[Radiance-general] Mkillum bsdf + sample density

[Andrew McNeil]

Hi Greg,

Thanks for your response, that d= option behavior makes sense now, but leads
to a question about the number of output directions in illum.dat...

My BSDF has 18 "latitudes"  and 24 "azimuths"  (432 divisions)
The resulting illum.dat is 13x39 = 507 angles

After considering your response, I guess the difference between 432 and 507
is a result of a BSDF pattern that doesn't match the typical radiance
hemisphere division scheme used by mkillum?

I'm guessing that mkillum gets from 432 to 507 by:
sqrt(432/pi) = 12
12*pi = 38
12+1 x 38+1  =  13 x 39  = 507
Am I close?  I don't have an explanation for adding one to each dimension.

Finally, the sampling pattern of my BSDF (18x24) and the hemisphere division
used by mkillum (13x39) results in double-sampling of some BSDF angles and
non-sampling of others.  In conclusion I would be best served by using the
typical radiance hemisphere division ( m x pi*m ) to generate a BSDF that
"agrees" with mkillum.  (or should I stop speculating...)

Andy
 



On 12/10/09 2:55 PM, "Greg Ward" <gregoryjward at gmail.com> wrote:

> Hi Andy,
> 
> The mkillum sample density is set by the resolution of the BSDF, since
> there's not much point in using more (or fewer) samples than the
> transmission data allows.
> 
> -Greg
> 
>> From: Andrew McNeil <andrew.mcneil at arup.com>
>> Date: December 10, 2009 12:42:43 PM PST
>> 
>> Hi Everyone / Greg,
>> 
>> Is there a way to specify both the sample density and a bsdf for
>> mkillum?
>> For example in the file I feed to mkillum I have:
>> #@mkillum d=128 d=bsdf.xml
>> 
>> The second Œd¹ seemingly reverts the sample density the default
>> (32).  If I do it the other way I think it omits the bsdf data.  Am
>> I missing a trick?
>> 
>> Best,
>> Andy
> 
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