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From: Reuben Pearse
Subject: What does the UV in uv_mapping stand for?
Date: 8 Mar 2001 12:24:00
Message: <3aa7c030@news.povray.org>
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Hi all,
Just wondering what the "UV" in uv_mapping stands for?
Ultra-violet?
Upper Volumetrics?
Under valued?
Utter vagueness?
Thanks
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Reuben Pearse wrote:
>
> Hi all,
>
> Just wondering what the "UV" in uv_mapping stands for?
>
To put it bluntly: UV surface is parametric surface, which is decribed
as function of 2 parameters: u and v. I.e. each point on surface is
calculated as result of some function:
x=fx(u,v);
y=fy(u,v);
z=fz(u,v);
usually u and v run from 0 to 1 (but they could take other values as
well). Put u and v values to functions and you can calculate each point
on surface.
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They aren't the initials of any particular words.
My guess is that they were just taken from the alphabet.
They describe coordinates in a curved 2D space.
The letters were chosen by moving from z toward a.
Since x, y and z have been used, for the standard 3D
coordinates, someone decided upon u and v. Don't know
what dimension w is used for...
z,y,x,(w),u,v,
Harold
"Reuben Pearse" <reu### [at] presence-systems com> wrote in message
news:3aa7c030@news.povray.org...
> Hi all,
>
> Just wondering what the "UV" in uv_mapping stands for?
>
> Ultra-violet?
> Upper Volumetrics?
> Under valued?
> Utter vagueness?
>
> Thanks
>
>
>
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On Thu, 8 Mar 2001 13:29:56 -0800, Harold Baize wrote:
>They aren't the initials of any particular words.
>My guess is that they were just taken from the alphabet.
>They describe coordinates in a curved 2D space.
>The letters were chosen by moving from z toward a.
>Since x, y and z have been used, for the standard 3D
>coordinates, someone decided upon u and v. Don't know
>what dimension w is used for...
It's the parametric mapping equivalent of z, just as u and v are the
parametric mapping equivalents of x and y.
--
Ron Parker http://www2.fwi.com/~parkerr/traces.html
My opinions. Mine. Not anyone else's.
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Vahur Krouverk wrote:
> usually u and v run from 0 to 1 (but they could take other values as
> well). Put u and v values to functions and you can calculate each point
> on surface.
Nah, usually 0 to 2pi ;)
--
David Fontaine <dav### [at] faricynet> ICQ 55354965
My raytracing gallery: http://davidf.faricy.net/
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Harold Baize wrote:
> They aren't the initials of any particular words.
> My guess is that they were just taken from the alphabet.
> They describe coordinates in a curved 2D space.
> The letters were chosen by moving from z toward a.
> Since x, y and z have been used, for the standard 3D
> coordinates, someone decided upon u and v. Don't know
> what dimension w is used for...
>
> z,y,x,(w),u,v,
Vectors in computer graphics are often represented with 4 coordinates -
w, x, y, and z. This allows you to have a 4x4 transformation matrix
that can not only rotate and scale the coordinates but also perform
translations and perspective projections. The resulting 4D vector
[w,x,y,z] must be transformed into the 3D vector [x/w, y/w, z/w]. All
this to say that the 'w' was reserved.
David Buck
dav### [at] simberoncom
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