Going off off-topic, I think an example of this should be in the Pov-Ray  
insert-menu with a RSOCP scene.

On Mon, 22 Jun 2015 18:07:16 +0200, clipka <ano### [at] anonymousorg> wrote:

> Am 21.06.2015 um 09:44 schrieb Nekar Xenos:
>> Can some explain to me what exactly PBR is. In Pov-Ray terms would be
>> nice :)
>
> PBR avoids old-school shading models and rendering algorithms that were  
> designed to achieve a particular effect, and instead uses mechanisms  
> that were designed to model the underlying physical processes.
>
> POV-Ray has been heavily geared towards PBR in recent times, and UberPOV  
> should by now be a viable PBR tool, provided you stick to the following  
> rules:
>
> - Don't use "ambient". Use radiosity instead, and "emission" where  
> applicable.
>
> - Don't use "phong" or "specular". Rely on reflections instead (which,  
> for good results, mandates that you use blurred reflections).
>
> - If you decide that you do need to use "phong" or "specular", prefer  
> "specular", and /always/ use it in tandem with reflection, making sure  
> that the parameters match: Use "specular albedo N" where N is the  
> maximum reflection intensity, and use "fresnel on" or "metallic on" for  
> the entire finish block just as you do in the reflection block. Also,  
> make sure to specify the same "roughness" in the reflection block.  
> (You'll need an up-to-date version of UberPOV for "fresnel on" in the  
> entire finish block and "roughness" in the reflection block.)
>
> - Always use "fresnel on" for reflections (don't forget to specify  
> "ior"), or "metallic on" where applicable, and always use 0.0 for the  
> minimum reflection (or leave it out, specifying the maximum reflection  
> only).
>
> - Don't use colours as reflection parameters. Use the "metallic"  
> mechanism for this instead.
>
> - Don't use "light_source". Use objects with "emission" (or a sky  
> sphere) and radiosity instead.
>
> - If you decide that you do need to use "light_source", always use a  
> well-matching "looks_like" object with "no_radiosity on", always use  
> "area_light", always use "fade_power 2" with "fade_distance" set to  
> (roughly) half the area light vectors' dimensions, and always use  
> "area_illumination" unless the light source is sufficiently far away.  
> Also, do make use of photon mapping.
>
> - Use "normals on" and "media on" in the radiosity settings. Use  
> high-quality settings, and/or turn sample caching off (requires UberPOV).
>
> - Don't use "filter" (unless you know what you're doing). Use a fading  
> interior instead, with "fade_power 1001", or use absorbing media.
>
> - Don't use "rainbow" (does anyone?).
>
> - Do use a little bit of reflection on all your materials (typically  
> with heavy blur).
>
> - If something doesn't look right, don't ask "what effect can I add or  
> tweak to make it look better?" but "what phyiscal properties of my scene  
> have I not modelled correctly?"
>
>
> As for HDR light probes, contrary to what Jerome wrote, the question of  
> whether they're legit as a /sky sphere/ to avoid complex modelling is  
> outside the scope of PBR; what's a no-go in PBR is using them for  
> /environment mapping/ to fake reflections, but POV-Ray doesn't support  
> that technique out of the box anyway. (You /could/ achieve a similar  
> effect and possibly some of the speedup by using a HDR sky sphere and  
> setting all objects to "no_reflection on", but environment mapping is  
> also frequently used with different maps for different objects.)
>
>
> The advantages of PBR are threefold:
>
> - It takes far less time to achieve a convincing result, provided you  
> have a basic understanding of the the underlying physical effects,  
> because you don't need endless iterations of tweaking your material and  
> light source parameters, repeatedly trying to figure out (A) what's  
> still wrong about the resulting image, and (B) how to counter this with  
> the knobs available (without introducing other undesired effects). With  
> PBR, first of all your images will /always/ be physically consistent in  
> themselves (and thus convincing in a very basic sense), and second, all  
> you need to achieve a truly convincing look is to carefully examine the  
> materials and light sources you intend to model and plug in the  
> corresponding values. If you did it right, all you have left to do is  
> worry about whether the image is pleasing, not whether it is convincing.
>
> - You can freely combine elements from different sources. In a non-PBR  
> environment, only the combination of materials and lighting can be  
> assessed for whether they are convincing or not, and any attempt to set  
> up some "neutral" setting to assess just one or the other is moot: To  
> assess whether a lighting setup is "neutral" it would have to be tested  
> with known "neutral" materials, but to assess whether a material is  
> "neutral" in the first place it would have to be tested with a known  
> "neutral" lighting setup - a classic hen and egg problem. In practice,  
> different authors will inevitably have different ideas what a chicken  
> actually is. In a PBR environment, however, a material can be assessed  
> simply by checking whether the parameters plugged in match the optical  
> characteristics observed in reality, without rendering even a single  
> image, and the same goes for lighting setups. So even if you don't have  
> the facilities to measure the exact optical chracteristics of all your  
> materials and lighting setups, you can jump-start your chicken farm from  
> a small set of precisely known materials and lighting setups.
>
> - You can rely on the results being physically accurate, allowing you to  
> model scenes for which you have no real-life reference image to go by.  
> (Maybe one of the most spectacular examples is the black hole and  
> accretion disk in the "Interstellar" movie, which was modeled solely  
> from physical principles - at least as far as the distortion of  
> spacetime is concerned - rather than preconceived notions of how such a  
> phenomenon would look like.)
>


-- 
-Nekar Xenos-

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