[vtkusers] perspective transform in vtkCamera

[David Gobbi]

Hi Francesco,

More correctly, the variables that you are interested
in are the 
PerspectiveTransform and the ViewTransform.  The
variable called
"Transform" doesn't become part of the final
projection matrix, it is
just used for a few one-off computations.

The ViewTransform and the PerspectiveTransform are
used directly by OpenGL
in the vtkOpenGLCamera class, the PerspectiveTransform
is loaded as the
OpenGL PROJECTION matrix and the ViewTransform is
concatenated with
the current OpenGL MODELVIEW matrix.

Good descriptions of the PROJECTION and MODELVIEW
matrices can be
found in the OpenGL Programming Guide, which is
available online
in PDF format.

Cheers,
  - David


--- francesco caruso <guernika_devel at yahoo.it> wrote:
> hello vtkusers
> 
> I've noticed that in every instance of vtkCamera
> there are two protected
> variables of type vtkPerspectiveTransform:
> - vtkPerspectiveTransform* PerspectiveTransform
> - vtkPerspectiveTransform* Transform
> 
> I'd like to understand what are the meaning of this
> two variables
> and how they are concatenated to obtain the
> effective projection matrix.
> 
> Thanks in Advance
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