POV-Ray : Newsgroups : povray.documentation.inbuilt : Lathe and Prism updates requested by Christoph. : Re: Lathe and Prism updates requested by Christoph. Server Time
17 May 2022 20:43:08 EDT (-0400)
  Re: Lathe and Prism updates requested by Christoph.  
From: William F Pokorny
Date: 4 Jun 2016 10:10:05
Message: <5752e13d$1@news.povray.org>
On 06/03/2016 10:46 PM, Le_Forgeron wrote:
> Le 03/06/2016 23:51, William F Pokorny a écrit :
>>
>> I assume you mean flipping the handedness of the camera to right and looking at all
the test cases I created?
>>
>> It is true I ran only one of the tests posted to povray github this way(1). It
didn't change result with 3D handedness. It will take me some time to crank all the
test cases with a right hand camera & review the results.
>
> The result might be the same (actually, it should be so, as the coding of the object
remains identical), but changing the handedness, for the *same* code of the object, is
also changing the notion/visualisation of clockwise/counter-clockwise.
>

Indeed there was no change in inside vs outside determination for any 
test case using a right handed camera set up.

> Put coloured spheres at the various points used on object, using H of HSV or HSL
colour coding as the progression along the points.
> One handedness would display a clockwise progression, and the other handedness the
counter-clockwise progression.
> (you could use text item, but text would need to be oriented to be readable, less
problem with coloured spheres)
>
>

See:

http://news.povray.org/povray.binaries.images/thread/%3C5752dc4c%40news.povray.org%3E/

The viewer's perception due left versus right handed camera set ups does 
of course changes for the prism due the point set being described in the 
x,z plane, but not for the lathe due in being describe in the x,y plane.

One could say for the case of the prism, in moving to the right handed 
camera - while not changing any other scene set up - we have decided to 
look at the 2d clock face upside down. ;-)

Anyway, I understand the concern. Guess it comes to whether the wording 
Jim added in :

Note: The use of clockwise and counter-clockwise in the following 
examples should not be taken imply any notion of handedness.

enough to address it or do we need to add something more?


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