What is python-cg?

python-cg is a Python wrapper for NVidia Cg Toolkit runtime. I’ve started it because I like Python, I like NVidia CG and I want to to do some computer game/3d graphicsprototyping and research. Also I still find C++ counterproductive as far as my needs are concerned and I don’t want to waste my time doing boring stuff. Programming in Python is fun.

I know about some projects that were meant to bring CG to Python but as far as I know they’re history now.

Project is hostead at GitHub: https://github.com/jstasiak/python-cg.

What’s the state?

The project is in very early development stage. Overview of what’s supported right now:

• Cg contexts

  • creating

  • destroying

• CgFX effects

  • creating from file

  • creating directly from source code

• accessing effects` techniques and their passes

• accessing effect parameters with their names, semantics and parameter-specific metadata (rows, columns etc.)

• setting sampler parameters and most of numerical parameters

What doesn’t work at the moment and there’s no plan to implement it:

• everything that’s left (well, until I decide I need some of it or someone else does that)

Requirements

This project requires:

• NVidia Cg Toolkit ≥ 3.0

• Python interpreter (+ development files):

  • 2.x ≥ 2.6, or

  • 3.x ≥ 3.2

• C and C++ compiler

Python packages required to build and install python-cg:

• Cython ≥ 0.18

• numpy

To build documentation/run tests you also need:

• Mock ≥ 1.0

• Nose ≥ 1.2

• Sphinx ~ 1.2 (development version)

Documentation

Pregenerated documentation can be found at https://python-cg.readthedocs.org/en/latest/.

You can also build documentation all by yourself by calling:

sphinx-build -b html docs docs/build/html

Generated HTML files are placed in docs/build/html/ directory.

Building

To build the project in place, run:

python setup.py build_ext --inplace

Important information

• This project works with OpenGL and OpenGL only

• It uses row-major matrices by default, just like numpy does

Quickstart

First you need to create an instance of CG class and use it to create new Context:

from cg import CG

cg = CG()
context = cg.create_context()

We want to use an effect to render some stuff so we’re gonna create Effect from file:

effect = context.create_effect_from_file('effect.cgfx')

We now have access to Effect’s techniques and parameters:

for technique in effect.techniques:
   # ...

for parameter in effect.parameters:
   # ...

For the sake of simplicity let’s say we have a parameterless effect with only one Technique:

technique = effect.techniques[0]

Now we can access technique’s passes. Each Pass has methods begin() and end() and the actual drawing has to take place between a call to begin and end:

gl.glClear(gl.GL_COLOR_BUFFER_BIT)

for pass_  in technique.passes:
   pass_.begin()


   gl.glBegin(gl.GL_TRIANGLES)
   gl.glVertex3f(-0.5, -0.5, 0)
   gl.glVertex3f(0.5, -0.5, 0)
   gl.glVertex3f(0, 0.5, 0)
   gl.glEnd()

   pass_.end()

# swap buffers

You can find complete, runnable example application in example directory. Please note that it requires (in addition to python-cg requirements):

• Development version of SFML 2

• Python packages listed in example/requirements.txt:

  pip install -r example/requirements.txt

Then to run the example:

python setup.py build_ext --inplace
PYTHONPATH=. python example/main.py

Testing

To run tests, execute:

python runtests.py

License

© 2013, Jakub Stasiak

This project is licensed under MIT License, see LICENSE file for details.