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Am 23.06.2015 um 19:04 schrieb Nekar Xenos:
> I am assuming PBR in games doesn't do ray-tracing, so why do they call it
> Physically Based Rendering in games. Even Space Engineers has PBR now.
After having googled a bit, it seems that in DirectX 11 parlance, the
buzzword "PBR" is used in a more basic sense:
(1) Perform colour computations on linear values rather than
gamma-compressed ones (in POV-Ray terms, use "assumed_gamma 1.0"). It
seems that the gaming world is only just now realizing that they've been
applying their math to the wrong type of values, and that they need to
do more about gamma than just giving us that infamous "gamma" slider to
adjust the output image to our display gamma (and that using proper
gamma handling really adds to realism - or, in other words, that the
failure to do so has been a serious limit to realism).
(2) Use high dynamic range material for environment maps.
(3) Discard the dated Blinn-Phong model for specular highlights in
favour of the Cook-Torrance model:
(3a) Make sure that the brightness of specular highlights is within
physically reasonable bounds. (In POV-Ray, this can easily be achieved
by using the "albedo" keyword.)
(3b) Make the brightness of specular highlights (and maybe also
environment maps for reflection?) dependent on the angle of incidence
according to the Fresnel function. (For non-metallic materials, this one
has only recently been added to POV-Ray as well, by allowing to use
"fresnel on" in the entire finish block. However, POV-Ray goes even one
step further there, and also modulates the diffuse component
accordingly, which the gaming industry apparently doesn't. On the other
hand the gaming industry seems to be going for a GGX-based version of
Cook-Torrance, while POV-Ray is still stuck with a Phong- or
Blinn-Phong-based version.)
(3c) For metallic materials, make sure that the specular highlights have
the same colour as the diffuse component. (In POV-Ray this has been part
of the package for ages, by using "metallic on".)
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