In article <3904F7A6.AF260EC3@hotmail.com>, Tor Olav Kristensen 
<tor### [at] hotmailcom> wrote:

> So it is the "ciagar" shape that messes up the 
> reflections. 
> 
> That's a pity. =(
> 
> Is this to be considered as a bug ? 
> 
> And if so, do you know if the other people you 
> mentioned have posted a bug report on the subject?
> 
> I have also noticed that this shape is hollow. 
> And therefore it doesn't behave in CSG operations.

I think the reason you end up with a "cigar" shape at all is a bug. As I 
recall, this is because the bounding gets messed up by the radius 
settings, I think someone was working on a fix for it...which wouldn't 
give a cigar shape, but the actual torus shape.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
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Chris Huff wrote:
> 
> I think the reason you end up with a "cigar" shape at all is a bug. 

As far as I remember you do get the torus shape if you do not 
subtract it from another shape.

Btw: Are there other shapes that intersects with themselves 
like this? 

(Maybe one could introduce a new "self_intersection" keyword ? :)

> As I recall, 
> this is because the bounding gets messed up by the radius
> settings, I think someone was working on a fix for it...which wouldn't
> give a cigar shape, but the actual torus shape.

But, but, but ... 
...How are we supposed to model such cigar shapes then?

(Scaling a sphere along an axis gives a shape that's round 
at the ends, while this cigar shape ends in a sharp point.)

Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html

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Tor Olav Kristensen wrote:

> But, but, but ...
> ...How are we supposed to model such cigar shapes then?

A lathe can do it with ease and can also be used in CSG operations.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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In article <390516B5.CA6D79B1@pacbell.net>, lin### [at] povrayorg 
wrote:

> Tor Olav Kristensen wrote:
> 
> > But, but, but ...
> > ...How are we supposed to model such cigar shapes then?
> 
> A lathe can do it with ease and can also be used in CSG operations.

You can also do it with the poly or quartic objects, and it is quite 
easy to do with the isosurface object.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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On Mon, 24 Apr 2000 20:53:25 -0700, Ken <tyl### [at] pacbellnet> wrote:
>
>Tor Olav Kristensen wrote:
>
>> But, but, but ...
>> ...How are we supposed to model such cigar shapes then?
>
>A lathe can do it with ease and can also be used in CSG operations.

 I have been having exactly the same problem with the chimney of a loco that I
am modelling.  I was using a cone with the fillet radii being produced by the
outside surface of two tori.  These fillets have a different texture to the rest
of the chimney, presumably because of the normal being the wrong way.

A lathe object should solve this problem, but at the expense of a much more
involved definition requiring a bezier_spline definition.
David
dav### [at] hamiltonitecom
http://www.hamiltonite.com/

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David Wilkinson wrote:

> A lathe object should solve this problem, but at the expense of a much more
> involved definition requiring a bezier_spline definition.

This is one of the areas where I will always used an external utility.
Hand coding splines is a waste of time when you can use a utility to
simply point and click your shape definition.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken wrote:
> 
> Tor Olav Kristensen wrote:
> > ...How are we supposed to model such cigar shapes then?
> 
> A lathe can do it with ease and can also be used in CSG operations.

Thank you. I did not think of that.

(But it would still be nice to have a basic shape like
this one. Because then I wouldn't have to calculate 
the co ordinates for the appropriate quadratic_spline or
cubic_spline.)

Btw.: Will such a lathe render slower than my "cigar" shape ?

Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html

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Chris Huff wrote:
> 
> Ken wrote:
> 
> > Tor Olav Kristensen wrote:
> > > ...How are we supposed to model such cigar shapes then?
> >
> > A lathe can do it with ease and can also be used in CSG operations.
> 
> You can also do it with the poly or quartic objects, and it is quite
> easy to do with the isosurface object.

I have been thinking about that, but I have not found the 
proper equation for that yet. 

(Where the minor and major radii are a part of the equation.)

Any suggestions?

And would it be possible to use a quartic object (and an 
isosurface) in a CSG expression?

Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html

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David Wilkinson wrote:
> >
> Ken wrote:
> >
> >Tor Olav Kristensen wrote:
> >> ...How are we supposed to model such cigar shapes then?
> >
> >A lathe can do it with ease and can also be used in CSG operations.
> 
>  I have been having exactly the same problem with the chimney of a loco that I
> am modelling.  I was using a cone with the fillet radii being produced by the
> outside surface of two tori.  These fillets have a different texture to the rest
> of the chimney, presumably because of the normal being the wrong way.
> 
> A lathe object should solve this problem, but at the expense of a much more
> involved definition requiring a bezier_spline definition.

Do you have any suggestions on how to calculate a set of co-ordinates
for a bezier_spline lathe that models such a "cigar" accurately?

Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html

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Ken wrote:
> 
> David Wilkinson wrote:
> 
> > A lathe object should solve this problem, but at the expense of a much more
> > involved definition requiring a bezier_spline definition.
> 
> This is one of the areas where I will always used an external utility.
> Hand coding splines is a waste of time when you can use a utility to
> simply point and click your shape definition.

But I can not tell my macros to go and use an external utility...

... Or can I ? :)

Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html

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