[Radiance-general] Uniform sky

[Vera Liu]

Thank you all for the replies! I got it working now. I can see that -ab set
to zero indicates no indirect calculation so I think this should give me
the ground truth values. Thank you all very much.

Best,
Vera


On Mon, May 5, 2014 at 7:02 AM, Thomas Bleicher <tbleicher at gmail.com> wrote:

> Vera
>
> This sounds like you are trying to create something like an "ambient
> occlusion" or "clay rendering"; the closer you are to an object the more
> obstructed the view of the sky is and so the ground gets darker.
>
> You can indeed create this using a uniform sky but you have to use "-ab 1"
> for your rendering or the sky will not contribute to the scene. The "no
> light sources found" warning comes up because a "glow" material that is
> used for the sky technically does not count as a light "source" Radiance.
>
> If you plan to use the rendering for analysis you can set the sky
> brightness to a known quantity so that the rendering can be interpreted as
> an absolute value of the obstruction of the sky. I think John Mardaljevic
> wrote down the math for this in the Rendering with Radiance chapter on
> skies/daylight. You should also add "-av 0 0 0" or the added ambient value
> will skew your results.
>
> Regards,
> Thomas
>
>
>
>
> On Sun, May 4, 2014 at 9:50 PM, Vera Liu <lizzielyh at gmail.com> wrote:
>
>> Hi Joe,
>> For the ground truth I'm thinking about just the surface lit by the light
>> at each pixel without any ray tracing. Basically, the RGB of the surface as
>> it would be if it were directly lit by the light without any
>> interreflections or specularities. I figured that a uniform sky would do
>> the trick.
>>
>> Best,
>> Vera
>>
>>
>> On Sun, May 4, 2014 at 7:08 PM, Joe Smith <the.oat.cracker at gmail.com>wrote:
>>
>>> Hi, Vera, may I ask what you mean by "ground truth pixel value"?
>>>
>>> - JS
>>>
>>> Vera Liu <lizzielyh at gmail.com>于2014年5月5日星期一写道：
>>>
>>> Hi Radiance experts,
>>>> I want to get the ground truth pixel values of a scene generated by
>>>> radiance and I figured the best way is to use a uniform sky where the sky
>>>> it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
>>>> !gensky 4 1 12 +s -a 40 -o 98 -m 105
>>>> skyfunc glow sky_glow
>>>> 0
>>>> 0
>>>> 4 1 1 1 0
>>>> sky_glow source sky
>>>> 0
>>>> 0
>>>> 4 0 0 1 180
>>>>
>>>> This results in shadows in the final scene. I found that -u option or
>>>> -c option can give me a uniform cloudy sky and maybe give me the ground
>>>> truth values. I tried both of them but always get 'no lighting source
>>>> warning' and a very dark scene when I try to use rpict and pfilt on the
>>>> .oct generated. I think I might be understanding something wrong. Could you
>>>> please give me a hint on this? The two options I tried are:
>>>> !gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
>>>> and
>>>> !gensky -ang 45 0 -c -b 1
>>>>
>>>> Thank you very much!
>>>> Best,
>>>> Vera
>>>>
>>>
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