On 03/11/2011 12:06 PM, Aydan wrote:
> mm_per_unit is an attribute of the world (scene) not the object.

I understand the current implementation it just seems counter-intuitive
to me.

> If you scale an object with the same material it's SUPPOSED to look different,
> just like in the real world. If you want it to look the same when it's e.g.
> double the size you need to use a different (more translucent) material. So the
> logic as it is implemented makes absolute sense.

yep and I get that too ... that's why a too big of a value for
mm_per_unit presents a material that you can practically see through

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On 11/03/2011 4:06 PM, Aydan wrote:
> mm_per_unit is an attribute of the world (scene) not the object.
> If you scale an object with the same material it's SUPPOSED to look different,
> just like in the real world. If you want it to look the same when it's e.g.
> double the size you need to use a different (more translucent) material. So the
> logic as it is implemented makes absolute sense.

You won't get an argument from me, Aydan. ;-)

-- 
Regards
     Stephen

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On 11/03/2011 4:39 PM, Jim Holsenback wrote:
> On 03/11/2011 10:12 AM, Stephen wrote:
>> What I think we need to do is scale both the subsurface values and the
>> texture, independently but related. (If that makes sense)
>
> agreed ... I'm doing a beauty run on the stanford dragon now, here's
> what I have for the material:
>

I await in anticipation.

> object { stanford_dragon
> material {
>    texture {
>      T_Stone18
>      scale 0.035
>    finish {
>      subsurface {translucency<0.05,1,1>*0.5}
>      reflection { SeaGreen*0.001 }
>      }
>    }
>    interior {ior 1.62}
>    }
>

Hmm! I might try using coloured reflection sometime. 0.001 seems quite 
subtle. :-D

> I copied T_Stone18 into my scene file and made a couple of mods (ambient
> to 0 and dialed down diffuse a touch) in the bottom layer texture, then
> changed phong to specular/roughness on the outer layer.
>

T_Stone18 is quite dark. I can't wait to see it.

> To setup the sslt I used a plain white texture instead of T_Stone18
> while I dialed in the sslt (seems to help with visualizing the effect).

Sounds like a good idea.

> That was interesting because my 1st take on mm_per_unit was that it
> would be smaller than default because of the size of the model at scale
> 1. When smaller didn't seem to be working I tried default without much
> luck either, so I increased to 1000 then 2540, but still had to wildly
> scale the translucency color. Finally I decided to try a couple of half
> step itterations between something I considered to be more reasonable
> (100 - 10) and found the sweet spot. The value I arrived at was so close
> to the subsurface scene file values, I opted to use mm_per_unit 40 and
> quickly was able to tune the translucency setting to what's shown above.
>

"Suck it and see" technique. :-D

>> PS I notice that you forgot to put your subsurface values in the RC3
>> format :-P
>
> ha-ha ... bleeding edge :-P

I suppose that you deserve something for all your hard work on the docs.

-- 
Regards
     Stephen

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On 03/11/2011 01:06 PM, Stephen wrote:
>> That was interesting because my 1st take on mm_per_unit was that it
>> would be smaller than default because of the size of the model at scale
>> 1. When smaller didn't seem to be working I tried default without much
>> luck either, so I increased to 1000 then 2540, but still had to wildly
>> scale the translucency color. Finally I decided to try a couple of half
>> step itterations between something I considered to be more reasonable
>> (100 - 10) and found the sweet spot. The value I arrived at was so close
>> to the subsurface scene file values, I opted to use mm_per_unit 40 and
>> quickly was able to tune the translucency setting to what's shown above.
>>
> 
> "Suck it and see" technique. :-D

ha-ha ... yes as I mentioned in another thread it seems a bit like
aligning a piece of electronic equipment ... hey it works for me but I'm
a rather odd duck about some things ;-)

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On 11/03/2011 5:24 PM, Jim Holsenback wrote:
>> "Suck it and see" technique.:-D
> ha-ha ... yes as I mentioned in another thread it seems a bit like
> aligning a piece of electronic equipment ... hey it works for me but I'm
> a rather odd duck about some things;-)
>

What difficult about aligning electronic equipment, ducky?

-- 
Regards
     Stephen

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> On 03/11/2011 04:25 AM, clipka wrote:
>> Am 10.03.2011 16:15, schrieb Jim Holsenback:
>>> On 03/10/2011 11:01 AM, Stephen wrote:
>>>> I'm sure that the last value overwrites the first.
>>>
>>> That was my 1st thought as well, but considering that you're able to
>>> declare a default texture/pigment/finish at different places and have to
>>> applied accordingly, I thought it was worth asking :-)
>>
>> Note that mm_per_unit it is a global_setting, not a default ;-)
>
> Yep ... realize that. I guess /global/ should have been my 1st clue ...
> eh? While we're on the subject, having mm_per_unit in globals just seems
> counter-intuitive. I'm sure there's a technical reason for having it
> there, or maybe when the feature was implemented it just wasn't
> considered that there could be a case of having more than one sslt
> object of different scale in a scene. Since scaling (generalized NOT
> sslt) is either attached to a material, texture, pigment or object
> wouldn't it make more sense to have it on a per object bases ie:
>
> object {
>    ....
>    finish {
>      subsurface { translucency color mm_per_unit float }
>      }
>    }

When you scale an object containing some media, the media's aspect 
changes as the amount of media does change. It's the expected behaviour.

When you scale an object with interior fading, the apearance also change 
as there is now more or less material involved. Also an expected behaviour.

In both cases, if you want the effect to remain the same, you need to 
also scale those features. Increase or deduce the media density, scale 
the fade_distance, accordingly to the new dimentions of the object.

Exactly the same apply to any object using SSLT. Here also, it should 
the expected behaviour. The effect is dimention dependent.




Alain

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On 03/11/2011 03:23 PM, Alain wrote:
> When you scale an object containing some media, the media's aspect
> changes as the amount of media does change. It's the expected behaviour.
> 
> When you scale an object with interior fading, the apearance also change
> as there is now more or less material involved. Also an expected behaviour.

thanks ... this ties it together better for me (volume)

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