Has anybody thought of adding spherical or toroidal coordinate systems
to the isosurface patch?
Just an idea.

sig.

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On Wed, 19 Jan 2000 11:55:15 +0100, Sigmund Kyrre Aas wrote:
>Has anybody thought of adding spherical or toroidal coordinate systems
>to the isosurface patch?
>Just an idea.

Spherical coordinates are already added, sort of.  As far as I know there
aren't any usable toroidal coordinate systems, because every point in 
space could be defined in two or more unique ways in such a system.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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This just got me thinking. Are the unnofficial patches using the 3.0
isosurface stuff updated manually, or are you using the one from here:
http://www.public.usit.net/rsuzuki/e/povray/iso/ ?

Just curious...

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In article <38859813.75ED1AFD@stud.ntnu.no>, Sigmund Kyrre Aas 
<as### [at] studntnuno> wrote:

> Has anybody thought of adding spherical or toroidal coordinate systems
> to the isosurface patch?
> Just an idea.

If I understand what you mean, these already exist in the form of the 
built in functions(like "R", "TH", "PH", and whatever you can make with 
the trig functions like atan()). And you can construct your own 
functions to do whatever you want, just declare them.
#declare WeirdCoordinateA = function {blahblah}
#declare WeirdCoordinateB = function {blahblah}
#declare WeirdCoordinateC = function {blahblah}

Then just use these functions as returning the coordinate values for 
your function.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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On Wed, 19 Jan 2000 09:09:01 -0500, TonyB wrote:
>This just got me thinking. Are the unnofficial patches using the 3.0
>isosurface stuff updated manually, or are you using the one from here:
>http://www.public.usit.net/rsuzuki/e/povray/iso/ ?

I updated it with the changes from that source, but it's mostly the
old 3.0 stuff.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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Ron Parker <ron### [at] povrayorg> wrote in message
news:3885c3c6@news.povray.org...
> On Wed, 19 Jan 2000 11:55:15 +0100, Sigmund Kyrre Aas wrote:
> >Has anybody thought of adding spherical or toroidal coordinate systems
> >to the isosurface patch?
> >Just an idea.
>
> Spherical coordinates are already added, sort of.  As far as I know there
> aren't any usable toroidal coordinate systems, because every point in
> space could be defined in two or more unique ways in such a system.

There are, thought they are odd.

    x =  sinh v cos phi /(cosh v -cos u)
    y =  sinh v sin phi /(cosh v -cos u)
    z =  sin u /(cosh v -cos u)

    The v = const. curves are nested tori filling all of space except for a
circle and its axis of symmetry.  u=const. are the spheres containing that
circle; and phi is the longitude, with phi=const. being halfplanes emanating
from the axis. The coordinate surfaces at any point are all orthogonal.

    Source: Schaum's math tables.

    Why anybody would want them for raytracing I don't know, but I'm sure
somebody will <grin>.

    -Robert Dawson

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I was just playing around in Maple, and made some shapes there I'd like
to use in pov. f.x:

plot3d((1.2)^x * sin(y),x=-8..Pi,y=0..Pi,coords=spherical);
(snail's house)

plot3d(y,x=0..3*Pi,y=0..3*Pi,coords=toroidal,scaling=constrained);
(ufo)

I can post images in p.b.i if you are interested.

I've found several conversion functions in my "Matematische
Formelsamlung" by Rottmann, fx for torus:
x=l*cos(phi)*sinh(ksi)/(cosh(ksi)-cos(eta))
y=l*sinh(ksi)/(cosh(ksi)-cos(eta))
z=l*sin(eta)/(cosh(ksi)-cos(eta))
I'm not sure what l is, and certainly not how to do the #declare
function {thing}.

As for the built in functions, you can only pass numbers to those, not
functions. I don't see how I can use them here.

sig.

Chris Huff wrote:
> 
> If I understand what you mean, these already exist in the form of the
> built in functions(like "R", "TH", "PH", and whatever you can make with
> the trig functions like atan()). And you can construct your own
> functions to do whatever you want, just declare them.
> #declare WeirdCoordinateA = function {blahblah}
> #declare WeirdCoordinateB = function {blahblah}
> #declare WeirdCoordinateC = function {blahblah}
> 
> Then just use these functions as returning the coordinate values for
> your function.
> 
> --
> Chris Huff
> e-mail: chr### [at] yahoocom
> Web page: http://chrishuff.dhs.org/

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Do you mean like being able to rotate functions? Such as: (x^8+y^8+z^8
rotate y*45)

If so, that would be too cool. Such a thing would be a huge help.

Sigmund Kyrre Aas wrote:

> Has anybody thought of adding spherical or toroidal coordinate systems
> to the isosurface patch?
> Just an idea.
>
> sig.

--
Samuel Benge

E-Mail: STB### [at] aolcom

Visit the still unfinished isosurface tutorial:
http://members.aol.com/stbenge

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Sigmund Kyrre Aas wrote:
> Has anybody thought of adding spherical or toroidal coordinate systems
> to the isosurface patch?
> Just an idea.

Funny you should mention that, I thought about suggesting that feature
almost at the same time as your post...

:-)

Philippe

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No, I don't mean that (see post from yesterday), and I don't quite see
the urge for such a feature. Wouldn't this do the trick?:
isosurface {
   function {}
   rotate y*45
}

ps Just visited your isotutorial, and it looks very promising! 

sig.


SamuelT. wrote:
> 
> Do you mean like being able to rotate functions? Such as: (x^8+y^8+z^8
> rotate y*45)
> 
> If so, that would be too cool. Such a thing would be a huge help.
> 
> Sigmund Kyrre Aas wrote:
> 
> > Has anybody thought of adding spherical or toroidal coordinate systems
> > to the isosurface patch?
> > Just an idea.
> >
> > sig.
> 
> --
> Samuel Benge
> 
> E-Mail: STB### [at] aolcom
> 
> Visit the still unfinished isosurface tutorial:
> http://members.aol.com/stbenge

-- 
Sigmund Kyrre Aas 
Trondheim, Norway

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