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Nov 232012

Both FreeGLUT and GLUT allow us to define an OpenGL context with multisampling. However the number of samples is fixed (4) and I’ve not found a way to change it using the API.

In here we’re going to see how to hack FreeGLUT so that we can change the default number of samples. This can be achieved either by changing the default value, or by adding a new function to set this value.

Note: This hack should be used only for testing purposes, not for redistribution, as FreeGLUT has a large base of users which already have the official version installed.

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Nov 132012

OpenGL renders to framebuffers. By default OpenGL renders to screen, the default framebuffer that commonly contains a color and a depth buffer. This is great for many purposes where a pipeline consists of a single pass, a pass being a sequence of shaders. For instance a simple pass can have only a vertex and a fragment shader.

For more complex graphical effects or techniques, such as shadows or deferred rendering, multiple passes are often required, where the outputs of a pass are inputs of the following pass, for instance as textures. In this context, instead of rendering to screen, and then copying the result to a texture it would be much nicer to render to texture directly. The figure shows a two pass pipeline, where the first produces three textures that are used in the second pass to compose the final image. This is one of the advantages of framebuffer objects: we can render to multiple outputs in a single pass.

Besides, rendering to screen requires the outputs to be of a displayable format, which is not always the case in a multipass pipeline. Sometimes the textures produced by a pass need to have a floating point format which does not translate directly to colors, for instance the speed of a particle in meters per second.

In this short tutorial we will see how a framebuffer object can be created, and used with shaders. A demo is also provided with full source code, and a VS 2010 solution.

Sep 242012

 Patrick Cozzy, Christophe Riccio (eds)

Since I’m one of the authors of a couple of chapters in this book I’ll refrain from commenting on it. Check out the companion site, it is full of information, includes 5 sample chapters and all the companion source code.

More information about this title at or

Jul 102012

I’ve been working for some time with wxWidgets. The only thing I’ve missed, regarding OpenGL, is the ability to define my own OpenGL context, in particular Core profile and Debug contexts.

To be able to set a context we, or the toolkit we’re using, must use the wglCreateContextAttribsARB function, as defined in the WGL_ARB_create_context extension. As it happens, wxWidgets uses wglCreateContext, hence no OpenGL context can be explicitly defined using the provided source code for the current release (2.9.4).

As OpenGL context setting is not yet in the roadmap for future releases of wxWidgets, nor is it in its Todo List, I’m sharing a solution for this issue.

The solution is for the Windows platform, but other platforms should be as easy to change as well.

Note: I make no claim regarding the quality of the solution, it worked for me, and that’s all I claim. If anyone knows of a better way of doing this comments are most welcome, as they may prove useful for other readers (and me as well :-) ).

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May 312012

Bloodshed Dev-C++ is a full-featured Integrated Development Environment (IDE) for the C/C++ programming language. It uses Mingw port of GCC (GNU Compiler Collection) as it’s compiler. Dev-C++ can also be used in combination with Cygwin or any other GCC based compiler.

Here is a short tutorial that was pointed to me to setup Dev C++ with OpenGL. The tutorial  is from the collection of Programming Tutorials and Lecture Notes from the Computer Science Department of Central Connecticut State University.

Feb 212012

The updated version of GLSL tutorial. Only the core version will be dealt in this tutorial.

The tutorial is, and will be in the near future, in construction. I don’t plan to close it, at least in the near future, unless a new version of OpenGL changes everything again.

I’ll be adding content from time to time, initially to get the base complete, and afterwards to provide examples.

The tutorial does not intend to replace the specs as THE source to fully grasp GLSL and OpenGL. The specs are essential, but can be hard to start learning. So consider the tutorial as a gentle introduction to the theme.

As always, your cooperation is a must to get things right. Tutorials always have bugs, mistakes, and things that are not clearly explained. Furthermore, I might get somethings wrong, but please be gentle :) Your feedback is important.

Well, this is it. Have fun playing with GLSL and OpenGL!

Move on to the Index.

Jan 292012

VSMathLib, a part of the Very Simple Libraries framework, has suffered a minor update. The modelview matrix has been split into two matrices: model and view. The modelview matrix is still available, but now it is a computed matrix. The programmer should use the two individual matrices, model and view, and the lib will compute the modelview, actually called VIEW_MODEL, as required.

The PROJMODELVIEW has been renamed to PROJ_VIEW_MODEL since this is the actual order of the matrix multiplication.

Besides that the lib works as usual. Comments are most welcome as usual.

Jan 022012

Very Simple OpenGL Information Lib – OpenGL has a rich set of functions to query its state. It is possible to get information on just about anything, from which shaders are attached to a program, to the values of uniforms, or the properties of the textures currently bound.

However, it is also true, that to get some of this information a lot of code is required. When debugging, we end up writing code to access this and that information over and over again.

This lib attempts to provide all the information with a minimal effort to the developer, for textures, buffers, GLSL programs, shaders, and variables, and a few more items.

Dec 152011

One of the bugs reported in here has been corrected. The uniform buffer data size is now reported correctly.

The other two bugs remain, unfortunately. Querying the primitive counter still gives zero, and glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS_ARB) still crashes the application.