNGs but cant find anything on how to...

Can anyone make me a small PNG load demo... that would rock!

Thanks,
Lster

[xtacocorex]

From quickly looking at stuff, the third paragraph here has a means to load images:
http://www.de-brauwer.be/wiki/wikka.php?wakka=SDLPlayground

[Lster]

Im fine now... That was a bit tricky though. SDL's website is very good :).

[tunisia]

So I have been playing with C for about two months. Are there any good OpenGL tutorials for linux that I might have any chance of understanding?

thanks

[Lux Perpetua]

Try these: http://nehe.gamedev.net/

(By the way, just FYI, since your question does not continue the original topic, this belongs in a new thread.)