Hey all,

I've been thinking about making a mega_metals.inc based on official POV's
metals.inc to include Blinn highlights and reflect_metallic.  A few
questions:

A) Is there an easy way to calculate the amounts of "blinn" and "facets"
based on the old "specular" and "roughness" values?  I've changed F_MetalA
and been tweaking the numbers for about a half hour and would like to avoid
having to use trial and error for the other 4 finishes.

2) Should I take out the "specular" and "roughness" statements, or leave
them in (modified?)?  Again, tweaking could probably produce decent results.

III) Should I take out the "metallic" when I put in "reflect_metallic"?
I've tried it both ways and can get decent results with enough tweaking.

See picture in binaries.images (same subject) for a sample picture.

Any hints, suggestions, flames or insults would be appreciated.

Eric
--------------------
http://www.datasync.com/~ericfree
--------------------
"The whole problem with the world is that fools and fanatics are always so
certain of themselves, but wiser people so full of doubts."
--Bertrand Russel

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I tried the blinn highlight but didn't see much difference with specular.
I didn't see why it's more realistic or better.
  Could someone post an image (to p.b.i) clearly showing the difference
between specular and blinn in the same object?

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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"Nieminen Juha" <war### [at] punarastascstutfi> wrote in message
news:3897f7b4@news.povray.org...
>
>   I tried the blinn highlight but didn't see much
> difference with specular.  I didn't see why it's
> more realistic or better.

After several hours of tweaking I've come to the same conclusion.  My "best"
results look just like the old metals.  But, hey, I don't have to get up
early tomoro.  Wait... I ****DO**** have to get up early tomoro.

<ScoobyDoo voice>
Ruh Roh.
</ScoobyDoo voice>

Eric
--------------------
http://www.datasync.com/~ericfree
--------------------
"The whole problem with the world is that fools and fanatics are always so
certain of themselves, but wiser people so full of doubts."
--Bertrand Russel

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Eric Freeman <eri### [at] datasynccom> wrote...
> 2) Should I take out the "specular" and "roughness" statements, or leave
> them in (modified?)?  Again, tweaking could probably produce decent
results.

You should take out specular if you want to use blinn.

> III) Should I take out the "metallic" when I put in "reflect_metallic"?
> I've tried it both ways and can get decent results with enough tweaking.

You should use both metallic and reflect_metallic.  metallic affects the
color of the highlight, while reflect_metallic affects the color of
reflected rays.

-Nathan

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Nieminen Juha <war### [at] punarastascstutfi> wrote...
>   I tried the blinn highlight but didn't see much difference with
specular.
> I didn't see why it's more realistic or better.
>   Could someone post an image (to p.b.i) clearly showing the difference
> between specular and blinn in the same object?

Honestly, I didn't see much of a difference either.  However, blinn
highlights are a much better estimate for some surfaces, and are based on
statistics and physical properties.  Specular and phong are just estimates.

Basically, when people created the specular and phong models, the said, "The
surface looks like this.  How can I design my model so it produces similar
output."  So both of those models are just guesses that look fairly good.

When people created torrance+sparrow+blinn+cook highlight model, they said,
"On the microscopic level, we can describe the surface like this.  If the
surface does look like that, then we can use statistics, coupled with the
fresnel reflectivity function to determine how much light is reflected back
for each angle.  Then, if we did our math correctly, our model will produce
output that looks real."

The differences between blinn and specular are subtle, but then again,
motion blur, focal blur, and radiosity are all subtle when used correctly,
and they can add a lot to realism.

-Nathan

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"Nathan Kopp" <Nat### [at] Koppcom> wrote in message
news:38982a08@news.povray.org...
>
> Eric Freeman <eri### [at] datasynccom> wrote...
> > 2) Should I take out the "specular" and "roughness" statements, or leave
> > them in (modified?)?  Again, tweaking could probably produce decent
> results.
>
> You should take out specular if you want to use blinn.
>
> > III) Should I take out the "metallic" when I put in "reflect_metallic"?
> > I've tried it both ways and can get decent results with enough tweaking.
>
> You should use both metallic and reflect_metallic.  metallic affects the
> color of the highlight, while reflect_metallic affects the color of
> reflected rays.
>
> -Nathan

Thanks.  After playing around with different values, I'm beginning to see
some differences between the two.  If I get the copper metal looking the
same for the old and new methods, then switch just the pigment to silver or
brass, the old and new method no longer look the same.  I guess I'll just
make five finishes going from dull to shiney.

Eric
--------------------
http://www.datasync.com/~ericfree
--------------------
"The whole problem with the world is that fools and fanatics are always so
certain of themselves, but wiser people so full of doubts."
--Bertrand Russel

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