On 07/08/2018 12:07, Thomas de Groot wrote:
> 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.
> 

Do you mean that the penumbra would need to be exaggerated so it can be 
seen?
I thought that too but when I created two big sticks located at opposite 
sides of the star and clipping the same edge of a shadow square. The 
divergence at the ring was quite large.
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.
This image was taken from slightly beyond the other side of the ring and 
above a bit.


-- 

Regards
     Stephen

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