On 05/11/2017 09:09, Stephen wrote:
> Reposting this so I can pick it up in thunderbird.
> 
> (It came through the first time blank.)
> 
> 
> "cbpypov" <nomail@nomail> wrote:
>> Stephen <mca### [at] aolcom> wrote:
>>
>>>
>>> Oops! I forgot the beginnings of this thread.
>>> That's what he said in the first post. But the third one with an
>>> attachment still says:
>>>
>>>> // You can only use screen.inc with the perspective camera. Screen.inc
>>>> // will automatically create the camera definition for you when it is
>>>> // included.
>>>
>>
>> No need to remember it: it's there, online, you can read it again ;) But I think
>> you copied these lines from its screen.inc attachment. BUT, these lines are
>> there because SharkD copied them from the original screen.inc and frogot to
>> delete them :D Maybe it's me: but I am sure this thread would not be here if
>> SharkD did not have tried to get ortho-cam to work. Moreover, his
>> reimplementation of Set_Camera would not have a new `orth` parameter:
>>
>>      #macro Set_Camera(Location, LookAt, Angle, Ortho)
>>
>> Right?
>>

Hands up for posting without validating. :-(


>> So, ... we are a bit at cross-purposes, i think. I attached examples of a
>> minimal scene. minimal_perspective.pov uses the normal camera, and using
>> screen.inc (minimal_screen.pov) gives identical results. When setting the
>> ortho-cam in the traditional way, I get the expected result (minimal_ortho.pov).
>> However, when using SharkD's screen.inc and setting `ortho=on`), the result is
>> way different (minimal_ortho_screen.pov). I think this is not how it is supposed
>> to work, i.e. minimal_ortho.png and minimal_ortho_screen.png are supposed to be
>> identical, but they are not.
>>

You are right. I imported a couple of the scenes into Bishop3D, to get a 
visual representation of the cameras.
Adjusting the Up and Right Vectors of the orthogonal camera until the 
"look at" areas coincided. The angle I read back was 66.67. Substituting 
that into  minimal_ortho_screen.pov it was out by a factor of 2. an 
angle of 66.67/2 gave me a very similar image to minimal_perspective.pov


I conclude that there is something not right with the way that 
screen_ortho.inc converts angle into the the other vectors.

Finding what is beyond me.I would be still at it when the cows came home.



>>>
>>> There will be a tangent in there some way.
>>>
>>>
https://en.wikipedia.org/wiki/Angle_of_view#Derivation_of_the_angle-of-view_formula
>>>
>>> All those hard quantum sums, eh? ;-)
>>>
>>
>> I see, it should be simple ;) I tried it, see minimal_ortho_fake.pov. But it is
>> still wrong :/
>>

I had a quick look at it and it is beyond me. I'm afraid.



-- 

Regards
     Stephen

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