On 15-2-2012 17:51, andrel wrote:

> I agree. When the skin is so wet, you would expect small 'puddles' in
> places where they can collect and droplets at overhangs like the chin.

Indeed. I did the test on myself :-)

>
> If it is intended as oil, most of us seldom seen females fully oiled (I
> am told it happens at the sort of parties that we never attend). Hence
> it is unfamiliar and therefore unconvincing.
Eerr... I do not want to give the impression that I... well, I mean... ;-)

To be serious: I fully agree and I indeed wanted to test the 
(exagerated) image on unsuspecting viewers because I was not entirely 
sure how to proceed in this case.

Thanks all for the comments! In time, I shall investigate the wet skin 
further (a longer term goal) but if anybody comes up with something 
before please show and teach us.

Thomas

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Am 14.02.2012 08:53, schrieb Thomas de Groot:

>> Don't worry about it: You can't get it right anyway, due to a known
>> problem with POV-Ray's implementation of UV-mapped image-based bump
>> maps. Unfortunately, fixing it isn't exactly trivial.
>
> Ah? Interesting to hear this. I hope (I know!) you will find a solution.

My last attempt to fix it came at the cost of scrambling all 
non-UV-mapped bump maps instead, for reasons I didn't quite understand :-P

But be sure I'll try again; it's one of the things that currently bug me 
most about POV-Ray.

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Am 14.02.2012 08:53, schrieb Thomas de Groot:
> On 14-2-2012 1:13, clipka wrote:
>> Am 13.02.2012 13:25, schrieb Thomas de Groot:
>>
>>> I am still not sure about whether the bump sizes should be positive or
>>> negative. I find positive values looking better in general but that
>>> might be a wrong approach.
>>
>> Don't worry about it: You can't get it right anyway, due to a known
>> problem with POV-Ray's implementation of UV-mapped image-based bump
>> maps. Unfortunately, fixing it isn't exactly trivial.
>
> Ah? Interesting to hear this. I hope (I know!) you will find a solution.

I'm currently looking into this once again. Seems like there are 
actually two more-or-less independent design flaws contributing to this, 
one of which affects even non-UV-mapped bump maps.

And then tnere's another one, that has gone unnoticed so far: Did you 
know that if you use a low-resolution bump map for testing, you'll get 
stronger bumps than in the final render?

This also means that if I sort out all the problems, I'm guaranteed to 
break each and every existing scene that uses bump maps. Yuck!

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On 12-3-2012 3:40, clipka wrote:
> Am 14.02.2012 08:53, schrieb Thomas de Groot:
>> On 14-2-2012 1:13, clipka wrote:
>>> Am 13.02.2012 13:25, schrieb Thomas de Groot:
>>>
>>>> I am still not sure about whether the bump sizes should be positive or
>>>> negative. I find positive values looking better in general but that
>>>> might be a wrong approach.
>>>
>>> Don't worry about it: You can't get it right anyway, due to a known
>>> problem with POV-Ray's implementation of UV-mapped image-based bump
>>> maps. Unfortunately, fixing it isn't exactly trivial.
>>
>> Ah? Interesting to hear this. I hope (I know!) you will find a solution.
>
> I'm currently looking into this once again. Seems like there are
> actually two more-or-less independent design flaws contributing to this,
> one of which affects even non-UV-mapped bump maps.

Excellent! I mean, you looking into the matter ;-)
>
> And then tnere's another one, that has gone unnoticed so far: Did you
> know that if you use a low-resolution bump map for testing, you'll get
> stronger bumps than in the final render?

Well, I may have noticed but not consciously really.

>
> This also means that if I sort out all the problems, I'm guaranteed to
> break each and every existing scene that uses bump maps. Yuck!

Who cares? :-) I am quite willing to redo everything as long as 
henceforward everything works better.

Thomas

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Am 16.02.2012 15:46, schrieb clipka:
> Am 14.02.2012 08:53, schrieb Thomas de Groot:
>
>>> Don't worry about it: You can't get it right anyway, due to a known
>>> problem with POV-Ray's implementation of UV-mapped image-based bump
>>> maps. Unfortunately, fixing it isn't exactly trivial.
>>
>> Ah? Interesting to hear this. I hope (I know!) you will find a solution.
>
> My last attempt to fix it came at the cost of scrambling all
> non-UV-mapped bump maps instead, for reasons I didn't quite understand :-P
>
> But be sure I'll try again; it's one of the things that currently bug me
> most about POV-Ray.

Okay, here's a quiz to all of you: Please describe the surface structure 
of this thing. Are those dimples or pimples? (Hint: The light comes 
almost straight from the camera position.)

(Rendered with POV-Ray 3.7.RC5 using a  plain old non-uv-mapped 
bump_map; POV-Ray 3.6 gives the same results.)

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Preview of image 'bump_map_types.png'

Am 15.03.2012 20:53, schrieb clipka:
> Am 16.02.2012 15:46, schrieb clipka:
>> Am 14.02.2012 08:53, schrieb Thomas de Groot:
>>
>>>> Don't worry about it: You can't get it right anyway, due to a known
>>>> problem with POV-Ray's implementation of UV-mapped image-based bump
>>>> maps. Unfortunately, fixing it isn't exactly trivial.
>>>
>>> Ah? Interesting to hear this. I hope (I know!) you will find a solution.
>>
>> My last attempt to fix it came at the cost of scrambling all
>> non-UV-mapped bump maps instead, for reasons I didn't quite understand
>> :-P
>>
>> But be sure I'll try again; it's one of the things that currently bug me
>> most about POV-Ray.
>
> Okay, here's a quiz to all of you: Please describe the surface structure
> of this thing. Are those dimples or pimples? (Hint: The light comes
> almost straight from the camera position.)
>
> (Rendered with POV-Ray 3.7.RC5 using a plain old non-uv-mapped bump_map;
> POV-Ray 3.6 gives the same results.)

... and now with some patch.

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Attachments:
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Preview of image 'bump_map_types.png'

Le 15/03/2012 20:55, clipka nous fit lire :

> ... and now with some patch.

Hey, stop that (not)! How are we going to emulate the classical picture
of Escher with holes/spheres on a path ?

I guess that fix that issue, right ?

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Am 15.03.2012 22:44, schrieb Le_Forgeron:
> Le 15/03/2012 20:55, clipka nous fit lire :
>
>> ... and now with some patch.
>
> I guess that fix that issue, right ?

Unfortunately this is only half of the job: With this fix, bump maps 
will behave like all other perturbed normals - which means that they're 
still acting similarly weird when UV-mapped. That'll be the next to tackle.

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Am 15.03.2012 23:23, schrieb clipka:
> Am 15.03.2012 22:44, schrieb Le_Forgeron:
>> Le 15/03/2012 20:55, clipka nous fit lire :
>>
>>> ... and now with some patch.
>>
>> I guess that fix that issue, right ?
>
> Unfortunately this is only half of the job: With this fix, bump maps
> will behave like all other perturbed normals - which means that they're
> still acting similarly weird when UV-mapped. That'll be the next to tackle.

... oh, and warps mess up perturbed normals, too.

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On 15-3-2012 20:53, clipka wrote:
> Okay, here's a quiz to all of you: Please describe the surface structure
> of this thing. Are those dimples or pimples? (Hint: The light comes
> almost straight from the camera position.)
>
> (Rendered with POV-Ray 3.7.RC5 using a plain old non-uv-mapped bump_map;
> POV-Ray 3.6 gives the same results.)

LOL! Both! Obviously showing the problem you were refering to.

Thomas

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