In article <3A5C93DC.76B86BCE@free.fr> , Nicolas Calimet <pov### [at] freefr>
wrote:

>> No, it is a design issue.  POV-Ray cannot know if focal blur will be enabled
>> in a later frame as it reparses the scene each time.
>
>  This is something I can't understand. The purpose of reparsing the
> scene for each frame is especially to be able to change objects/variables/
> parameter between frames. With some #if(clock) condition, it should be
> possible to turn on and off focal blur or anything else from frame to frame.

Antialiasing is a command line option.  You cannot set it in a scene because
it has nothing to do with a scene.

>> However, it cannot
>> know if antialiasing was on or off once it has been turned off automatically
>> after focal blur has been used.
>
>  This could be avoided if focal blur was not reverting specific internal
> variables...

Correct.  A redesign of POV-Ray is necessary to remove all these global
variables - that is what will POV-ray 4.0 will be.

>> Practically using focal blur together with
>> antialiasing is illegal, so it has to do something.
>
>  Again something I don't understand: why "illegal" ?

"Illegal" by specification.  There are still reasons (I hope), but I never
looked into the antialiasing code to say why exactly.

>> I agree that the
>> "something" is not logical, but turing on and off focal blur in different
>> frames is simply a very rare case, so nobody ever noticed this missing
>> feature...
>
>  But it would speed up a lot to turn focal blur off when the effect
> is neglectible. For now, I suppose people manage it by starting a new render,
> even if the animation is following the same "scene" (no change in camera
> viewpoint for instance).

Well, the whole problem is based on the ten year development.  You don't
have the same problem with POV-Ray 2.2 because it does not support an
internal render loop.  You can still revert to this behaviour in 3.1 by only
setting the clock and render individual frames, as you suggested.

>  Okay, I don't flame the current behaviour. It was just my opinion
> of what could be easily implemented ;-)

Understood, but keep in mind that something that sounds easy may not always
be as easy as you think at first sight...


    Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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