[Radiance-general] DGP studies: image size

[Jan Wienold]

Hi Randolph,

as the question is general, the clear answer is no - this cannot be 
recommended in general. Just imagine having a 180 degree fish eye 
resolving the sun (or reflection of it)  with 0.5 degree and having only 
500x500 pixels. We made this recommendation of 800x800 10 years ago, 
when a) evalglare was in its first version (in the meanwhile I optimized 
the code which results in average to 30% time saving compared to the 
first versions) b) computer power was less. Nowadays I recommend 
1000x1000, especially when dealing with fabrics/translucent materials 
with a certain peak transmission.
Another example: Imagine you want to do a electric lighting analysis 
with small emitting surfaces (e.g. bunch of single LEDs) of high 
luminances. In that case you really want to resolve the glare sources 
not only with 1 pixel each.

But on the other hand, there are also many cases, where you are totally 
fine with 500x500, when your potential glare sources are rather large.

I'm currently performing a study including images from several groups - 
we are having more than 1000 images and I would say in average an 
evalglare run was about 7s per image (using 1000x1000). The more glare 
sources are found in the image, the longer it takes (this has to do with 
the combining the "glare source pixel" to glare sources). So for a scene 
with a large amount of glare sources you might end up with 3-4min per 
image.

Jan



On 08/03/16 03:19, Randolph M. Fritz wrote:
> The original paper recommends 800x800 images for glare studies. Anyone 
> have a feeling for how hard and fast that is? Would the canonical 
> 500x500 be enough?
>
> -- 
> Randolph M. Fritz, Lighting Design and Simulation
> +1 206 659-8617 || rmfritz3 at gmail.com <mailto:rmfritz3 at gmail.com>
>
>
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-- 
Dr.-Ing.  Jan Wienold
Ecole Polytechnique Fédérale de Lausanne (EPFL)
EPFL ENAC IA LIPID

http://people.epfl.ch/jan.wienold
LE 1 111 (Office)
Phone    +41 21 69 30849

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