Tamapolis: Javi Agenjo's personal blog

Real-time graphics is a field ruled by C++, not by imposition, just because the idiosyncracy of the task. We need to do a lot of things and we need them to be done as fast as possible, otherwise we have a drop of the framerate and we loose the feeling that the world is moving.

So C++ works perfect in that field, in the field of real-time standalone graphics applications. But sometimes we want more, we want other things, like flexibility, like on-the-fly coding, like portability, and then we start looking C++ like and old man looks at his wife, yeah, she was adorable, but a thousand years ago.

I like coding graphics, it reminds me drawing and I like drawing. Somehow it is the same in my mind, but with the difference that coding I can make iterative things a lot faster and easier. I am part of a small set of people in the world who know how to draw and how to code graphics, and I want to take advantage of that. I want to explore both fields till the point where they merge in a new form of expression.

So today I’m gonna park my C++ compiler and start with something new, I need a language powerful (but not too much), where I can use my knowledge of graphics but with the flexibility of a playground, a sandbox, where I can add and remove in a simple way, within a keystroke. The idea? To create an application where I can code graphics meanwhile they are renderer, similiar to fluxus but using OpenGL paradigm.

And the awarded platform is… Python!. I know enough of this language to know it fits my needs, there are modules for almost everything and it is made to be confortable to code, but the setting up is going to be a pain in the ass.

So my first task today (and the one I’m going to document) is how to render some stuff in OpenGL using Python,

The setting up

First I have to download a thousand of packages:

• Python compiler (I choose 2.6 because 3.x version still don’t have a good support for most of the libraries)
• PyOpenGL all the binds needed to use OpenGL
• OpenGLContext which is a library wrapping the common stuff in all OpenGL applications, helpful, but this have depencencies too…
• PyDispatcher a library to send messages between elements
• PIL to load images
• Numpy to numerical actions along arrays (important to process meshes… I guess)
• PyGame more or less like OpenGLContext but with more stuff about games
• PyVRML97 this sounds kind of cheesy because who uses VRML now… but OpenGLContext asks for it

To install this libraries is easy, you just need to unzip them and execute from the command line “python setup.py install” inside the folder, and they do the rest.

I needed to test that everything was working so I end up in the website of Bastiaan Zapf: Complete Python OpenGL examples. Lot’s of useful examples of python mixed with OpenGL and with shaders!.

It took me some time to have all the libraries used by him, but it is a nice way to start, to take other person’s work instead of starting from scratch (and giving full credit!).

The first test

But after reading some of the examples propose by Bastiaan I better backup up a little, I mean, I need the basics of the aplication flow inside Python, things like creating a window, reading the keyboard input, rendering the frame, so I will follow the pygame tutorials to see what they suggest… No, too basic. They can be useful but I don’t want to waste time reading them. I just grabbed information to create and destroy the window and to check the keyboard input, for now I don’t need anything else.

I have an idea to start, I’m going to pack most of the import stuff I need to code graphics in some classes, stuff like Shaders and RenderToTexture, that is something common when you start coding in OpenGL, the API is boring and confusing, so the best thing to do is to encapsulate the API in simple calls closer to your mind paradign. I have the code in Bastian examples to compile a shader, so time to take it.

Here is my first “module”, just a small source file that will help me as a guide to future modules, I put there the shader compiler and how to create a box in a call list: GLTools

And then I clean up the Bastiaan file to use my tools and add some small features: Hackpact_dat1

And here are the results:

Cubes and blending

Main changes are to render two cubes instead of one (one in wireframe and one normal) and to use additive blending. I like when you overdraw the scene, it looks “hackerish”.

Conclusion

Hey, programming in python with OpenGL looks easier than what I thought. I don’t have to say the types and the API is totally exposed so I can do most of the regular stuff without thinking too much. The performance is good enough and it blends perfectly with Python.

Tomorrow, more test 🙂

Wednesday, September 2nd, 2009 @ 7:49 pm development
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