Am 05.09.2018 um 18:12 schrieb Bald Eagle:

> I do believe that I sometimes ask one question, and you answer another.
> (And I've just noticed on an old thread that sometimes I can read the same
> question in one of two ways, and the ambiguity of the meaning even makes ME
> interpret it differently the second time I read it and respond to a reply.)

That may well happen ;)

> For bicubic patches the UV coordinates can be specified for each of the four
> corners of the patch. This goes right before the control points.
> The syntax is:
> 
>   uv_vectors <corner1>,<corner2>,<corner3>, <corner4>
> with default
>   uv_vectors <0,0>,<1,0>,<1,1>,<0,1>
> 
> "The default range is (0..1) and can be changed...."
> 
> There is no "explanation" that you refer to.
> For me, an explanation would be along the lines of changing those uv vectors and
> showing the effect it has on how a unit-square texture gets mapped on it.

Technically, that would not be an explanation, but an example.

> Then you add "scale" into the mix, and it can be pretty unclear - unless you
> ALREADY know what's going on and you're reading the documentation
> "retroactively", in hindsight, which I think is what often happens when some of
> the docs get written or referred to.

You're right in that the docs on POV-Ray's UV mapping implementation
apparently presume the user is already familiar with the concept of UV
mapping.

For a person familiar with the concept, I think it is pretty
self-evident what `uv_vectors` does.

Note that you're looking at the reference section, not a tutorial. I
think it is legitimate to expect the reference section's reader to be
already familiar with common 3D graphics concepts; UV mapping is one of
those.


Of yourse you may rightly claim that adding an in-depth explanation of
UV mapping, with examples and all, to the _tutorial_ would do the docs
some good. I wouldn't argue with that; currently all we have is a
section on UV mapping in mesh2.


> "Look, newbie - the docs say exactly that, and we're all telling you that the
> text isn't inconsistent with what happens..."
> Very technically correct in highly qualified courtroom attorney-shyster
> legalese, but of no use to the first-time, or even sometimes the tenth-time or
> hundredth-time reader.

"I failed to understand this documentation, so I turn to complaining
about the documentation" - also a not too uncommon and not too helpful
schtick.

There is certainly a point to it when the person is an average member of
the target audience, because it may be an indication that the
documentation is indeed missing its audience. Hoever,

(a) that point is moot if the person isn't a member of the target
audience in the first place (because the document in question presumes
certain background knowledge) or is the only person who happens to not
get this part of the documentation, and

(b) if what you really want is an explanation (as opposed to a
discussion about whether the docs are good or not), don't complain about
the docs; rather, ASK FOR AN EXPLANATION.

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