POV-Ray : Newsgroups : povray.binaries.images : Ringworld (continued) Server Time: 14 Dec 2018 09:45:32 GMT
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From: Mike Horvath
Subject: Ringworld (continued)
Date: 6 Aug 2018 21:15:23
Message: <5b68ba6b@news.povray.org>
An old scene, but I've been sprucing it up in preparation toward 
uploading it to the Object Collection. I can't remember if it's to 
proper scale however. Also I'm thinking there may be a little too much 
cloud cover.


Mike


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From: Mike Horvath
Subject: Re: Ringworld (continued)
Date: 6 Aug 2018 21:34:46
Message: <5b68bef6$1@news.povray.org>
On 8/6/2018 5:15 PM, Mike Horvath wrote:
> An old scene, but I've been sprucing it up in preparation toward 
> uploading it to the Object Collection. I can't remember if it's to 
> proper scale however. Also I'm thinking there may be a little too much 
> cloud cover.
> 
> 
> Mike


Also, due to the sun being an area light, the unlit regions are much too 
small.


Mike


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From: Stephen
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 06:22:49
Message: <5b693ab9$1@news.povray.org>
On 06/08/2018 22:34, Mike Horvath wrote:
> On 8/6/2018 5:15 PM, Mike Horvath wrote:
>> An old scene, but I've been sprucing it up in preparation toward 
>> uploading it to the Object Collection. I can't remember if it's to 
>> proper scale however. Also I'm thinking there may be a little too much 
>> cloud cover.
>>
>>
>> Mike
> 
> 
> Also, due to the sun being an area light, the unlit regions are much too 
> small.
> 
> 

I got similar results when I tried it. I suspect Larry Niven got his 
maths wrong. I had to move the shadow plates closer to the Ringworld to 
get the day/night cycle equal.


-- 

Regards
     Stephen


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From: Thomas de Groot
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 06:42:33
Message: <5b693f59$1@news.povray.org>
On 7-8-2018 8:22, Stephen wrote:
> On 06/08/2018 22:34, Mike Horvath wrote:
>> On 8/6/2018 5:15 PM, Mike Horvath wrote:
>>> An old scene, but I've been sprucing it up in preparation toward 
>>> uploading it to the Object Collection. I can't remember if it's to 
>>> proper scale however. Also I'm thinking there may be a little too 
>>> much cloud cover.
>>>
>>>
>>> Mike
>>
>>
>> Also, due to the sun being an area light, the unlit regions are much 
>> too small.
>>
>>
> 
> I got similar results when I tried it. I suspect Larry Niven got his 
> maths wrong. I had to move the shadow plates closer to the Ringworld to 
> get the day/night cycle equal.
> 
> 

That, or scale down the area_light's effective surface. At this 
planetary scale the area effect would be hardly noticeable imo.

-- 
Thomas


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From: Stephen
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 08:20:07
Message: <5b695637$1@news.povray.org>
On 07/08/2018 07:42, Thomas de Groot wrote:
> On 7-8-2018 8:22, Stephen wrote:
>> On 06/08/2018 22:34, Mike Horvath wrote:
>>> On 8/6/2018 5:15 PM, Mike Horvath wrote:
>>>> An old scene, but I've been sprucing it up in preparation toward 
>>>> uploading it to the Object Collection. I can't remember if it's to 
>>>> proper scale however. Also I'm thinking there may be a little too 
>>>> much cloud cover.
>>>>
>>>>
>>>> Mike
>>>
>>>
>>> Also, due to the sun being an area light, the unlit regions are much 
>>> too small.
>>>
>>>
>>
>> I got similar results when I tried it. I suspect Larry Niven got his 
>> maths wrong. I had to move the shadow plates closer to the Ringworld 
>> to get the day/night cycle equal.
>>
>>
He is not the only one who got his maths wrong. Of course I meant closer 
to the star.

> 
> That, or scale down the area_light's effective surface. At this 
> planetary scale the area effect would be hardly noticeable imo.
> 

A point light gives the same result.

-- 

Regards
     Stephen


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From: Thomas de Groot
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 09:02:36
Message: <5b69602c$1@news.povray.org>
On 7-8-2018 10:20, Stephen wrote:
> On 07/08/2018 07:42, Thomas de Groot wrote:
>> On 7-8-2018 8:22, Stephen wrote:
>>> On 06/08/2018 22:34, Mike Horvath wrote:
>>>> On 8/6/2018 5:15 PM, Mike Horvath wrote:
>>>>> An old scene, but I've been sprucing it up in preparation toward 
>>>>> uploading it to the Object Collection. I can't remember if it's to 
>>>>> proper scale however. Also I'm thinking there may be a little too 
>>>>> much cloud cover.
>>>>>
>>>>>
>>>>> Mike
>>>>
>>>>
>>>> Also, due to the sun being an area light, the unlit regions are much 
>>>> too small.
>>>>
>>>>
>>>
>>> I got similar results when I tried it. I suspect Larry Niven got his 
>>> maths wrong. I had to move the shadow plates closer to the Ringworld 
>>> to get the day/night cycle equal.
>>>
>>>
> He is not the only one who got his maths wrong. Of course I meant closer 
> to the star.
> 
>>
>> That, or scale down the area_light's effective surface. At this 
>> planetary scale the area effect would be hardly noticeable imo.
>>
> 
> A point light gives the same result.
> 

Right. I would suggest then to test with a point light, following 
Stephen's maths, then try some area_light until it fits.

