On 08/08/2018 07:22, Thomas de Groot wrote:
> On 7-8-2018 14:01, Stephen wrote:
>> On 07/08/2018 12:23, Stephen wrote:
>>> I might try moving the shadow square radius back to the quoted radius 
>>> and adjust the length of the shadow square to get equal day/night.
>>
>> As threatened. :-)
>>
>> Twilight is less obvious.
>>
> 
> Yes, but I think it is looking natural from that distance. On the ring, 
> twilight would be gradual, as expected.
> 

I think so too. The image I posted yesterday at 22:52, my time. Does 
show the gradual darkening. The render did take an hour and a half to 
complete.

-- 

Regards
     Stephen

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On 07/08/2018 23:39, Mike Horvath wrote:
> On 8/7/2018 5:52 PM, Stephen wrote:
>> Funnily enough, I did not notice that when I read the books. ;)
>> It is PovRay's fault. It is too realistic. :)
>>
>> I think it is better to bring the shadow shields nearer the sun, for 
>> the data I found.
>>
>> This last image (I promise) using Alain's settings, has a stary 
>> background to show that the night part of the ring is occluding the 
>> stars.
>>
>> BTW Thanks for starting the thread. It has been a distraction for me 
>> when I don't feel up to starting a new project.
>>
>>
> 
> Hold on. I just noticed I wasn't using the correct sizes for the shadow 
> squares. And I had 40 of them instead of 20. I will need to redo them.
> 
> 

:)
The way of the world. :)


-- 

Regards
     Stephen

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On 8-8-2018 9:34, Stephen wrote:
> On 08/08/2018 07:22, Thomas de Groot wrote:
>> On 7-8-2018 14:01, Stephen wrote:
>>> On 07/08/2018 12:23, Stephen wrote:
>>>> I might try moving the shadow square radius back to the quoted 
>>>> radius and adjust the length of the shadow square to get equal 
>>>> day/night.
>>>
>>> As threatened. :-)
>>>
>>> Twilight is less obvious.
>>>
>>
>> Yes, but I think it is looking natural from that distance. On the 
>> ring, twilight would be gradual, as expected.
>>
> 
> I think so too. The image I posted yesterday at 22:52, my time. Does 
> show the gradual darkening. The render did take an hour and a half to 
> complete.
> 

I often need to take stock again and again of the gigantic distances and 
sizes we are dealing with in a planetary system. It is something quite 
difficult to grasp, and rendering things like the Ringworld makes us 
forget them, reducing them to simple rings to be taken into our hands ;-)

-- 
Thomas

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Okay, I uploaded my scene to here:

http://lib.povray.org/searchcollection/index2.php?objectName=Ringworld&version=2.0&contributorTag=SharkD

I also attached my latest render to this post. The shadow squares' 
widths now match what was apparently stated in the books. The shadowed 
regions on the ring look much better now.

However, I had to double the height of the shadow squares in order to 
block out the sun. See the parameter `RWorld_Shadow_Square_Width`. I'm 
not sure why this was necessary, as the original height was equal to the 
sun's diameter, and should have fully blocked its light.

Oh well.


Mike

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Attachments:
Download 'ringworld_foggy_save_03.png' (99 KB)

Preview of image 'ringworld_foggy_save_03.png'

On 08/08/2018 15:08, Mike Horvath wrote:
> Okay, I uploaded my scene to here:
> 
>
http://lib.povray.org/searchcollection/index2.php?objectName=Ringworld&version=2.0&contributorTag=SharkD

> 
> 
> I also attached my latest render to this post. The shadow squares' 
> widths now match what was apparently stated in the books. The shadowed 
> regions on the ring look much better now.
> 
> However, I had to double the height of the shadow squares in order to 
> block out the sun. See the parameter `RWorld_Shadow_Square_Width`. I'm 
> not sure why this was necessary, as the original height was equal to the 
> sun's diameter, and should have fully blocked its light.
> 

Do the two area_light vectors <Axis_1> and <Axis_2> extend beyond the 
star's volume?

> Oh well.
> 
> 

I like the image especially the shadows cast by the shadow squares in 
the solar wind. :)

Unfortunately I don't have CIE.inc or lightsys.inc installed. :(


-- 

Regards
     Stephen

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Mike Horvath <mik### [at] gmailcom> wrote:
> I also attached my latest render to this post. The shadow squares'
> widths now match what was apparently stated in the books. The shadowed
> regions on the ring look much better now.
>
> However, I had to double the height of the shadow squares in order to
> block out the sun. See the parameter `RWorld_Shadow_Square_Width`. I'm
> not sure why this was necessary, as the original height was equal to the
> sun's diameter, and should have fully blocked its light.

Yay for more Ringworld! Nice image.

