tirengarfio

08-24-2006, 02:04 AM

Hi!

at the top of page 9 of this document about augmented reality:

http://www.vision.ee.ethz.ch/~tquack/hohl_quack_augmentation.pdf

it talks about the projection matrix, considering it, as you see, as a 3x4 matrix.

But i just found out, projection matrix in opengl is a 4x4 matrix!

So, the first term ((x y 1)) of the relation is not correct.

So, What is the correct relation?

Another question:

I have drawn a point 3d at (10, 10, 10) in my opengl space and my projection matrix is this:

0.0075 0.0000 0.0000 0.0000

0.0000 0.0100 0.0000 0.0000

0.0000 0.0000 0.0050 0.0000

0.0000 0.0000 0.0000 1.0000

when i multiplicate it by the coordinate (10, 10, 10) i get this coordinates (0.075, 0.1, 0.05, 1.0)

I thought they would be the coordinates of the projection of that point. so they will be something like (10,10) or (23,23), but im wrong, it think...

What are this last coordinates (0.075, 0,1, 0.05, 1.0) and what is the relation with the projection of the point 3d?

at the top of page 9 of this document about augmented reality:

http://www.vision.ee.ethz.ch/~tquack/hohl_quack_augmentation.pdf

it talks about the projection matrix, considering it, as you see, as a 3x4 matrix.

But i just found out, projection matrix in opengl is a 4x4 matrix!

So, the first term ((x y 1)) of the relation is not correct.

So, What is the correct relation?

Another question:

I have drawn a point 3d at (10, 10, 10) in my opengl space and my projection matrix is this:

0.0075 0.0000 0.0000 0.0000

0.0000 0.0100 0.0000 0.0000

0.0000 0.0000 0.0050 0.0000

0.0000 0.0000 0.0000 1.0000

when i multiplicate it by the coordinate (10, 10, 10) i get this coordinates (0.075, 0.1, 0.05, 1.0)

I thought they would be the coordinates of the projection of that point. so they will be something like (10,10) or (23,23), but im wrong, it think...

What are this last coordinates (0.075, 0,1, 0.05, 1.0) and what is the relation with the projection of the point 3d?