Question about photomodeling

hello  to all,

I'm a french university student learning multimedia and I've got to write an essay about photomodeling techniques.
I've browse all photomodeler website & the internet but cannot find detailed explanations about the mathematical principle & description of the photomodeling technique &, more particularly, how applications like Photomodeler are programmed from these mathematicals models.

Thanks to this website & the free version of Photomodeler offered, I get the whole informations for the major corpse of my paper but my instructor insist on the fact i must describe clearly (& deeply) how from photographs you can get 3 dimensionnal models...

I hope my request is clear since my english isn't fluent...

Does somebody own a detailed documentation about this subject or know a website adress where i can get these preciouses informations ?

Thanx to all

A good site is www.realviz.com (french company) and then try some of the CAD ones such as www.vexcel.com.