Trigonometry and vector/matrix algebra are the principles that 3D graphics are built up off. Without an understanding of them its pretty hard to fully appreciate what is going on. If you're not that comfortable with maths or just have gaps in your knowledge then i recommend a maths book.

I have used this book and it helps alot...

3D maths primer for 3D Graphics/Games.

http://www.amazon.com/Primer-Graphics-Development-Wordware-Library/dp/1556229119