One of the commands I use the most when I'm working in 3D CAD applications
such as Solid Edge, AutoCAD, or MicroStation is the one that generates a
solid object by sweeping a closed shape along a path.  Very often when I'm
thinking of modelling something in POV I wish for such a command.  I have
read and re-read the POV documentation and can't find an analogous
constuction.  The closest thing seems to be the sphere sweep, but unless
you want a circular crossection this doesn't seem to be much use.  Am I
missing something?

I realize that if I want to follow a path of straight line tangent segments
and arcs I can assemble a series of prism and partial lathe objects, but
unless there's an existing macro for that it seems fairly laborious.  Does
anyone know of such a macro?  Also, it seems to me that if there are any
'kinks' in the path, assembling pieces like this won't work well either.

Comments and suggestions welcomed.

Thanks,
Sun.

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Hi SunTzu,

I had the same problem as well, when trying to make the ears of some mugs.
The cross-section was an union of two (half-)elipses.

> I realize that if I want to follow a path of straight line tangent
segments
> and arcs I can assemble a series of prism and partial lathe objects

thats how I solved it, the results are pretty good, as long as you don't
make the object transparant.

> Also, it seems to me that if there are any
> 'kinks' in the path, assembling pieces like this won't work well either.

this is another problem indeed.

So, I can't help you with a nice solution, but I can send you the code used
for the ears of the mugs if you like?

Greetings,

JWV

"SunTzu2" <sun### [at] hotmailcom> wrote in message
news:web.40882e93ffb86f20eba257cf0@news.povray.org...
> One of the commands I use the most when I'm working in 3D CAD applications
> such as Solid Edge, AutoCAD, or MicroStation is the one that generates a
> solid object by sweeping a closed shape along a path.  Very often when I'm
> thinking of modelling something in POV I wish for such a command.  I have
> read and re-read the POV documentation and can't find an analogous
> constuction.  The closest thing seems to be the sphere sweep, but unless
> you want a circular crossection this doesn't seem to be much use.  Am I
> missing something?
>
> I realize that if I want to follow a path of straight line tangent
segments
> and arcs I can assemble a series of prism and partial lathe objects, but
> unless there's an existing macro for that it seems fairly laborious.  Does
> anyone know of such a macro?  Also, it seems to me that if there are any
> 'kinks' in the path, assembling pieces like this won't work well either.
>
> Comments and suggestions welcomed.
>
> Thanks,
> Sun.
>
>
>
>
>

Post a reply to this message

On Thu, 22 Apr 2004 16:46:33 EDT, "SunTzu2" <sun### [at] hotmailcom> wrote:
> Comments and suggestions welcomed.

See bottom of http://www.econym.demon.co.uk/isotut/more.htm

HTH, ABX

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ABX <abx### [at] abxartpl> wrote:
> On Thu, 22 Apr 2004 16:46:33 EDT, "SunTzu2" <sun### [at] hotmailcom> wrote:
> > Comments and suggestions welcomed.
>
> See bottom of http://www.econym.demon.co.uk/isotut/more.htm
>

Thank you.  My first impression (after about 2 minutes looking at the code)
is that I don't understand what the 'waist' parameter is for in the
'sweepspline' macro.  If you know I'd appreciate it if you could tell me,
otherwise I'll just play with it when I get home from work and try and
figure it out.

Sun.

Post a reply to this message

On Fri, 23 Apr 2004 09:27:26 EDT, "SunTzu2" <sun### [at] hotmailcom> wrote:
> Thank you.  My first impression (after about 2 minutes looking at the code)
> is that I don't understand what the 'waist' parameter is for in the
> 'sweepspline' macro.  If you know I'd appreciate it if you could tell me,
> otherwise I'll just play with it when I get home from work and try and
> figure it out.

I never used this macro but as far as I understand description:

Waist  A spline with x coordinates that specify the radius of the spheresweep
       The secion of the spline between control points 0 and 1 will be used

it is characteristic how radius changes along base spline. So Basically
writing it this way:

My_Waist = spline { linear_spline 0 , 0 , 1 , 2 } 

means for me that at the begioning sweeped shape is as minimal as possible :-)
(nothing/point/vertex) and at the end of sweeping it is twice large as
designed. But as I said I never used that macro.

ABX

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in news:web.40882e93ffb86f20eba257cf0@news.povray.org SunTzu2 wrote:

> One of the commands I use the most when I'm working in 3D CAD
> applications such as Solid Edge, AutoCAD, or MicroStation is the one
> that generates a solid object by sweeping a closed shape along a
> path. 

I posted an extruder/lofter by Daniele Varrazzo in:

Newsgroups: povray.binaries.utilities
Subject: Striscia, extruder/lofter
From: ingo <ing### [at] tagpovrayorg>
Message-ID: <Xns94D4AF6BE46A0seed7@news.povray.org>
Date: 23 Apr 2004 11:15:11 -0400
Xref: news.povray.org povray.binaries.utilities:3720

It is completely SDL based and doesn't use the since 3.5 built in splines.


Ingo

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