Monthly Archives: May 2007

My Summer of Code begins with PySoy r44

Summer of Code has started just today (even if currently it is only a “Spring of Code” 😀 ) but a little contribution of mine has already made his way inside the SVN repository of PySoy.

But let’s start from the beginning…
After having shown to Arc an early draft of an UML class diagram for the current code I decided to come back to work on some test code I had written in the afternoon.
It was just a classical spinning cube demo to actually compare PyOpenGL versus Pyrex speed, I don’t report the results here because they are quite identical, if I haven’t done any mistake it should be the absolute minimum complexity of the code which actually determined this result.
Anyway, even without this proof I firmly believe in the power and speed of Pyrex. 😉

Going back to my commit, my changes affected a small yet important area of the code, I think we will remember it in the future. 🙂

In src/windows-glx/


In include/gl.pxd:

# Constants
  ctypedef enum:
    # glPush/PopAttrib bits

In src/windows-glx/


Was it better before or now? 😉

Python 2.5 support in globs r46

Yes, I should have written about it when I actually committed the revision, but I forgot completely. 😀
About two months after Python 2.5 has been moved to the current repository of Arch I begun to think that maybe it was time to support the new release of our beloved language/interpreter.

Python transparent logo

I don’t know if it can be called “support”, but at least GL O.B.S. is now aware of it. 🙂
The changes are very simple yet of some importance.
First of all, pysqlite is not needed anymore if you have the integrated sqlite3 module:

if sys.version_info[:2] >= (2, 5):
  from sqlite3 import dbapi2 as sqlite
  from pysqlite2 import dbapi2 as sqlite

Moreover I make use of the updated API of the webbrowser module:

if sys.version_info[:2] >= (2, 5):

Another addition, not related with the support of Python 2.5, is the check_ver function, which checks if a particular version of OpenGL is available on the machine running GL O.B.S., this have opened the possibility to add an OpenGL 2 only test like GLSL_Parallax into benchmarks r47.

Python and GL O.B.S. are getting better and better. 😉

Parallax mapping for the masses

I have spent the last ten days studying hard, reading the first half of the Orange Book (it’s the last book in the list, of course 😀 ), a plethora of papers, many demos code, tons of tutorials and guides, but at last I achieved what I would have never imagined just two weeks ago. 😉

Fixed Pipeline

Per-pixel Lighting

Normal Mapping Parallax Mapping

The GLSL_parallax demo shows per pixel Blinn-Phong shading, specular mapping and tangent space parallax mapping with offset limiting! 😀

Actually I’m not really sure about the correctness of my implementation (especially regarding tangent space lighting) but screenshots demonstrate that I’m close to it.
In the first one the usual and boring OpenGL fixed functionality per-vertex lighting (ambient, diffuse and specular components of a point light with attenuation), in the second one shaders are enabled, but only to calculate lighting on a per-pixel basis. At last, the third and the fourth image show normal and parallax mapping.

Talking in more detail, the code is written for OpenGL 2 only, it makes use of Vertex Buffer Objects and GLSL shaders using core functions.

Here is the magic:

if (withParallax == true) { // alpha channel encodes the height map
  height = scale * texture2D(Tex1, gl_TexCoord[1].st).a - bias;
  TexCoord = gl_TexCoord[0].st + height * ecPos.xy;
if (withNormal == true)
  nor = 2.0 * normalMap.rgb - 1.0; // decoding normal map

Some statistics:

  • 6 varying variables
  • 7 uniform variables (texture samples and enable/disable booleans)
  • 3 texture fetches every fragment processed
  • (24×3)x3 + 24×2 = 432 floats (1728 bytes) stored in VBOs

Enjoy the shaders! 🙂