-- 
Thomas


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From: Stephen
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 10:29:48
Message: <5b69749c@news.povray.org>
On 07/08/2018 10:02, Thomas de Groot wrote:
> On 7-8-2018 10:20, Stephen wrote:
>> On 07/08/2018 07:42, Thomas de Groot wrote:
>>> On 7-8-2018 8:22, Stephen wrote:
>>>> On 06/08/2018 22:34, Mike Horvath wrote:
>>>>> On 8/6/2018 5:15 PM, Mike Horvath wrote:
>>>>>> An old scene, but I've been sprucing it up in preparation toward 
>>>>>> uploading it to the Object Collection. I can't remember if it's to 
>>>>>> proper scale however. Also I'm thinking there may be a little too 
>>>>>> much cloud cover.
>>>>>>
>>>>>>
>>>>>> Mike
>>>>>
>>>>>
>>>>> Also, due to the sun being an area light, the unlit regions are 
>>>>> much too small.
>>>>>
>>>>>
>>>>
>>>> I got similar results when I tried it. I suspect Larry Niven got his 
>>>> maths wrong. I had to move the shadow plates closer to the Ringworld 
>>>> to get the day/night cycle equal.
>>>>
>>>>
>> He is not the only one who got his maths wrong. Of course I meant 
>> closer to the star.
>>
>>>
>>> That, or scale down the area_light's effective surface. At this 
>>> planetary scale the area effect would be hardly noticeable imo.
>>>
>>
>> A point light gives the same result.
>>
> 
> Right. I would suggest then to test with a point light, following 
> Stephen's maths, then try some area_light until it fits.
> 

No, don't follow my maths.

Using the data from this site. I did a quick model.
http://www.alcyone.com/max/reference/scifi/ringworld.html
I adjusted the Shadow square ring radius until the day/night cycle 
looked equal.(multiplied the radius by 0.587587699)





-- 

Regards
     Stephen


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From: Stephen
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 10:33:04
Message: <5b697560$1@news.povray.org>
On 07/08/2018 11:29, Stephen wrote:
> No, don't follow my maths.
> 
> Using the data from this site. I did a quick model.
> http://www.alcyone.com/max/reference/scifi/ringworld.html
> I adjusted the Shadow square ring radius until the day/night cycle 
> looked equal.(multiplied the radius by 0.587587699)

A close up of the terminator on the Ringworld.
The area light does make a difference.
Using
  light_source {  // Light_Source2
   < 0.000000, 0.000000, 0.000000 >, colour rgb <1.000,1.000,1.000>*1.500
   area_light <3.400000,0.000000,0.000000>, 
<0.000000,3.400000,0.000000>, 23, 23

   circular
   orient
   adaptive 5

-- 

Regards
     Stephen


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From: clipka
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 10:51:15
Message: <5b6979a3$1@news.povray.org>
Am 07.08.2018 um 12:33 schrieb Stephen:

> A close up of the terminator on the Ringworld.
> The area light does make a difference.
> Using
>  light_source {  // Light_Source2
>   < 0.000000, 0.000000, 0.000000 >, colour rgb <1.000,1.000,1.000>*1.500
>   area_light <3.400000,0.000000,0.000000>, <0.000000,3.400000,0.000000>,
> 23, 23
> 
>   circular
>   orient
>   adaptive 5

And it better does. You don't want the light to blink off
instantaneously - you do want some twilight time.


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From: Thomas de Groot
Subject: Re: Ringworld (continued)
Date: 7 Aug 2018 11:07:49
Message: <5b697d85$1@news.povray.org>
On 7-8-2018 12:51, clipka wrote:
> Am 07.08.2018 um 12:33 schrieb Stephen:
> 
>> A close up of the terminator on the Ringworld.
>> The area light does make a difference.
>> Using
>>   light_source {  // Light_Source2
>>    < 0.000000, 0.000000, 0.000000 >, colour rgb <1.000,1.000,1.000>*1.500
>>    area_light <3.400000,0.000000,0.000000>, <0.000000,3.400000,0.000000>,
>> 23, 23
>>
>>    circular
>>    orient
>>    adaptive 5
> 
> And it better does. You don't want the light to blink off
> instantaneously - you do want some twilight time.
> 

I agree. What I meant earlier was that, with the camera at /planetary/ 
distances from the ring, the penumbra would hardly be visible. Up close, 
and more so on the ring surface, of course the penumbra matters. 
However, if the area_light is set while the camera is at a /planetary/ 
distance, it will most probably be grossly exaggerated because otherwise 
you would not be able to see it properly in a render.

-- 
Thomas


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