# [Bf-cycles] build with OSL support

Brecht Van Lommel brechtvanlommel at pandora.be
Mon Nov 14 18:16:25 CET 2011

```Patch committed to svn, thanks!

Brecht.

On Sat, Nov 12, 2011 at 4:20 PM, Yasuhiro Fujii
<y-fujii at mimosa-pudica.net> wrote:
> The O-N patch updated. This should be last update...
>
> The meaning of roughness has changed again from last mail.
> It is still simple formula and keeps the range [0, 1].
> It keeps overall intensity invariant when changing the roughness.
> I think orthogonality of the parameters is very important for the usability.
> Additionally, you can always obtain the same result as original O-N's
> to adjust the roughness and color values (but it is not a trivial
> transformation).
>
> The detail is below (copy & paste from source code).
> /*
> * NOTE:
> * BSDF = A + B * cos() * sin() * tan()
> *
> * The parameter sigma means different from original.
> * A and B are calculated by the following formula:
> * A = (3 - sigma) * (1/3pi)
> * B = sigma * (2/3pi)
> *
> * This formula is derived from following conditions:
> *
> * 0. Normalize A-term and B-term *individually*.
> * B-term is normalized at maximum point: dot(L, N) = 0.
> * A = (1/pi) * A'
> * B = (2/pi) * B'
> *
> * 1. Blend A-term and B-term linearly so that
> * A' + B' = 1
> * B == 0 if sigma == 0
> * A == B if sigma == 1
> */
>
> On Fri, Nov 11, 2011 at 8:48 PM, Brecht Van Lommel
> <brechtvanlommel at pandora.be> wrote:
>> On Fri, Nov 11, 2011 at 10:53 AM, Yasuhiro Fujii
>> <y-fujii at mimosa-pudica.net> wrote:
>>> I want to propose simpler ones:
>>>  0<= sigma <= 1
>>>  A = 1.0f - 0.5f * sigma;
>>>  B = 0.5f * sigma;
>>> which are much more useful for me. they have no magic numbers and
>>> behave straightforwardly.
>>> Of course, this form is artificial. however, original form also
>>> doesn't seem to have strong theoretical reason. It seems to be chosen
>>> by numerical experiment, not by the straight approximation.
>>>
>>> What do you think about it?
>>
>> Looks like a good change, I've tried to keep things in 0..1 range in
>> other places too.
>>
>> Brecht.
>> _______________________________________________
>> Bf-cycles mailing list
>> Bf-cycles at blender.org
>> http://lists.blender.org/mailman/listinfo/bf-cycles
>>
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>
```