[vtkusers] Need help integrating VTK with an existing OpenGL application (translating glFrustum and gluLookAt calls to VTK)

[Alethea Bair]

That's not quite correct. There is no way to use glPerspective to get
non-regular trapezoids for the frustum shape. glFrustum does allow this.
Unfortunately, I don't know enough about vtkCamera to give advice there.

-Alethea

> You can calculate the values of six arguments of glFrustum from the four
> arguments of gluPerspective, and vice versa.
>
> Weiguang
>
> On Thu, 3 Jan 2008, Mark Waligora wrote:
>
>> Weiguang,
>>
>> Thanks for the reply.  I have no problem using the vtk classes in place
>> of
>> code that I already have.  My issue is that I'm not certain how to use
>> the
>> vtkCamera in place of my glFrustum call when I am creating a frustum
>> where,
>> for example, both the left and right sides of the front face of the
>> frustum
>> volume lie on the negative side of the y axis.  From what I can tell,
>> the
>> vtkCamera can be given a viewing angle and a near and far plane, but
>> that
>> gives me the equivalent control of a gluPerspective call, which is more
>> limited than the functionality that glFrustum provides.  I noticed there
>> was
>> a function to multiply in additional matrices to the camera's
>> transformation
>> matrix, but I don't think that would be quite what I want either.
>>
>> -Mark Waligora
>>
>> On Jan 3, 2008 1:08 PM, Weiguang Guan <guanw at rhpcs.mcmaster.ca> wrote:
>>
>>> Hi Mark,
>>>
>>> If you decide to move on to vtk, then you shouldn't called gl commands
>>> directly. vtkCamera contains methods that implement what you want to
>>> do.
>>>
>>> Weiguang
>>>
>>> On Thu, 3 Jan 2008, Mark Waligora wrote:
>>>
>>>> Hey all,
>>>> I've done quite a bit of searching and reading and am having some
>>> trouble
>>>> getting started integrating VTK into my application.  I'm a new user,
>>> but
>>>> I've spent enough time looking that I don't think I'm missing anything
>>> too
>>>> obvious.
>>>>
>>>> I have a fairly simple visualization application written with OpenGL.
>>>> I
>>>> want to visualize some more complicated data sets, so I wanted to
>>>> write
>>> a
>>>> version that works with VTK.
>>>>
>>>> My visualization application is fed in data from a motion capture
>>> system, so
>>>> right now, every time my application loop updates, it reads the data
>>> from
>>>> the mo-cap system, and updates the rendering with very specific calls
>>>> to
>>>> glFrustum and gluLookAt.  The front face of the frustum volume is
>>>> almost
>>>> never centered around the z axis, so I can't simulate the frustum
>>> creation
>>>> by simply providing a vtkCamera with a position, direction, and
>>>> viewing
>>>> angle.  I need more control of the frustum shape than that
>>>> functionality
>>>> seems to provide.
>>>>
>>>> Can anyone advise me on how to create a simple vtk application with no
>>> user
>>>> control where the frustum and camera position are automatically
>>>> updated
>>> by
>>>> the program every cycle of the main program loop?  From what I can
>>>> tell,
>>> I
>>>> don't want to use an interactor since the user will not be interacting
>>> with
>>>> the application (the user interacts with the motion capture system,
>>>> and
>>> the
>>>> application simply queries data from the motion capture system when it
>>> is
>>>> rendering).  Again, I need to be able to create frustums that aren't
>>>> centered around the z axis.
>>>>
>>>> Thanks in advance!
>>>>
>>>> -Mark Waligora
>>>>
>>>
>>
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