clipka <ano### [at] anonymousorg> wrote:
> Am 06.04.2016 um 14:06 schrieb And:
> > clipka <ano### [at] anonymousorg> wrote:
> >> Am 06.04.2016 um 09:52 schrieb And:
> >>
> >>> I derived a solution on what I said the albedo value getting dark when sigma
> >>> increase.
> >>> I study the formula from the wikipedia. It said A=1-0.5*..., B=0.45*...(Both
> >>> rely on the sigma)
> >>>
> >>> And the result albedo seems rho*A + rho*B*(2/3-64/45/pi) instead rho
> >>> itself. So maybe you can divide it when apply the diffuse albedo feature.
> >>
> >> Thanks! That correction factor appears to make a lot more sense than the
> >> hack I had come up with :)
> >>
> >> Not too surprisingly, experiments indicate that it does indeed fit like
> >> a glove.
> >
> > Ok ok! cheers.
> >
> > If I don't make mistake. but it should correct because I calculate formula
> > carefully.
>
> Actually, once I thought about your result, I realized that the
> bihemispherical albedo /must/ be
>
>     rho*( A*a + B*b )
>
> with the terms A and B depending on sigma as specified in the Oren-Nayar
> description, and a,b being constant.
>
> From the fact that Oren-Nayar includes the Lambertian model as a special
> case with A=1,B=0 it follows that a /must/ be 1.
>
> The value 2/3+(64/45)*(1/pi) for b looks a bit complicated, but
> experiments with high sigma clearly indicate that it indeed at least
> approximates the proper value very closely, and it looks plausible
> enough as an exact value, so I'm pretty sure you did indeed get the
> hemispherical integral right.

Well. :)




"Bald Eagle" <cre### [at] netscapenet> wrote:
> Sometimes I read these threads and wonder when "POV-Ray version QED" will be
available:

QED... I think that is far from the rendering application.

>
> https://www.youtube.com/watch?v=eLQ2atfqk2c&list=PL8590A6E18255B3F4
>
> I must confess, I watched the whole thing, and I found it fascinating, because
> he says things about the behaviour of light that I've always wondered about, and
> that they Never Ever mentioned in my entire academic experience, which was very
> long and very painful   ;)
Well.

>
> I think it's excellent that a new diffuse reflection model is being experimented
> with - I'm sure there ought to be some interesting technical and artistic works
> appearing in short order.

Oren-Nayar reflection model is a very useful feature for me.

Post a reply to this message