I need to create spiral images for spiral-carved table legs etc. I have
discovered that it can be done using the sphere sweep modification to
PovRay. I'm slightly wary though.

TMPov can do sphere sweeps but it is unsupported by the PovRay team. I can
get C code to compile my povray to use sphere sweeps, but there is a
problem.

No offence, but I don't want to wreck my current povray installation by
converting it to something which a) is unsupported, and b) I will lose next
time a version comes out....

To this end is there any way to create such objects without modifying
Povray, possibly via triangle-patchs properly modelled. I have SPatch, and
Moray, but though they both do rotational sweeps, neither of them consider
that a translation might be required.


Can anyone suggest some software to supply povray/moray with the object I'm
looking for, or if not, is there any way of faking it?

Yours hopefully,


Andrew Ratcliffe
ara### [at] aratcliffedemoncouk

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This is more of a question than an answer.  Can TMPov just be used with the
modified pvengine.exe like the isosurface patch?  If so, then you could run it
from a different directory without touching your current installation.  All the
preferences will be the same.  That's the way I use the iso surface patch and
haven't had a problem.

A Ratcliffe wrote:

> I need to create spiral images for spiral-carved table legs etc. I have
> discovered that it can be done using the sphere sweep modification to
> PovRay. I'm slightly wary though.
>
> TMPov can do sphere sweeps but it is unsupported by the PovRay team. I can
> get C code to compile my povray to use sphere sweeps, but there is a
> problem.
>
> No offence, but I don't want to wreck my current povray installation by
> converting it to something which a) is unsupported, and b) I will lose next
> time a version comes out....
>
> To this end is there any way to create such objects without modifying
> Povray, possibly via triangle-patchs properly modelled. I have SPatch, and
> Moray, but though they both do rotational sweeps, neither of them consider
> that a translation might be required.
>
> Can anyone suggest some software to supply povray/moray with the object I'm
> looking for, or if not, is there any way of faking it?
>
> Yours hopefully,
>
> Andrew Ratcliffe
> ara### [at] aratcliffedemoncouk

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Mike Hough wrote in message <35843528.61366DA2@aol.com>...
>This is more of a question than an answer.  Can TMPov just be used with the
>modified pvengine.exe like the isosurface patch?  If so, then you could run
it
>from a different directory without touching your current installation.  All
the
>preferences will be the same.  That's the way I use the iso surface patch
and
>haven't had a problem.
>


Yep. Just name it differently, is all. =)

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For spirals, you might check out the nice little OpenGL freeware program
called "Helixir" at http://www.evolve.co.uk/helixir/

Norm Krumpe

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try:
using sheres in a #while loop translate  a sphere out to the radius of a
leg in the z direction
rotate by a amount of degrees(experiment)
translate up by a small amount in the y direction
repeat

If you want some sample code contact me 
at mic### [at] virginnet

A Ratcliffe <ara### [at] aratcliffedemoncouk> wrote in article
<6lve78$67f$1@oz.aussie.org>...
> I need to create spiral images for spiral-carved table legs etc. I have
> discovered that it can be done using the sphere sweep modification to
> PovRay. I'm slightly wary though.
> 
> TMPov can do sphere sweeps but it is unsupported by the PovRay team. I
can
> get C code to compile my povray to use sphere sweeps, but there is a
> problem.
> 
> No offence, but I don't want to wreck my current povray installation by
> converting it to something which a) is unsupported, and b) I will lose
next
> time a version comes out....
> 
> To this end is there any way to create such objects without modifying
> Povray, possibly via triangle-patchs properly modelled. I have SPatch,
and
> Moray, but though they both do rotational sweeps, neither of them
consider
> that a translation might be required.
> 
> 
> Can anyone suggest some software to supply povray/moray with the object
I'm
> looking for, or if not, is there any way of faking it?
> 
> Yours hopefully,
> 
> 
> Andrew Ratcliffe
> ara### [at] aratcliffedemoncouk
> 
> 
> 
>

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Norm Krumpe wrote:

> For spirals, you might check out the nice little OpenGL freeware program
> called "Helixir" at http://www.evolve.co.uk/helixir/

The homepage looks nice, but the program is Win-only unless
they release the source and somebody hacks it to work with
Mesa.

From the original question I guess that aratcliffe
meant helixes, not spirals (Helixir does both).

Here is a trick I tried: Take a torus, cut it into sectors,
and shear each sector (using "Matrix", doing y += c*x)
a little, and shift adjacent sectors up so that they match.

The math is easy (the formulas fit on a single page).
The problem with this method is that shearing distorts the
cross section of the torus into ellipses, and adjacent 
ellipses don't match exactly, which becomes visible unless
the sectors are very short and the material is rough.

Ralf

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On Fri, 16 Apr 1999 02:37:56 +0200, Ralf Muschall
<rmu### [at] t-onlinede> wrote:

>Here is a trick I tried: Take a torus, cut it into sectors,
>and shear each sector (using "Matrix", doing y += c*x)
>a little, and shift adjacent sectors up so that they match.
>
>The math is easy (the formulas fit on a single page).
>The problem with this method is that shearing distorts the
>cross section of the torus into ellipses, and adjacent 
>ellipses don't match exactly, which becomes visible unless
>the sectors are very short and the material is rough.

You do realize you're replying to a post from almost a year ago,
right? 

Anyway, one nice quick-and-dirty way to do spring-like things is to
use my spring.inc file, from http://www2.fwi.com/~parkerr/traces.html
There are of course other springs out there, but I'm irrationally
attached to mine.  It cuts the toruses into quarters, then rotates
them in such a way as to make a continuous (well, C1 anyway) helix.

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