[Radiance-general] A modern comparison of Radiance and other rendering engines

[Germán Molina Larrain]

Hello,

I agree with Lars in everything, but I also want to add some things:

   1. I believe that, for scientific use of daylight simulations, you need
   extensive numerical validation. Some renders are not focused on that, but
   only on speed and generating "photorealistic images", which are different
   from "photometrically correct images"... Does that make sense? I think this
   is the most important difference between Radiance and other renderers out
   there.
   2. In 2012 I asked this in the PBRT google group, and they advice me to
   keep using Radiance (LINK
   <https://groups.google.com/forum/#!topic/pbrt/xQlfQnPYPB0>)
   3. The irradiance Cache seem to be pretty unique for Radiance.... ?

Best,

Germán



2018-01-29 9:23 GMT-03:00 Lars O. Grobe <grobe at gmx.net>:

> Hi,
>
> there are even more renderers, e.g. pbrt/luxrender, mitsuba, ....
>
> I think the main difference is - that the difference is not known. In the
> Radiance universe, a lot of work is spent on testing the validity of the
> models and methods. This allows professionals to rely on the software, as
> long as they are within the boundaries of the validations. There is a lot
> of other software capable to solve the global illumination, but few people
> will rely on it for quantitative studies before they have been validated.
>
> Another, really important reason that people stick with Radiance
> regardless what exists "out there" is that for daylight simulation, a good
> renderer does not help you without the ecosystem of tools making it a
> useful simulation environment. So to make use of climate data, perform
> annual simulations, model the often exotic properties of fenestration, and
> analyze the results, you need more than the ray-tracer.
>
> Finally, what may appear as an advantage - the quick introduction of new
> features and state-of-the-art rendering algorithms, can become a serious
> drawback. The "modular" renderers out there, e.g. Mitsuba, allow to combine
> different modules. Other, often commcercial renderers, may bring new
> features with every release (and may not even tell you if something
> changed). However, if you need to redo all your validations with every
> combination of such modules, or any change in your implementation, you
> hardly reach the point where you can make use of the software.
>
> So while there exist lots of codes to trace light, the motivation of the
> developers usually is not to ensure valid quantitative simulation for
> building performance analysis. In fact, most software in this field is
> based on tuning and adapting good-old radiosity.
>
> https://www.janwalter.org/RadianceVsYouNameIt/radiance_vs_younameit.html
>
> This is an impressive coverage of rendering engines! It just lacks the
> numbers. So while images may look similar, we do not know about
> quantitative agreement.
>
> Cheers,
> Lars
>
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