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I remember seeing splines as objects, perhaps in Chris Colefax's include
file. It's not just a means of decribing points but an "object."
What kind of pov primitive is that: sphere sweep, bicubic, etc.
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On Tue, 17 Sep 2002 13:53:47 -0400, "Greg M. Johnson" <gregj:-)565### [at] aol com>
wrote:
> What kind of pov primitive is that: sphere sweep, bicubic, etc.
Spline is in general vector function (in POV 2D-5D). It's equations base on
set of points. Just like you have function based primitives you can spline
based primitives. There is whole chapter about it in documentation.
ABX
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I read the docs but thought someone had a utility that make "visible"
splines.
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On Tue, 17 Sep 2002 14:17:29 -0400, "Greg M. Johnson" <gregj:-)565### [at] aolcom>
wrote:
> I read the docs but thought someone had a utility that make "visible"
> splines.
There is no "visible" spline. There are only spline based objects. Examples of
splines "visible" this way are in sample docs. You have to precise what you
want to make visible.
ABX
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Has anyone else looked at Chris Colefax's spline include file?
http://www.geocities.com/ccolefax/spline/index.html
Is his
preview_spline (MySpline, default_options)
simply a sphere sweep?
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> Is his
> preview_spline (MySpline, default_options)
> simply a sphere sweep?
Don't confuse Chris Colefax's spline include file with POV-Ray 3.5 splines.
The include file was written well before splines were brought into POV-Ray,
so it doesn't make any use of them at all.
The preview_spline macro does not use sphere sweeps, though it may simulate
them. If you want the 3.5 equivalent of that macro, then use a sphere_sweep.
Unfortunately, POV-Ray has no way to apply a separarely defined spline to a
sphere_sweep object. Nor can it apply a separate spline to a prism object or
something of that sort. I think this is a weakness in POV-Ray - it has the
same data structure represented in different ways depending on what you're
using it for.
I understand that the data structures aren't *identical*, but they're darn
similar and would be much more powerful if they were more portable.
- Slime
[ http://www.slimeland.com/ ]
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Slime wrote:
> <snip>
>
> Unfortunately, POV-Ray has no way to apply a separarely defined spline to
> a sphere_sweep object. Nor can it apply a separate spline to a prism
> object or something of that sort. I think this is a weakness in POV-Ray -
> it has the same data structure represented in different ways depending on
> what you're using it for.
>
> I understand that the data structures aren't *identical*, but they're darn
> similar and would be much more powerful if they were more portable.
Something vaguely related that came to my mind: Is it possible with the
current tools to define a sort of hybrid between a lathe and a prism? I
mean: in a prism you specify the section with a spline, in a lathe you
specify the generatrix (is that the word?) with a spline, what about
specifying both? In case it isn't possible (as I guess), wouldn't it be
cool to have this kind of objects (lathes with non-circular section /
prisms with non-linear sweeps)? Just an idea, though.
Greetings
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"Jellby" <jel### [at] M-softhomenet> wrote in message
news:3d87a619@news.povray.org...
> Something vaguely related that came to my mind: Is it possible with the
> current tools to define a sort of hybrid between a lathe and a prism? I
> mean: in a prism you specify the section with a spline, in a lathe you
> specify the generatrix (is that the word?) with a spline, what about
> specifying both? In case it isn't possible (as I guess), wouldn't it be
> cool to have this kind of objects (lathes with non-circular section /
> prisms with non-linear sweeps)? Just an idea, though.
>
I've used this before in Imagine 2 on the amiga (where is was called
'Forms') and I think it will have to become my new project while I wait for
inspiration on the current IRTC topic
jim
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Jellby <jel### [at] m-softhomenet> wrote:
> Something vaguely related that came to my mind: Is it possible with the
> current tools to define a sort of hybrid between a lathe and a prism? I
> mean: in a prism you specify the section with a spline, in a lathe you
> specify the generatrix (is that the word?) with a spline, what about
> specifying both? In case it isn't possible (as I guess), wouldn't it be
> cool to have this kind of objects (lathes with non-circular section /
> prisms with non-linear sweeps)? Just an idea, though.
It shouldn't be too difficult to make a macro which creates that kind
of surface as a mesh using the two splines. (It would probably render 10
times faster as a mesh, as well.)
--
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -
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in news:3d87a619@news.povray.org Jellby wrote:
> Is it possible with the
> current tools to define a sort of hybrid between a lathe and a prism?
http://www.econym.demon.co.uk/isotut/splines.htm
prismatic lathe
Ingo
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