# 4 by 4 Matrix in maya

There is an entry about matrix resources. Here I want to delve a bit deeper about matrix, especially how we can construct/compose a matrix

I know in maya we have something called bounding box, which is acting like a container for geometry. The bounding box behaves like parallelogram. I tried to created an openGL locator node without defining the proper bounding box. Everytime I hit "F" key to focus the view, It messed up the camera.

http://sk.uploads.im/t/JVBvn.jpg "Matrix"

a11, a12, a13 to represent the x coordinate

a21, a22, a23 to represent the y coordinate

a31, a32, a33 to represent the z coordinate

a41, a42, a43 to represent offset / translation for each individual axis.

Some on internet said the fourth column represents the perspective foreshortening (Don`t know what that means.)

let`s say, I have a locator node that is the child transform1, and transform1 is the child of transform2. When I alter the position of transform1 and transform2. How do I calculate the locator position?

I really have to learn more about linear algebra.

Thanks

I am by no means an expert, but here is how I think about transformation matrices.

So, if you have the following hierarchy:

All you have to do in order to calculate the

`locator1`

's position is to multiply the local matrices going upwards through the hierarchy. So in this case it would be:`locator1_matrix * transform1_matrix * transform2_matrix`

, where the matrices are in local space (the)`matrix`

attribute of a`transform`

nodeThat will give you the locator transformation in the space of whatever the parent of

`transform2`

is, which in this case is world, hence this will be enough. That being said, in Maya you can use the`worldMatrix`

attribute of any transform which is exactly the same as the multiplication above.So to get your locator's world transform using the

`worldMatrix`

attr, you would do this:`locator1_matrix * transform1_worldMatrix`

which is equivalent to the`locator1.worldMatrix`

attribute.As other people have mentioned in the other post, there are a few videos at Cult of Rig that go over math concepts. Here are a couple

http://www.cultofrig.com/2017/06/17/pilot-season-day-8-trigonometry/ http://www.cultofrig.com/2017/06/04/pilot-season-day-5/

As for the

perspective foreshorteningI can't be of much help as I've always used higher level tools to construct my projection matrices in OpenGL (they were similar to this one), so I am not quite sure how that fits in the last column, especially since I haven't done any OpenGL drawing in Maya.