POV-Ray : Newsgroups : povray.newusers : Metal textures Server Time: 16 Jun 2019 07:23:30 GMT
  Metal textures (Message 1 to 9 of 9)  
From: aradan d
Subject: Metal textures
Date: 11 Dec 2015 09:30:01
Message: <web.566a96f5bbd647149b2ba7d0@news.povray.org>
Hi,

is there a webpage where I can learn how to make more realistic metal textures?
I was trying to do

#declare f_metal = finish {
    ambient .2 diffuse .4
    specular 1.8 roughness .08 brilliance 2
    reflection { .8 metallic 1 } metallic
    irid {0.2}
}

....

sphere {
        <0, 0, 0>, 0.8
        material {
            texture {
                T_Chrome_1B
                finish {
                    f_metal
                }
            }
        }
}
....


but I'm not convinced by the result, it does not look like proper metal. I have
seen some images in the forum which look nice, but the usually do not provide
the pov file, at least I am missing something


Regards


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From: Cousin Ricky
Subject: Re: Metal textures
Date: 11 Dec 2015 12:25:01
Message: <web.566ac01626c2efd3fd54400e0@news.povray.org>
"aradan.d" <ara### [at] gmailcom> wrote:
>
> #declare f_metal = finish {
>     ambient .2 diffuse .4
>     specular 1.8 roughness .08 brilliance 2
>     reflection { .8 metallic 1 } metallic
>     irid {0.2}
> }

Diffuse + reflection should never be greater than one, and your ambient value
seems too high.  Ambient should scale down with diffuse as reflection
increases--i.e., the ambient-to-diffuse ratio should be the same for all
textures in a given scene.

RC3Metal in the Object Collection ( http://lib.povray.org/ ) will do these
adjustments for you, as well as coordinating specular, roughness, and
brilliance.

According to Clipka (one of the POV-Ray developers), realistic metals should
have ambient 0 diffuse 0 and use blurred reflection.  Blurred reflection is not
built into POV-Ray, but it is available with UberPOV and RC3Metal.  The
knowledge base (
http://wiki.povray.org/content/Knowledgebase:POV-Ray_Questions_and_Tips )
describes a technique for blurred reflection, but it can trigger eternal render
times if you're not careful.  This problem is also remedied in RC3Metal.

(Do not use metals.inc and golds.inc as models.  Those files were written for
ancient versions of POV-Ray and are essentially obsolete.)


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From: Le Forgeron
Subject: Re: Metal textures
Date: 11 Dec 2015 13:07:12
Message: <566aca80$1@news.povray.org>
And I would add : the environment is very important.

a metal rod in deep space does not look the same that the same rod in a lab.


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From: clipka
Subject: Re: Metal textures
Date: 11 Dec 2015 15:37:56
Message: <566aedd4$1@news.povray.org>
Am 11.12.2015 um 10:27 schrieb aradan.d:
> Hi,
> 
> is there a webpage where I can learn how to make more realistic metal textures?
> I was trying to do

The essence of getting realistic metal textures can be summed up in
three rules:

#1: Create some environment for the texture to reflect.
#2: Create *more* environment for the texture to reflect.
#3: Make the texture reflective.


Aside from that, there are some things that can improve the realism of
the texture:

#4: Use the "metallic" keyword, both in the "finish" block itself and in
the "reflection" block.

#5: Explicitly use "ambient 0", and use "emission 0" (which is the
default for the latter setting). If you think any other value for these
parameters makes your texture look metallic, it is probably a hint that
you didn't follow rule #2 properly.

#6: Use "specular albedo X" rather than just "specular X"; this makes it
much more easy to follow the next rule.

#7: Make sure the "specular" parameter matches the "reflection"
parameter; if you're using the "specular albedo" construct, both the
specular and reflection parameter should have the same value.

#8: Make sure the dullness of the specular highlights matches that of
the reflections. If you're using UberPOV, this means that you should
specify "roughness" in the "reflection" block as well, using the same
value as in the "finish" block; if you're using regular POV-Ray, it
means that you should ideally specify a very low "roughness", and use
some different mechanism if you want to achieve a less polished look
(ask about "micronormals" or "macronormals"). Alternatively and only as
a last resort, ditch the reflection and highlights altogether and use
only diffuse instead, going for a very dull look.

#9: Explicitly use "diffuse 0", unless you're trying to wiggle your way
around rule #8.


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From: aradan d
Subject: Re: Metal textures
Date: 11 Dec 2015 18:40:03
Message: <web.566b185b26c2efd349882bdf0@news.povray.org>
Thanks for this. I will try the RC3Metal.
Clipka also gave very good tips for getting metal finishes, so I will also
follow them.

In the object collection, most of the files are very old, are there
more recent resources on Povray? I have googled a lot, but most of
the webpages are from the early 2000s and look outdated :(


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From: Sherry K  Shaw
Subject: Re: Metal textures
Date: 12 Dec 2015 06:32:05
Message: <566bbf65$1@news.povray.org>
Here's a question--

I haven't yet taken the time* to experiment much with the new features 
of 3.7 in regard to specifically metallic textures,** but now I'm 
curious--has "brilliance" been affected by the changes to the finish 
statement, and, if so, how?  Because it strikes me that brilliance has 
been an important component of metallic textures for quite a while, 
possibly twenty years or so--oh, good God, have I been Povving THAT 
long?  Oh, dear lord, I'm old!  OLD!

Just curious,

--Sherry Shaw

* Because, hey, life.

