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"the world is flat!" exclaimed Louis Wu when he set foot on the Ringworld
for the first time. And indeed it is. This is a fast construction in Moray
of the Ringworld, exactly to scale, but without the Shadow Squares and
without atmosphere or landscaping. The Rim Walls are hardly visible in the
distance. During day light, the world and atmophere would seem flat, the
Arch of Heaven being hidden.
Thomas
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Download 'ringworld_02.jpg' (9 KB)
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"Thomas de Groot" <t.d### [at] inter nlnet> wrote:
> "the world is flat!" exclaimed Louis Wu when he set foot on the Ringworld
> for the first time. And indeed it is. This is a fast construction in Moray
> of the Ringworld, exactly to scale, but without the Shadow Squares and
> without atmosphere or landscaping. The Rim Walls are hardly visible in the
> distance. During day light, the world and atmophere would seem flat, the
> Arch of Heaven being hidden.
According to my calculations, the rim walls would have an angular size of
about 7 minutes of arc, viewed from the middle of the Ring. With atmosphere
and landscape, all but invisible.
I find it mildly annoying that, from its surface, the Ringworld would look
no more exciting than a flat earth! One would only get a true sense of
scale and spectacle from hundreds of miles in the air...
Bill (secretly building a Dyson sphere in his garden shed)
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This is a version with clouds, but without atmospheric haze (that's more
difficult!!!).
Next: Shadow Squares.
Thomas
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"Bill Pragnell" <bil### [at] hotmailcom> schreef in bericht
news:web.435e28311389c621731f01d10@news.povray.org...
>
> According to my calculations, the rim walls would have an angular size of
> about 7 minutes of arc, viewed from the middle of the Ring. With
atmosphere
> and landscape, all but invisible.
>
That's correct. In "Ringworld", the party is just able to see them because
they are on the (lower) slope of Fist of God, according to the map in
"Ringworld Engineers", about 60 miles above the big ocean.
> I find it mildly annoying that, from its surface, the Ringworld would look
> no more exciting than a flat earth! One would only get a true sense of
> scale and spectacle from hundreds of miles in the air...
>
It's an absolutely boring view! ;-)
However, at night, that would be gorgeous.
> Bill (secretly building a Dyson sphere in his garden shed)
>
Wow!!!
Thomas
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"Thomas de Groot" <t.d### [at] internlnet> wrote:
> > Bill (secretly building a Dyson sphere in his garden shed)
> Wow!!!
It's a big shed.
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... and now with Shadow Squares.
The greenish clouds are an effect of radiosity.
Thomas
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"Thomas de Groot" <t.d### [at] internlnet> wrote:
> ... and now with Shadow Squares.
> The greenish clouds are an effect of radiosity.
That's really good. I think it looks better than anything I managed. I might
have to dig out my code - we can have a Ring-off!
One point, however: to my mind, the shadowed areas of the arch should be the
same colour as the sky - just like the shadowed areas of the moon in our
sky during daylight. The lit areas of the ring would probably not cast that
much light - certainly less than the earthlight cast onto the moon.
Otherwise, keep 'em coming!
Bill
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Thomas de Groot nous apporta ses lumieres en ce 2005-10-26 08:24:
> ... and now with Shadow Squares.
> The greenish clouds are an effect of radiosity.
>
> Thomas
>
>
>
Needs an area_light. In all the ilustrations I saw, the shadows have soft edges.
--
Alain
-------------------------------------------------
Drive A: not responding.. .Formating C: instead
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Alain <ele### [at] netscapenet> wrote:
> Needs an area_light. In all the ilustrations I saw, the shadows have soft edges.
I have a feeling that soft terminators would not be visible on the arch to
the naked eye - too small. It's likely that Ringworld illustrations are
exaggerated for artistic effect.
I could be wrong - I *think* I used an area_light for my ringworld picture
(see previous thread) but I can't remember! :)
Bill
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Bill Pragnell nous apporta ses lumieres en ce 2005-10-26 12:26:
> Alain <ele### [at] netscapenet> wrote:
>
>>Needs an area_light. In all the ilustrations I saw, the shadows have soft edges.
>
> I have a feeling that soft terminators would not be visible on the arch to
> the naked eye - too small. It's likely that Ringworld illustrations are
> exaggerated for artistic effect.
>
> I could be wrong - I *think* I used an area_light for my ringworld picture
> (see previous thread) but I can't remember! :)
>
> Bill
>
In the images I saw, the shadowing squares are between 1/2 and 2/3 of the ring's
radius. With such
proportions, you have prety whide penumbraes.
--
Alain
-------------------------------------------------
To the world you may be one person, but to one
person you may be the world.
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"Alain" <ele### [at] netscapenet> schreef in bericht
news:43603cc3$1@news.povray.org...
> >
> In the images I saw, the shadowing squares are between 1/2 and 2/3 of the
ring's radius. With such
> proportions, you have prety whide penumbraes.
>
According to Larry Niven, in Ringworld, the shadow squares are 1x10^6 by
2.5x10^6 miles big, and orbit the sun at about 12x10^6 miles from the
primary. Now, this last figure seems to be wrong. According to my building
in Moray, they should orbit at about 16x10^6 miles so that day and night
areas are about the same size.