I don't remember any of the details any more, but I remember spending time going
through the book for measurements and descriptions when I last tried this (some
years ago now), and I don't recall any issues like you describe. Someone
mentioned ambient in the foregoing discussion - of course, the lit areas of the
Ring would cast secondary light onto the night areas. I'm sure Niven mentioned
arch-light in place of moonlight somewhere...

And of course his maths was bad - he had to write an entire sequel novel just to
deal with the Ringworld's intrinsic instability ;-)

Bill

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On 08/08/2018 20:31, Bill Pragnell wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> I also attached my latest render to this post. The shadow squares'
>> widths now match what was apparently stated in the books. The shadowed
>> regions on the ring look much better now.
>>
>> However, I had to double the height of the shadow squares in order to
>> block out the sun. See the parameter `RWorld_Shadow_Square_Width`. I'm
>> not sure why this was necessary, as the original height was equal to the
>> sun's diameter, and should have fully blocked its light.
> 
> Yay for more Ringworld! Nice image.
> 
> I don't remember any of the details any more, 

There is a link on this site. ;)
http://www.infradead.org/~wmp/proj_rings.html


> but I remember spending time going
> through the book for measurements and descriptions when I last tried this (some
> years ago now), and I don't recall any issues like you describe. Someone
> mentioned ambient in the foregoing discussion - of course, the lit areas of the
> Ring would cast secondary light onto the night areas. I'm sure Niven mentioned
> arch-light in place of moonlight somewhere...
> 

He did, I had forgotten.



-- 

Regards
     Stephen

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On 8/8/2018 3:31 PM, Bill Pragnell wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> I also attached my latest render to this post. The shadow squares'
>> widths now match what was apparently stated in the books. The shadowed
>> regions on the ring look much better now.
>>
>> However, I had to double the height of the shadow squares in order to
>> block out the sun. See the parameter `RWorld_Shadow_Square_Width`. I'm
>> not sure why this was necessary, as the original height was equal to the
>> sun's diameter, and should have fully blocked its light.
> 
> Yay for more Ringworld! Nice image.
> 

Thanks!

> I don't remember any of the details any more, but I remember spending time going
> through the book for measurements and descriptions when I last tried this (some
> years ago now), and I don't recall any issues like you describe. Someone
> mentioned ambient in the foregoing discussion - of course, the lit areas of the
> Ring would cast secondary light onto the night areas. I'm sure Niven mentioned
> arch-light in place of moonlight somewhere...
> 
> And of course his maths was bad - he had to write an entire sequel novel just to
> deal with the Ringworld's intrinsic instability ;-)
> 
> Bill
> 

I am using the stats from Niven's website:

http://news.larryniven.net/concordance/content.asp?page=Ringworld%20Appendix#Params


Mike

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On 8/8/2018 1:05 PM, Stephen wrote:
> On 08/08/2018 15:08, Mike Horvath wrote:
>> Okay, I uploaded my scene to here:
>>
>>
http://lib.povray.org/searchcollection/index2.php?objectName=Ringworld&version=2.0&contributorTag=SharkD

>>
>>
>> I also attached my latest render to this post. The shadow squares' 
>> widths now match what was apparently stated in the books. The shadowed 
>> regions on the ring look much better now.
>>
>> However, I had to double the height of the shadow squares in order to 
>> block out the sun. See the parameter `RWorld_Shadow_Square_Width`. I'm 
>> not sure why this was necessary, as the original height was equal to 
>> the sun's diameter, and should have fully blocked its light.
>>
> 
> Do the two area_light vectors <Axis_1> and <Axis_2> extend beyond the 
> star's volume?
> 

1. the axis lengths are equal to the sun's diameter
2. the area light is circular and oriented
3. the sun's diameter should be equal to the shadow squares' height 
according to Niven's website
4. an array of point lights in the shape of a sphere does not suffer 
from the issues I'm experiencing


>> Oh well.
>>
>>
> 
> I like the image especially the shadows cast by the shadow squares in 
> the solar wind. :)
> 

Thanks!


> Unfortunately I don't have CIE.inc or lightsys.inc installed. :(
> 
> 

I use them in nearly everything. Not sure why. Probably just habit.


Mike

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Le 18-08-07 à 11:20, Stephen a écrit :

> Thanks Alain, I seldom use area lights and this is the first time I have 
> used adaptive.
> When you said samples is that what the offline help names Size_1 & 
> Size_2, in the line;
> AXIS_1_VECTOR, AXIS_2_VECTOR, Size_1, Size_2?
> 

Yes, Size_1 and Size_2.

AXIS_1_VECTOR and AXIS_2_VECTOR set the extent of the area_light.
Size_1 and Size_2 set the number of components, or samples, in the 
area_light.

When using orient, the pairs need to be of the same size. The 
AXIS_n_VECTORs need to have the same length and be perpendicular.
And, you need Size_1 = Size_2.

When using adaptive, always start with adaptive 0 and only increase if 
you really need to.



Alain

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