[vtkusers] vtkCamera focal distance

[Bruno Cafaro]

Hi All,
hope someone can help:
I use vtk 5.8 and i'm tryng to get the K matrix for the vtkCamera, as 
defined in Hartley and Zisserman:

         alpha_x    s               p_x
K =                  alpha_y    p_y
                                         1

I know it is based on the OpenGL camera, so i already gave a look to:

http://ksimek.github.io/2013/06/03/calibrated_cameras_in_opengl/

and

http://strawlab.org/2011/11/05/augmented-reality-with-OpenGL/

However i am not interesed in setting a particular value for the alpha_x 
and alpha_y, but only in retrieving their values, as the i need to 
reproject some points which are not in the renderer, in the same camera, 
for postprocessing. What i need is to know the alpha_x and alpha_y 
values, also with p_x and p_y.

For what i have understood in the previous posts i should use 
vtkCamera::GetProjectionTransformMatrix(aspect,ranges[0],ranges[1]) 
where aspect=window_width/window_eight and ranges come from 
vtkCamera::GetClippingRange(ranges)

the result i get is this:
2.79904     0                 0                 0
0                3.73205      0                 0
0                0                 -1000.02     -10.0001
0                0                 -1                 0

but i'm almost sure there is something wrong.

-- 
Bruno Cafaro
PhD Student
Dip.to Ingegneria informatica, automatica e gestionale "Antonio Ruberti"
Università "La Sapienza"
Via Ariosto, 25
00185 Roma
Tel: +390677274155