clipka <ano### [at] anonymousorg> wrote:
> Am 05.04.2016 um 14:50 schrieb And:
> > "And" <49341109@ntnu.edu.tw> wrote:
> >> clipka <ano### [at] anonymousorg> wrote:
> >>> Am 31.03.2016 um 19:27 schrieb clipka:
> >>>
> >>>
> >>> - My implementation of the Oren-Nayar model turns out to be bugged.
> >>>
> >>
> >> I like the feature, could I help test it? I have read this model on wikipedia
> >> and thought about it for a while.
> >
> > I just tried your new texture. The bigger the sigma the surface appears darker
> > when applying the same diffuse value. It is from the Oren-Nayar model itself I
> > have confirmed.
> >
> > Is this the bug you said?
>
> No; since it's an intrinsic property of the model, I don't consider it a
> bug.
>
> What I got wrong is the dependence on "sideways" illumination, if you
> know what I mean.
>
> In the model there's a term depending on the angle between the light
> source and eye directions /projected/ onto the surface (the azimuth
> angle, if you like). Normally I should compute the projected vectors,
> normalize them, and compute the dot product, to get the cosine of the
> angle. But I forgot the normalization step.


OkOK. That sounds very easy to fix for you.

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.

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