Are there any good arithmetic for calculating texture coordinates of complex model?
I guess you’re looking for some UV-mapper tool, like this one:
http://www.unwrap3d.com/news.aspx
The math behind this is complex and requires various algorithms to be implemented.
Many 3D programs have such tools included, so when you export a model you have texture coordinates ready.
Can I use such tools in my program for calculating the texture coordinates instead of calculating them by myself?