[Radiance-general] BSDF xml into Radiance

[Daniel C. Glaser]

Hi Greg,
   For a preliminary trial, I passed in the same point 4 and 16 times 
and saw the smoothing.  Thank you for incorporating this directly into 
these utilities!

- Dan


On 7/25/2012 4:21 PM, Gregory J. Ward wrote:
> Hi Dan,
>
> If you want your sensors averaged over some small area (rather than measured at a point), then you can jitter the sample location.  Otherwise, just repeat the point value N times corresponding to your -c argument.
>
> -Greg
>
>> From: "Daniel C. Glaser" <daniel at lightfoundryllc.com>
>> Date: July 25, 2012 3:10:36 PM PDT
>>
>> 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.
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>>>
>>>
>>
>>
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