This object was in the center of my pentagram, but it was too small to see.

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I like the smoothness of the objects, was this done with sphere sweeps or
sphere/cylinder unions?

How in the world do you calculate where to put each object?
I've never been able to do that, as I don't know how.

ian

Dan Johnson <zap### [at] hotmailcom> wrote in message
news:3A5### [at] hotmailcom...
> This object was in the center of my pentagram, but it was too small to
see.

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Trig nerd. ;)

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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ian mcdonald wrote:

> I like the smoothness of the objects, was this done with sphere sweeps or
> sphere/cylinder unions?
> 
> How in the world do you calculate where to put each object?
> I've never been able to do that, as I don't know how.
> 
> ian

There is only 20 spheres in that object.  I only used them where there 
was a hole in the intersection of several cylinders.  I made the spheres 
the same diameter as the cylinders so their locations are not obvious.
For your second question.  I have some books on polyhedra, and I spend 
some quality time in the analytic trigonometry section, of a calculus 
textbook.  I think I mostly just used the Pythagorean theorem though.  I 
am confident that I could make a decent looking geodesic dome with what 
I learned, but I think it would easily take me a whole day to write the 
scene file, so I have been putting it off.  I have been thinking about 
how to do it in a macro.

I made an include file with untextured versions of all of my shapes.  I 
made it for my personal use so it is not very user friendly.  If you are 
interested I will clean it up, and post it.

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Dan Johnson wrote:

> There is only 20 spheres in that object.  I only used them where there
> was a hole in the intersection of several cylinders.  I made the spheres
> the same diameter as the cylinders so their locations are not obvious.
> For your second question.  I have some books on polyhedra, and I spend
> some quality time in the analytic trigonometry section, of a calculus
> textbook.  I think I mostly just used the Pythagorean theorem though.

What is analytic trig as opposed to normal trig?
Calculus textbook?? I have been doing this exact same thing for years with
basic trig and algebra.

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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Please do. :)

Thanks,ian

Dan Johnson <zap### [at] hotmailcom> wrote in message
news:3A5### [at] hotmailcom...
> I made an include file with untextured versions of all of my shapes.  I
> made it for my personal use so it is not very user friendly.  If you are
> interested I will clean it up, and post it.
>

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> Dan Johnson wrote:
>
> > There is only 20 spheres in that object.  I only used them where there
> > was a hole in the intersection of several cylinders.  I made the spheres
> > the same diameter as the cylinders so their locations are not obvious.
> > For your second question.  I have some books on polyhedra, and I spend
> > some quality time in the analytic trigonometry section, of a calculus
> > textbook.  I think I mostly just used the Pythagorean theorem though.
>
> What is analytic trig as opposed to normal trig?
> Calculus textbook?? I have been doing this exact same thing for years with
> basic trig and algebra.
>
> --
> David Fontaine  <dav### [at] faricynet>  ICQ 55354965
> My raytracing gallery:  http://davidf.faricy.net/

I don't have any books on trig.  The calculus book has a big review section on
trig.  I took calc without ever taking trig so I had to learn trig in about a
week, while not failing any of my other classes.  As for why it was called
anylitic trig, I didn't write the book.  Maybe it means vectors.

Dan Johnson

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ian mcdonald wrote:

> Please do. :)
>
> Thanks,ian
>
> Dan Johnson <zap### [at] hotmailcom> wrote in message
> news:3A5### [at] hotmailcom...
> > I made an include file with untextured versions of all of my shapes.  I
> > made it for my personal use so it is not very user friendly.  If you are
> > interested I will clean it up, and post it.
> >

I guess include files go in the binaries.scene-files group.  I will post it
with a scene file that demonstrates all of the shapes, probably tonight or
tomorrow.
Dan

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ian mcdonald wrote:

> Please do. :)
>
> Thanks,ian
>
> Dan Johnson <zap### [at] hotmailcom> wrote in message
> news:3A5### [at] hotmailcom...
> > I made an include file with untextured versions of all of my shapes.  I
> > made it for my personal use so it is not very user friendly.  If you are
> > interested I will clean it up, and post it.
> >

Source is now in the povray.binaries.scene-files

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ian mcdonald wrote:
> How in the world do you calculate where to put each object?
> I've never been able to do that, as I don't know how.

Start with the cube.
If you draw the diagonals on each face of the cube, you get the edges of
two tetrahedra.  (Pick one!)
If you join the midpoints of the edges of each face of the tetrahedron,
you get the edges of an octahedron.
If you divide the edges of the octahedron in the golden ratio (in a
consistent way), you get the vertices of an icosahedron.

The outer dodecahedron is less easy.  You can think of it as building a
hipped roof on each face of the cube.  If the cube's vertices are




or alternately



where tau = (1+sqrt(5))/2, the golden ratio.

-- 
Anton Sherwood  --  br0### [at] p0b0xcom  --  http://ogre.nu/

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