Category Archives: OpenGL

OpenGL

How to get? the GLSL and OpenGL version.

You can get a version from the OpenGL and GL Shading program by:

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glGetString(GL_SHADING_LANGUAG­E_VERSION)

If don’t initialize the OpenGL you can get it:

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OpenGL (null), GLSL (null)

Let’s try one simple example.

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#include <GL/glut.h>
#include
// define the size of the window
#define window_width  640
#define window_height 480
// Main loop function
void main_loop_function()
{
// Clear color screen
// And depth , is used internally to block obstructed objects
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// If don't use the next source code OpenGL will show dizzy content of windows
glutSwapBuffers();
}
// Initialze OpenGL perspective matrix
void GL_Setup(int width, int height)
{
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glEnable( GL_DEPTH_TEST );
gluPerspective( 45, (float)width/height, .1, 100 );
glMatrixMode( GL_MODELVIEW );
}
// Initialize GLUT and start main loop function
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitWindowSize(window_width, window_height);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
glutCreateWindow("www.free-tutorials.org - get? the GLSL version example.");
glutIdleFunc(main_loop_function);
GL_Setup(window_width, window_height);
//next source code will show on shell the OpenGL and GLSL version
printf("OpenGL %s, GLSL %s\n", glGetString(GL_VERSION),glGetString(GL_SHADING_LANGUAGE_VERSION));
glutMainLoop();
}

The output will be print on the shell.

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OpenGL 2.1 Mesa 7.3-devel, GLSL 1.10

How to create an executable in Linux using OpenGL.

I will try to show you briefly how to create Linux OpenGL applications. We check if the graphics card and settings are done correctly, using the command:

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$ glxinfo
name of display: :0.0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: NVIDIA Corporation
server glx version string: 1.4
server glx extensions:
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_SGIX_fbconfig,
    GLX_SGIX_pbuffer, GLX_SGI_video_sync, GLX_SGI_swap_control,
    GLX_EXT_texture_from_pixmap, GLX_ARB_multisample, GLX_NV_float_buffer
...

As freeglut devel package provides libraries for OpenGL. Let’s install that package.

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# yum -y install freeglut-devel

Then we see if we have the necessary files.

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$ cd /usr/include/GL
... GL]$ ls
freeglut_ext.h  gl.h          glut.h       GLwMDrawAP.h  glx_mangle.h  internal
freeglut.h      gl_mangle.h   GLwDrawA.h   glxext.h      glxmd.h
freeglut_std.h  glu.h         GLwDrawAP.h  glx.h         glxproto.h
glext.h         glu_mangle.h  GLwMDrawA.h  glxint.h      glxtokens.h
 

Let’s try a simple… Read More »

Writing a basic game with C++ and OpenGL libs – part 001.

This is a first part tutorial about Linux game using C++ and OpenGL libs. Writing a C++ game can be difficult. You will need to focus on program structure and then to know how to create the necessary classes. Let’s see the files I used:

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display.cpp
display.hpp
game.cpp
game.hpp
main.cpp

The main.cpp file is the main program. This file… Read More »