[Radiance-general] Missing solar source visibility from gendaylit for multiple ambient-bounces

[Greg Ward]

Yes, the "-ps" option can affect the numerical results, as small, bright (or dark) regions might be missed with the default setting.

Cheers,
-Greg

> From: Germán Molina Larrain <germolinal at gmail.com>
> Subject: Re: [Radiance-general] Missing solar source visibility from gendaylit for multiple ambient-bounces
> Date: June 3, 2015 5:34:27 AM PDT
> 
> I have a question related to this.
> 
> Does the PS affect numerical results? or it is just a matter of "aesthetics" in the picture?
> 
> 2015-06-02 21:22 GMT-03:00 J. Alstan Jakubiec <alstan at jakubiec.net>:
> Hi Greg -- thanks for the reply. Indeed setting -ps 1 fixes the issue. At this resolution, the solar disc is actually ~5 x 5 pixels, so it must have been a very near miss with the default of -ps 4.
> 
> Best,
> Alstan
> 
> 
> On 6/2/2015 12:25 AM, Greg Ward wrote:
>> It's probably just being missed during the initial sampling, which is random.  Try setting "-ps 1" on the command line, or use "set ps 1" within rvu.
>> 
>> Cheers,
>> -Greg
>> 
>>> From: "J. Alstan Jakubiec" <alstan at jakubiec.net>
>>> Subject: Re: [Radiance-general] Missing solar source visibility from gendaylit for multiple ambient-bounces
>>> Date: June 1, 2015 6:53:24 AM PDT
>>> 
>>> To reply to my own post, I had another generic office model sitting around, so I applied the same materials, same sky model and same rendering parameters, but the solar disc showed up this time. So perhaps it had something to do with how obj2rad was constructing the surfaces? *Shrugs*
>>> 
>>> Alstan
>>> 
>>> On 6/1/2015 11:54 AM, J. Alstan Jakubiec wrote:
>>>> Dear List,
>>>> 
>>>> I'm running into a bit of a frustrating issue, and I am not sure what the cause might be. I am creating a sky model using gendaylit with a high amount of direct solar component as seen below,
>>>> > gendaylit 05 18 8.667 -W 881 63 -a 1 -o -104 -m -120
>>>> 
>>>> The issue is that when I render my scene using -ab 1, I can see the solar disc. When I render it with a higher number of ambient bounces, such as 4, the solar disc is absent from the final visualization. You can see the results here: 1 ambient bounce, 4 ambient bounces. You will notice that in the rendering with 4 ambient bounces, the shadows are still cast properly as if the sun is present.
>>>> I am using a slightly older version of Radiance right now (RADIANCE 4.2a lastmod  by  on w015t-001), but I suspect that isn't the root of the problem. This issue also occurs when I use gensky. I have never seen this kind of behavior before from Radiance. Does anyone have thoughts as to what might cause this? 
>>>> 
>>>> Thank you,
>>>> Alstan
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