An area light for the sun is needed indeed. I used a glow (for latter
purposes), but I shall experiment further.
Larry Niven is not talking about a penumbra area in his books, as far as I
can tell. Night comes with the sun gradually cut-off by the shadow square.
Which doesn't exclude a penumbra of course.
Thomas
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"Bill Pragnell" <bil### [at] hotmailcom> schreef in bericht
news:web.435f7e721389c621731f01d10@news.povray.org...
>
> That's really good. I think it looks better than anything I managed. I
might
> have to dig out my code - we can have a Ring-off!
>
Thank you! And this is just a quick construction without any sophisticated
stuff!
> One point, however: to my mind, the shadowed areas of the arch should be
the
> same colour as the sky - just like the shadowed areas of the moon in our
> sky during daylight. The lit areas of the ring would probably not cast
that
> much light - certainly less than the earthlight cast onto the moon.
>
I agree. And Larry Niven imlies that the arch is invisible during daylight.
In my scene the arch is visible because there is no real atmospheric haze in
this scene, so the arch is viewed as if there were no atmosphere at all. The
blue sky here is faked. But this is the next step to solve indeed.
> Otherwise, keep 'em coming!
>
Hope to!
Thomas
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"Alain" <ele### [at] netscapenet> schreef in bericht
news:43603cc3$1@news.povray.org...
> >
> In the images I saw, the shadowing squares are between 1/2 and 2/3 of the
ring's radius. With such
> proportions, you have prety whide penumbraes.
>
What I forgot to say is that the Ringworld radius is 95x10^6 miles. This
means that the shadow squares are very close to the sun in comparison to the
Ringworld.
Remember the chapter about the shadow squares when Lying Bastard drifts
helplessly against the shadow square thread: it is very, very hot!
Thomas
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Wasn't it Thomas de Groot who wrote:
>
>Larry Niven is not talking about a penumbra area in his books, as far as I
>can tell. Night comes with the sun gradually cut-off by the shadow square.
That's exactly what a penumbra is. An observer standing in the penumbra
sees only part of the sun, the other part being cut off by the edge of
the shadow square. So the amount of light striking such an observer is
reduced.
--
Mike Williams
Gentleman of Leisure
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This is a much more dramatic image, I believe.
I used an area_light, the size of the sun; I placed the camera *near* one of
the rim walls; I reduced the camera angle to 75 degrees (earlier it was to
large).
Dimensions are almost meaningless on the Ringworld! In this scene, we are at
100 miles altitude, and still 10000 miles from the rim wall! Note however,
how the arch takes a more interesting shape in this view.
Thomas
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Attachments:
Download 'ringworld_04.jpg' (52 KB)
Preview of image 'ringworld_04.jpg'
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"Mike Williams" <nos### [at] econymdemoncouk> schreef in bericht
news:deR### [at] econymdemoncouk...
> Wasn't it Thomas de Groot who wrote:
> >
> >Larry Niven is not talking about a penumbra area in his books, as far as
I
> >can tell. Night comes with the sun gradually cut-off by the shadow
square.
>
> That's exactly what a penumbra is. An observer standing in the penumbra
> sees only part of the sun, the other part being cut off by the edge of
> the shadow square. So the amount of light striking such an observer is
> reduced.
>
Yes indeed, I stand corrected. Furthermore, Niven tells in fact how the
sunlight is reduced during the transition to night. My impression was
however, that it occurred pretty quickly.
Thomas
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"Thomas de Groot" <t.d### [at] internlnet> wrote:
> This is a much more dramatic image, I believe.
Very much so! Very nice.
> I used an area_light, the size of the sun; I placed the camera *near* one of
> the rim walls; I reduced the camera angle to 75 degrees (earlier it was to
> large).
I've been having problems with the rim walls. They are described as
mountains in the book; but I can't think of an easy way to implement them.
Sloping or curved walls are no problem, but texturing them is another
matter...!
How many shadow squares are you using? They look a bit different to mine...
Bill
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"Bill Pragnell" <bil### [at] hotmailcom> schreef in bericht
news:web.43609d6881b06728731f01d10@news.povray.org...
>
> How many shadow squares are you using? They look a bit different to
mine...
>
According to Niven, there are 20 shadow squares.
Thomas
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"Bill Pragnell" <bil### [at] hotmailcom> schreef in bericht
news:web.43609d6881b06728731f01d10@news.povray.org...
>
> I've been having problems with the rim walls. They are described as
> mountains in the book; but I can't think of an easy way to implement them.
> Sloping or curved walls are no problem, but texturing them is another
> matter...!
>
Yes, I have been pondering that issue too. I wonder if I shall not try to
make a mesh in Wings or Silo, so that individual areas can be textured
properly. Also, that would give the possibility to carve some mountains in
the rim wall, as well as the topography in the immediate neighbourhood of
the camera, let alone Fist-of-God!
Presently, I am experimenting with media inside a container to simulate the
atmosphere, but not yet really satisfying.
Thomas
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