Simple OpenGL (SGL)

A simplified, threaded C++ wrapper for OpenGL and GLUT

Features/Objectives:

• Simplify the OpenGL and GLUT interface to make it intuitive like MATLAB.
• Automatic threading for OpenGL windows and processes.
• Allow easy creation of objects and maintenance of object hierarchy.
• Object properties computed/modified according to object hierarchy.
• Easy access & modification to object properties and transformations.
• Allow easy creation and management of multiple windows.

Illustrative Example:

#include <iostream>
#include "sgl/sgl"

#define rand_d (2.0 * ((double)rand()) / ((double)RAND_MAX) - 1.0)  // random number between -1 and 1

int main(int argc, char *argv[])
{
    
    sglFigure myFig; // create sglFigure instance
    myFig.init (); // Display the figure
    
    // draw a sphere
    myFig.addChild ( sglSphere (0.0,0.0,2.0, 1.0, 1.0,0.2,0.0) );
    //                    ^^     cx, cy, cz, rad,   r,  g,  b
    
    // draw multiple random boxes and rotate them about random axes
    for (int i=0; i<10; ++i) {
        sglBox* bx = myFig.addChild ( sglBox (rand_d, rand_d, rand_d,  // x1,y1,z1
                                              rand_d, rand_d, rand_d,  // x2,y2,z2
                                              0.4,0.4,0.8, 0.6) );     // r,g,b, alpha
        bx->addTransformation ( sglRotate (30, rand_d, rand_d, rand_d) );
        //                         ^^   angle,      x,      y,      z   (angle and axis of rotation)
    }
    
    myFig.get_key("press any key to save file.\n");  // Pause for keyboard input
    myFig.save_as_image("crystal_red_dwarf.png");  // save as image (required OpenCV)
    myFig.get_key("press any key to exit.\n");
}

Output screenshot ("crystal_red_dwarf.png"):

---

Developers / contributors:

• Subhrajit Bhattacarya (maintainer): [email protected]

Accompanying modules (code included -- see individual code file/folder):

• GLT-ZPR: Zoom-pan-rotate mouse manipulation module for GLUT. Version 0.4, October 2003 by Nigel Stewart. License: GNU Lesser General Public License. Link: http://www.nigels.com/glt/gltzpr/

Dependencies:

• OpenGL, freeGLUT
• Xorg X server, X11 misc extensions, libXi
• Boost
• OpenCV (optional - for saving screenshots)

TODO:

• Add more objects to the 'sgl_objects' folder. See the '_template.h' file for a template.
• Allow user to change light and display settings.
• Implement textures.

---

Use:

Install headers in the system folder and compile example programs:

• cd to the folder containing this README file

• Install headers (optional) by running:

    sudo make install
  

• Compile the example programs by running:

    make examples
  

Basic usage:

#include "sgl/sgl"
// ...

int main(int argc, char *argv[])
{
    sglFigure my_fig;               // create SGL figure instance
    my_fig.init ();                 // Display the figure
    
    // ...
    
    // Add objects to figure. e.g, sglLine (x0,y0,z0, x1,y1,z1)
    auto my_line = my_fig.addChild ( sglLine (-2.0,0.0,0.0, 2.0,0.0,0.0) );
    // etc...
    
    // Set a property of an object
    my_line->linewidth() = 3.0;
    
    // Access a sub-object of an object (a point for a line)
    my_line->points[0]->color() = sglMake3vec (1.0, 0.0, 0.0);
    
    // Add transformation to an object
    my_line->addTransformation ( sglRotate(30.0,  0.0, 0.0, 1.0) );
    
    // ...
    
    // Pause for keystroke
    my_fig.get_key();
    
    // Animation
    while (true) {
        // change some properties, add/modify objects or sub-objects, etc.
        // ...
        my_fig.flush ();  // flush all pending changes to the figure
        // pause for 100ms, etc.
    }
    
    // ...
}

Available Objects

For the currently available objects, see the sgl/sgl_objects folder. The constructors of each object should be self-explanatory. The template_.icc acts as a guide for creating new objects. More extensive documentation will be created in future.

Suggested compilation options:

Without OpenCV:

g++ -std=gnu++11 -O3 -g -o <program> <program>.cpp -lm -lglut `pkg-config --cflags --libs x11 xi gl glu`

With OpenCV:

g++ -std=gnu++11 -O3 -g -o <program> <program>.cpp -lm -lglut `pkg-config --cflags --libs x11 xi gl glu opencv` -D__opencv=1

(note that the -D__opencv=1 flag is necessary in order to instruct sgl to use the OpenGL library)

---

Compiling and examples:

• This library is (to a large extent) template-based. There is nothing to build. Simply include the file "sgl/sgl" in your code. You can (optionally) install the headers in the system folder by running sudo make install.

• For compiling your program, you'll need to link to the GL, glut and X11 libraries. Besides that, you'll need the Boost library.

• Most of the functionalities are intuitive and easy to find from the code. See the 'examples' folder for examples (run make examples to compile).

---

License:

**************************************************************************
*                                                                        *
*  Simple OpenGL (SGL)                                                   *
*  A simplified, threaded C++ wrapper for OpenGL and GLUT                *
*  Version 1.1b                                                          *
*  ----------------------------------------------------------            *
*  Copyright (C) 2018  Subhrajit Bhattacharya                            *
*                                                                        *
*  This program is free software: you can redistribute it and/or modify  *
*  it under the terms of the GNU General Public License as published by  *
*  the Free Software Foundation, either version 3 of the License, or     *
*  (at your option) any later version.                                   *
*                                                                        *
*  This program is distributed in the hope that it will be useful,       *
*  but WITHOUT ANY WARRANTY; without even the implied warranty of        *
*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
*  GNU General Public License for more details                           *
*  <http://www.gnu.org/licenses/>                                        *
*                                                                        *
*                                                                        *
*  Contact: [email protected], http://subhrajit.net/                   *
*                                                                        *
*                                                                        *
**************************************************************************