# Geometry Maths?

Does anyone have a link about the vector math used in jME?

To be more specific: about (modifing) rotation of objects.

I understand the simple things like rotating an object around the x/y/z axes and so on.

And I can imagine what direction/left/up vectors mean.

I had vectors, matrices, and stuff like that in school as well as in my computer science studies. (called "Analytic Geometry" back then)

But i must confess i simply don't figure out how rotation matrices work in jME or what the .w coordinate of a Quaternion stands for

And i don't have the slightest clue for what 4-dimensional matrices are needed in a 3-dimensional room

One of the best math books that will cover all of that (one that was used for much of the jME code) is:

Mathematics for 3D Game Programming and Computer Graphics

http://www.amazon.com/exec/obidos/tg/detail/-/1584502770/102-0005820-6308104

I want to make an object (i.e. a quad) always face the camera in a 90

Thanks mojo, just ordered that book. :)  Gonna read it over the weekend.

darkfrog

Hm thx for the answer, but i'm too spoiled by google to buy a book for things i can surely find somewhere in the web

Besides, i don't need the whole thing from a to z, but only a few lines of explanation.

And for the billboardNode… i'll try it out, but this won't really solve my problem, as the 90

Well, I'm a professional developer, but have recently decided to make a major commitment in my spare time to learning game development and eventually make it more than a hobby, so I've got a bigger interest than most. :)  The more I can learn about 3d the better off I'll be.

darkfrog

Here’s a couple of good articles:

http://www.gamedev.net/reference/list.asp?categoryid=28

You may also want to check out this one:

http://chortle.ccsu.edu/VectorLessons/vectorIndex.html

Sometimes mathworld can be of help as well:

http://www.mathworld.com/

And I’ve had this book on my shelf for a while now:

Mathematics for Game Developers

I havn’t had the time to look into it that much, but it seems alright.

One of these days I'll know enough to be useful.

darkfrog

Big thx! from me, too, Per.

This is exactely what I had in mind. Especially the gamedev.net link.

Happy to help