[Radiance-general] BSDF xml into Radiance

[Guglielmetti, Robert]

Yeah, this is a nice feature that obviates the need for oversampling to
reduce image noise in many cases. This feature is in the NREL packages,
BTW.

- Rob



On 7/25/12 4:10 PM, "Daniel C. Glaser" <daniel at lightfoundryllc.com> wrote:

>Dear Greg,
>   Thank you for letting us know about the -c option.  I am going to try
>it with rtcontrib (sensors) and wanted to ask for advice on how to setup
>the points for averaging.  For example, if I choose 4 for -c, do I send
>in the same point 4 times or is there a heuristic for perturbing or
>regularly spacing these points for improving results?
>   Thanks for creating this feature!
>
>- Dan
>
>On 7/25/2012 10:44 AM, Greg Ward wrote:
>> Hi Lars,
>>
>> Andy probably is the right person to respond to this, but as he's on a
>>vacation until the end of the month, I thought I'd offer a couple of
>>comments (inline).
>>
>> Cheers,
>> -Greg
>>
>>> From: "Lars O. Grobe" <grobe at gmx.net>
>>> Date: July 25, 2012 1:18:42 AM PDT
>>>
>>> Hi Andy, hi list-subscribers,
>>>
>>> I just came across this recent message about the usability of the bsdf
>>> material type with patch-based models of the sky including direct sun
>>> and complex fenestration. To avoid misunderstandings, I will try a
>>>short
>>> summary for others to comment on available options for annual
>>> simulations with complex glazing:
>>>
>>>
>>> 1) classic radiance tools (rpict, rtrace), complemented by mkillum to
>>> relax ambient setting.
>>>
>>> Advantages: low noise, validated.
>>>
>>> Disadvantages: very slow for annual simulations, no support when
>>> non-planar specular reflective surfaces are involved.
>> More specifically, non-planar, specular reflectors run into trouble for
>>insolation.  Cloudy skies or sunless skies are no problem.
>>
>>> 2) rtcontrib and patch-based model.
>>>
>>> Advantages: faster for annual simulations.
>>>
>>> Disadvantages: noise, nice images require high (slow) -ad and cannot be
>>> optimized using mkillum, limitations about specular non-planar
>>> reflectors apply.
>> The accuracy of non-planar, specular reflectors is actually better than
>>#1, but the results are somewhat noisy.  A new -c option to vwrays
>>(coupled with the rtcontrib -c option) is a good way to reduce noise
>>that is available in the latest HEAD.  This is a better way to reduce
>>noise than increasing -ad, and less costly.
>>
>>> 3) rtcontrib and patch-based model, bsdf.
>>>
>>> Advantages: support for non-planar reflectors, should be slightly
>>>faster
>>> than 2) as the fenestration system does not have to be traced
>>>internally
>>> - did anyone compare?
>>>
>>> Disadvantages: still high -ad settings required leading to extended
>>> rendering times and still no way to get mkillum in, tends to
>>> underestimate direct sun (according Andy's message).
>>>
>>>
>>> 4) three-phase-method.
>>>
>>> Advantages: very fast, can also be used with non-planar specular
>>> reflectors as bsdf data is supported.
>>>
>>> Disadvantages: requires quite a lot of set-up work, e.g. subdivisions
>>>to
>>> reflect external obstructions. Patches visible in the results,
>>> fenestration geometry is not visible.
>> Andy has proposed an improved annual simulation method, which we hope
>>to work on next year, to remedy the direct solar sampling difficulties
>>in the 3-phase method.  It should also alleviate problems with external
>>facade geometry and reduce the need to subdivide windows.
>>
>>> 5) pmap.
>>>
>>> Advantages: can be used with non-planar reflectors and multi-peak
>>> transmission.
>>>
>>> Disadvantages: unknown status (any news?), not integrated with
>>>rtcontrib
>>> (contributions would need to be rendered manually).
>>>
>>>
>>> So if I need a way to generate images with visible fenestration
>>> geometry, the only reliable option would be 2), which requires very
>>> hight settings for -ad and thud will still be rather time-consuming, if
>>> noise is to be controlled.
>>>
>>> Cheers, Lars.
>>>
>>> On Tue, 2012-06-12 at 08:43 -0700, Andrew McNeil wrote:
>>>
>>>> Though I've found that the BSDF material doesn't work well for
>>>> daylight coefficient based annual simulations (I'm assuming dds.bash
>>>> is a dynamic daylight simulation script).  Putting the solar radiance
>>>> into skypatches relies on probabilistic sampling to find patches
>>>> containing the sun, and if you don't have much direct transmission
>>>> from the direction of the sun, you aren't likely to find the sun.  Not
>>>> finding the sun causes big errors.
>> _______________________________________________
>> Radiance-general mailing list
>> Radiance-general at radiance-online.org
>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>
>>
>
>
>
>_______________________________________________
>Radiance-general mailing list
>Radiance-general at radiance-online.org
>http://www.radiance-online.org/mailman/listinfo/radiance-general