[Radiance-general] incident ray angles

Fri Feb 21 04:54:03 PST 2014

Hello Jia,

The DAYSIMps addon to Daysim by Penn State, "Considers photosensor spatial  
sensitivity, location, aiming, control algorithm, and calibration." You  
can see on page 11 it works by using some '.sen' files that describe the  
sensor sensitivity, and there is a new sim_photosensor program in the  
Daysim toolchain to enable this. The 2013 workshop presentation by Richard  
Mistrick is probably of use.

Best,
Alstan

On Fri, 21 Feb 2014 04:12:35 -0500, Greg Ward <gregoryjward at gmail.com>  
wrote:

> Hi Jia,
>
> I put my answers inline, and included your second e-mail at the bottom...
>
>>
>> From: Jia Hu <hujia06 at gmail.com>
>>
>> Date: February 20, 2014 7:37:42 PM GMT+01:00
>>
>>
>>>> Hi Greg and David,
>>
>> That is great.  I looked at the man page of rsensor program, that is  
>> what I need.  I have a few questions for which I am struggling.
>> you mentioned I still have to use a cone to cutoff light even if I  
>> define the sensitivity data files?  should I list all from 0-90 (row  
>> >>degree) in the row or just view angle range (e.g., from 0 - 54 deg in  
>> row)?   does the program do some interpolation for angles are >>not  
>> defined in the sensor files?
> The cone is an easy (but computationally wasteful) alternative to using  
> rsensor if all you need is a cut-off.  There is no reason to use such a  
> device >with rsensor.
>
>> Our program was built based on Daysim, and use gen_dc to generate  
>> daylight coefficient and us ds_illum to calculate the sensor  
>> >>readings. The readings are cosine weighted, but it seems no way to  
>> integrate rsensor with ds_ill or .dc files. I understand the 3 or >>5  
>> phase DC methods is good to handle this. Since we already have the code  
>> from Daysim, it may be easy to directly integrate >>resensor with  
>> current Daysim generated .dc files? Do you have some suggestion?
> I will leave this to the Daysim experts to answer.  Using rsensor with  
> the 3-phase method is more likely to succeed as you point out.
>
>> If we use three phase DC method, we have to generate the BSDF files,   
>> genBSDF +f +b will double the time, so for blinds in the >>south wall  
>> settings, I only need use deault (+b only, not +f), is tha right?  +b  
>> will generate Transmission From (Window 6 >>convention), is that right?
> Yes, that's correct.
>
>>  Thank you very much,
>>
>> Jia
>
> Regarding your second question, the 10000 sensor samples are integrated  
> to a single value, and this is the way it works.  You can of course  
> change >this with the rsensor -rd option, but your accuracy will  
> suffer.  In the scheme of things, 10000 rays is not too big a number of  
> samples if your scene >has a lot going on.  Convergence of Monte Carlo  
> approaches generally proceeds as 1/sqrt(N) for N samples.
>
> Best,
> -Greg
>
>>
>> On Thu, Feb 20, 2014 at 4:29 AM, Greg Ward <gregoryjward at gmail.com>  
>> wrote:
>>> Have you investigated the program "rsensor"?  It should be able to  
>>> handle any distribution you like.
>>>
>>> By default, the -I option of rtrace gives you a cosine-weighted  
>>> irradiance value.  If you need to add a cut-off, you can compute -I in  
>>> >>>the apex of a black cone of the appropriate size.
>>>
>>> -Greg
>>>
>>>>
>>>> From: Jia Hu <hujia06 at gmail.com>
>>>>
>>>> Date: February 20, 2014 8:45:33 AM GMT+01:00
>>>>
>>>>
>>>>>>>> Hello,
>>>>
>>>> I have a sensor and the sensor has different readings according to  
>>>> angle between incident ray and normal. Theoretically, >>>>this  
>>>> readings should be [cos(theta)*value of incident rays] hitting the  
>>>> sensor point (theta = angle between ray hitting the >>>>surface and  
>>>> sensor normal).  However,t our sensor is not this  relationship and I  
>>>> have to adjust the simualtion results to fit >>>>the actual sensor  
>>>> readings.
>>>>
>>>> one of the methods I can think of is to get directions of all the  
>>>> incident rays hitting the sensor point and then >>>>calculate all the  
>>>> angles between incident rays and sensor normal, and adjust the  
>>>> radiance values before using rtrac to >>>>calculate the actual  
>>>> illuminance values.  Is that feasible?   I notice there is a "t"  
>>>> option in rtrace, but it will return all >>>>the rays, not just rays  
>>>> hitting the sensor points.Radiance traces only 1 ray from the sensor  
>>>> points or sample a number of rays from sensor point? (my understaning  
>>>> >>>>was that rtrace first traces a number of rays to check DIRECT  
>>>> light source and get the results, and then traces a >>>>SINGLE ray  
>>>> following the sensor normal and then sampling more when hitting a  
>>>> surface? if in this case, how can I >>>>determine the anges of direct  
>>>> and indirect rays?)
>>>> Thanks,
>>>>
>>>> jia
>>
>
> +++++++++++++
>>
>> From: Jia Hu <hujia06 at gmail.com>
>>
>> Date: February 21, 2014 6:43:10 AM GMT+01:00
>>
>>
>>>> Hello,
>>
>>>> There are 30 sensors in the space, each of which has sensor spatial  
>>>> response file and use rsensor to calculate illuminance >>values.  If  
>>>> I use three phase method to conduct annual simulation. My current  
>>>> method is to use:  rsensor -h -vf view.vf . to >>generate the 10000  
>>>> rays and use these rays to calcualte V matrix.  in other words, I am  
>>>> using three phase method to calculate >>10000 sensor points. At the  
>>>> end, only a single sensor values are calculated.   Is there any  
>>>> better way?
>>
>>>> Thanks!
>>
>>>> Jia
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