POV-Ray : Newsgroups : povray.advanced-users : HDR and brightness : Re: HDR and brightness Server Time
23 Jun 2024 14:52:34 EDT (-0400)
  Re: HDR and brightness  
From: clipka
Date: 23 Feb 2018 13:30:30
Message: <5a905dc6$1@news.povray.org>
Am 23.02.2018 um 00:51 schrieb Mike Horvath:
> Can I achieve the same brightness using an HDRI sky as using a light
> source? Or are there limits on how bright a scene can be?

Technically, that depends on the HDRI file format used.

In POV-Ray, light source brightness is stored internally using so-called
"single precision" floating point values; these can range as high as ca.
3.4*10^38.

The Radiance HDR file format uses a proprietary floating point-ish
format with values ranging as high as ca. 1.7*10^38, so not much
difference there.

OpenEXR files are usually stored using "half precision" floating point
values; these can range no higher than 65504 (ca. 6*10^4). However,
OpenEXR can also use "single precision" floating point values as an
alternative. (It even allows for the use of "double precision" floating
point values, which can range as high as ca. 1.8*10^308, but POV-Ray
would limit them internally to single precision.)


In practice, I don't expect the limitations of standard (half precision)
OpenEXR to be of any significance except in fringe cases, such as trying
to model a very bright point-like light source.


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