On 06/04/2016 04:39 PM, Le_Forgeron wrote:
> Le 04/06/2016 15:48, William F Pokorny a écrit :
>> Left vs Right camera views of lathe and prism points image for
povray.documentation.inbuilt discussion.
>>
>> Bill P.
>
> There is a problem with the prism texture : the lower face is of interior_texture
for the counterclockwise prism
>
> In attached pictures: prism was not clipped, lathe was clipped.
>
> And the notion of clockwise is a 3D thing which might still be reworded, something
along: globally, for successive points, compared to the center of all points, when
positive y values decreases, the positive x values increases (?)
>
>
> right handed system is not only swapping the Z direction, but more often based on Z
being the elevation.
>

Why are you showing the axis rotations for both xy and xz for the 
prisms? The prism object splines are defined in the xz plane(1) :

http://wiki.povray.org/content/Reference:Prism

"...This is followed by the specified number of 2-D vectors which define 
the shape in the x-z plane."

The prism sweep is in y.

I understand in the right handed system Z is usually treated as up.

Bill P.

(1) - The underlying spline mechanism is perhaps still evaluated inside 
the code as x,y - not sure.

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