[visionegg] Re: Dropping into C

Thanks Andrew,

This was exactly the info I needed. I was able to compile the vertex
array method and on monday I hope to benchmark it. Best,

Doug


Andrew Straw wrote:

Hi Doug,

You'll want to use Python's distutils to build C extensions[1] to Python. You can (and should) use distutils to compile extensions[2]. The VE has examples of all this, and _draw_in_c.c gets compiled to the .so via the setup.py script. Basically, a "python setup.py build_ext" will build these C extensions. (This happens as a part of the "python setup.py install" process.)

_draw_in_c.c is written in pure C, but if you find that tedious and error-prone, I highly recommend Pyrex[3]. Pyrex is a very-Python-like language for writing extension modules. Think Python-to-C compiler and you'll be in the right ballpark. There are now some examples of Pyrex use in the Vision Egg, and I plan on converting all the SWIG stuff to Pyrex eventually -- when the occasion arises to mess with the SWIG source code. At that point, I'll re-code it in Pyrex rather than deal with SWIG anymore.

[1] http://www.python.org/doc/2.4.2/ext/ext.html
[2] http://www.python.org/doc/2.4.2/dist/describing-extensions.html
[3] http://www.cosc.canterbury.ac.nz/~greg/python/Pyrex/

Douglas Taylor wrote:

Hi Andrew,

I was trying to optimize the dot drawing routine
using the Vertex Array method

xy[:,0] = xstart #where xy is an [npoints][2] array
xy[:,1] = ystart
# Pass a pointer to the start of the point-coordinate array:
glVertexPointerd(xy);
# glVertexPointer(2, GL_DOUBLE, 0, xy); Python did not like it this way
# Enable fast rendering of arrays:
glEnableClientState(GL_VERTEX_ARRAY);
# Render all n points, starting at point 0, render them as POINTS:
glDrawArrays(GL_POINTS, 0, len(xstart));
# Disable fast rendering of arrays:
glDisableClientState(GL_VERTEX_ARRAY);

and on the Mac(10.3 and 10.4) I actually got worse performance than the
GL_POINTS loop method. So I would like to drop into C and I found
the _draw_in_c.c code which looks like a good place to start. I don't
understand however how you generated the .so file. I couldn't find
any examples on the Apple site either. I have XCODE and CodeWarrior.
Could you point me in the right direction here. Thanks much,

Doug


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