clipka <ano### [at] anonymousorg> wrote:
> Am 03.05.2016 um 02:34 schrieb Bald Eagle:
>
> > Oh, see - what I was thinking was that the WHOLE curve would be processed in
> > context, which would not lead to your second scenario, but to:
> >
> >>     A    B
> >>   + |\  /|
> >>   __| \/ |_____axis
> >
> > Which ought to give the same as your first scenario, no?
>
> That may be what you were thinking, but it's not what happens. It's
> simply not how POV-Ray works internally.

I guess I was speaking about the initial "spline" that then gives rise to the
shape that is enclosed by its rotation about the axis.  If you first example
were caught by the parser, corrected to the above, and THEN the rest of
POV-Ray's internals were let loose on it....

I suppose I'll just bow out since I don't have the source code / flowchart in
front of me.  ;)

> It's not like POV-Ray iterates over all the points on an object's
> surface and shoves each into the image, so that it could just shuffle
> around points arbitrarily in 3D space as it goes along.
>
> What POV-Ray instead does is that it iterates over all the points in the
> result image, computes the line in 3D space that is projected onto that
> point in the image, and then essentially solves a mathematical equation
> to figure out all the points at which that line intersects any given
> object in the scene.
>
> Now if POV-Ray finds a point on a lathe, it is too late to do any
> rotation by 180 degrees -- because the resulting point will most likely
> not be on the line anymore.

Fully understood. I didn't imagine that's the way it worked.

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