What would be the best way to make the bulge on a violin?

Nekar

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Nekar Xenos wrote:

> What would be the best way to make the bulge on a violin?
>
> Nekar

Boy, if you're using a modeller that uses patches it should be easy, but
in POV-Ray on it's own that can be difficult. I would start by declaring
the shape for the violin :

// Violin shape, very primitive
#declare Violinshape =
difference {
  union {
    cylinder { <0,0,1> <0,1,1> 1 }
    cylinder { <0,0,-1> <0,1,-1> 1 }
    }
  cylinder { <0,-0.1,0> <0,1.1,0> 1 scale <0.25,1,0.5> translate -1*x }
  cylinder { <0,-0.1,0> <0,1.1,0> 1 scale <0.25,1,0.5> translate  1*x }
 }

This should give you the basic profile, then use something like the
following:
intersection {
  object { Violinshape }
  cylinder { <0,-n,-2> <0,-n,2> n+1 }
  texture { ... }
  }

You can experiment with larger values on n (Keep n positive but keep the
negative signs). The top of the bulge will touch the plane y=1 no matter
what value you use for n.

This is untested, but this is how I would start it. You might use a
prism shape to declare the violin shape to make it more accurate.

Josh English
eng### [at] spiritonecom

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I have the vectors for the shape. Can I extrude that instead of using csg
and still do the bulge? I'll try your method just to get the hang of it. At
the moment I can't understand how an intersection with a cylinder would give
a bulge, but I'll take a deeper look into it.

Thanks

Nekar
"Joshua English" <eng### [at] spiritonecom> wrote in message
news:3AC9670C.2D6A82B6@spiritone.com...
> Nekar Xenos wrote:
>
> > What would be the best way to make the bulge on a violin?
> >
> > Nekar
>
> Boy, if you're using a modeller that uses patches it should be easy, but
> in POV-Ray on it's own that can be difficult. I would start by declaring
> the shape for the violin :
>
> // Violin shape, very primitive
> #declare Violinshape =
> difference {
>   union {
>     cylinder { <0,0,1> <0,1,1> 1 }
>     cylinder { <0,0,-1> <0,1,-1> 1 }
>     }
>   cylinder { <0,-0.1,0> <0,1.1,0> 1 scale <0.25,1,0.5> translate -1*x }
>   cylinder { <0,-0.1,0> <0,1.1,0> 1 scale <0.25,1,0.5> translate  1*x }
>  }
>
> This should give you the basic profile, then use something like the
> following:
> intersection {
>   object { Violinshape }
>   cylinder { <0,-n,-2> <0,-n,2> n+1 }
>   texture { ... }
>   }
>
> You can experiment with larger values on n (Keep n positive but keep the
> negative signs). The top of the bulge will touch the plane y=1 no matter
> what value you use for n.
>
> This is untested, but this is how I would start it. You might use a
> prism shape to declare the violin shape to make it more accurate.
>
> Josh English
> eng### [at] spiritonecom
>

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Nekar Xenos wrote:

> I have the vectors for the shape. Can I extrude that instead of using csg
> and still do the bulge? I'll try your method just to get the hang of it. At
> the moment I can't understand how an intersection with a cylinder would give
> a bulge, but I'll take a deeper look into it.

A sphere might work as well, but you'd have a harder time getting it to look
right, I think. The cylinder provides the curve of the surface, as if you were
looking down the neck of the violin towards the base, then the violinshape
object gives the form of the violin. You don't want the flat surface of a
prism, so a cylinder will have enough curve to it to simulate the bump. I'll
post some images in p.b.i to explain it a bit.

Josh

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Thanks for the help. I've never worked with cylinders, I assumed they had
flat ends as I don't have much time. There are two problems though. A
violins bulge is more like a sine wave and the sides shouldn't get thicker
at the cut-away parts. I've just thought of blobs. maybe that would work, so
I'm going to give that a try now.

Thanks

Nekar
"Joshua English" <eng### [at] spiritonecom> wrote in message
news:3AC### [at] spiritonecom...
> Nekar Xenos wrote:
>
> > I have the vectors for the shape. Can I extrude that instead of using
csg
> > and still do the bulge? I'll try your method just to get the hang of it.
At
> > the moment I can't understand how an intersection with a cylinder would
give
> > a bulge, but I'll take a deeper look into it.
>
> A sphere might work as well, but you'd have a harder time getting it to
look
> right, I think. The cylinder provides the curve of the surface, as if you
were
> looking down the neck of the violin towards the base, then the violinshape
> object gives the form of the violin. You don't want the flat surface of a
> prism, so a cylinder will have enough curve to it to simulate the bump.
I'll
> post some images in p.b.i to explain it a bit.
>
> Josh
>
>
>
>

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