Le_Forgeron <jgr### [at] freefr> wrote:

> > * bicubic_patch

UV coordinates are based on the patch's parametric coordinates. They stretch
with the control points. The default range is (0..1) and can be changed.

Well THERE's a teaser for you.  That should really be "...and can be changed by
....."  or followed by a link, or "see section ...."

> > * box
> > * cone, cylinder

however, keep in mind that a true cone is not a cylinder.

Well --- that's one of those ones that makes you read it over and over again,
trying to divine the import of that statement.
Did they mean "a true cylinder is not a cone"? Because I'm not sure I would have
ever thought a cone was a cylinder.
Maybe this hints at there being a technical mathematical difference between how
cylinder{} is uv-mapped vs using cone{} with 2 equal radii...   ?

> > * lathe, sor
> > * lemon
> > * mesh, mesh2
> > * ovus
> > * parametric

in this case the map is not taken from a fixed set of coordinates but the map is
taken from the area defined by the boundaries of the uv-space, in which the
parametric surface has to be calculated.

I can speculate on this, and try to imagine the true meaning, but if someone
rendered the affine transformation from <x,y,z> to <u,v> with a pattern like
cells or something, it would be a bit easier to see exactly how that happens.

Something stellar would be to see a parametric equation, and the equations used
to convert those <x,y,z>  values to the <u,v> values

> > * sphere
> > * torus

    torus: the map is taken from the area <0,0><1,1> where the u-coordinate is
wrapped around the major radius and the the v-coordinate is wrapped around the
minor radius.

Yes indeed - confirmed.  ;)

Note: Recent additions revealed torus mapping to be reversed with respect to the
u-coordinate. For backward compatibility reasons it remains the same in this
release, however this may change in the future.

This is interesting - I'll have to experiment with this and look more closely.
It's gonna be like a damned battery - where they have the negatively charged
electrons flowing out from the side labeled (+)  :|
Scientism.

> And in the sleep of the night, come the greatest question ever: why is
> the disc not part of that list ?

It's always the simple things  :D  ;)

Surface of Revolution also has special disc mapping on the end caps if the
object is not open.
Not a solution, but seems to be a potentially viable workaround.


That's an interesting and clever image map to illustrate the uv-mapping.  But
the thing that strikes me as odd there --- is that black and white checkered
stripe supposed to be on the bottom of the box like that?  Shouldn't it be all
colored gradient?



re:  the example code at the bottom of the page:

3.1.5.1 SYS File Type

The section on Output File Types refers to the 'SYS' file type as being system
specific. For the Windows implementation of POV-Ray, this system file type
equates to .BMP files (the standard windows image format). The default output
type is SYS.

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