** I've pretty much just played around with subsurface scattering as a 
route to making more realistic cheese.  Imagine a Stanford bunny carved 
from a nice Vermont aged white cheddar.  Mmmm, cheeeeese.

-- 
#macro T(E,N)sphere{x,.4rotate z*E*60translate y*N pigment{wrinkles scale
.3}finish{ambient 1}}#end#local I=0;#while(I<5)T(I,1)T(1-I,-1)#local I=I+
1;#end camera{location-5*z}plane{z,37 pigment{granite color_map{[.7rgb 0]
[1rgb 1]}}finish{ambient 2}}//                                   TenMoons


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From: clipka
Subject: Re: Metal textures
Date: 12 Dec 2015 13:00:38
Message: <566c1a76@news.povray.org>
Am 12.12.2015 um 07:32 schrieb Sherry K. Shaw:
> Here's a question--
> 
> I haven't yet taken the time* to experiment much with the new features
> of 3.7 in regard to specifically metallic textures,** but now I'm
> curious--has "brilliance" been affected by the changes to the finish
> statement, and, if so, how?  Because it strikes me that brilliance has
> been an important component of metallic textures for quite a while,
> possibly twenty years or so--oh, good God, have I been Povving THAT
> long?  Oh, dear lord, I'm old!  OLD!

"Brilliance" has been affected insofar as it now interacts with the
effective diffuse brightness /if/ you use the new "diffuse albedo FLOAT"
syntax.

Using the traditional "diffuse FLOAT" syntax, the parameter value
directly specifies the /maximum/ brightness of the diffuse reflection,
i.e. the apparent brightness of the surface when looking at it exactly
perpendicular; the "brilliance" keyword only affects the apparent
brightness when looking at the surface from a more shallow angle.

Using the new "diffuse albedo FLOAT" syntax, the parameter value
specifies the /total/ brightness of the diffuse reflection, integrated
over the entire hemisphere. At the default brilliance of 1.0, this has
the same effect as the old "diffuse FLOAT"; however, as brilliance
increases and the diffuse reflection "tightens", this now increases its
/maximum/ brightness.


That said, the use of "diffuse" (and, by extension, "brilliance") in
metallic textures has no physical justification, and is only there
because back then the primary approach to designing textures was to
tweak them until the author thought it looked as realistic as he could
possibly manage, rather than starting from principles of physics.

As for using "brilliance" in metallic textures, it makes the diffuse
component appear more highlight-ish, and highlights are what our brain
expects from metallic surfaces.


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From: William F Pokorny
Subject: Re: Metal textures
Date: 12 Dec 2015 16:24:57
Message: <566c4a59$1@news.povray.org>
On 12/11/2015 01:39 PM, aradan.d wrote:
> Thanks for this. I will try the RC3Metal.
> Clipka also gave very good tips for getting metal finishes, so I will also
> follow them.
>
> In the object collection, most of the files are very old, are there
> more recent resources on Povray? I have googled a lot, but most of
> the webpages are from the early 2000s and look outdated :(
>
>

How about a short set of web sites I reference old and new. :-)

Like any tool around a long time, many POV-Ray reference sites have been 
around a while too & that is OK. Much of the old information is still 
valid. Remember too, there are users still running versions earlier than 
3.7. The difficultly, of course, is in some places like gamma, color 
space handling & finish, things have changed for the better over time & 
if running the latest code, often some adaptation of the older 
references is required.

An overview of the 3.7 changes can be found in the documentation : 
http://www.povray.org/documentation/3.7.0/t2_1.html#t2_1_4_1

--- Some ref sites
http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Render/POV-Ray/Sample_Materials
http://www.econym.demon.co.uk/isotut/index.htm
http://www.f-lohmueller.de
http://www.ignorancia.org
http://www.imagico.de/raytracing_en.php
    (See too http://earth.imagico.de/main.php because it's cool)
http://www.lilysoft.org/
http://www.oyonale.com
https://commons.wikimedia.org/wiki/Category:Created_with_Persistence_of_Vision
https://sites.google.com/site/poseray

There are too some youtube tutorial videos, but I confess to never 
having viewed them being an older user.

--- Old/New Image competitions - often with source code / how created 
information.
http://www.tc-rtc.co.uk/
http://www.irtc.org/  Dead, but has links to old images & files.

--- Don't forget http://www.povray.org wiki etc. Especially use the site 
search.

Much information is posted to various news groups and in addition to the 
web search above these can searched with newsreader tools like Thunderbird.

For example, a povray.binaries.scene-files post I've been working 
through over the past year plus is Norbert Kern's 300(+) Materials posting.

http://news.povray.org/povray.binaries.scene-files/thread/%3Cweb.53b015a68c7b99427ffb57fd0@news.povray.org%3E/

Norbert has compiled a great many useful textures from years past in one 
place. It's a great reference. Further, he's done an admirable job of 
moving many old materials/textures - including some metals - into the 
3.7 realm. That said, he uses the older style 2.2 gamma by default and 
not all materials I've tried map well to a working gamma of 1.0.

I'm hinting through this last example that even new/3.7 references often 
enough require tweaking for use in any particular scene in POV-Ray.

Hope something in my rambling a help.

Bill P.


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From: Sherry K  Shaw
Subject: Re: Metal textures
Date: 12 Dec 2015 20:04:36
Message: <566c7dd4$1@news.povray.org>
clipka wrote:
> Am 12.12.2015 um 07:32 schrieb Sherry K. Shaw:
>
> That said, the use of "diffuse" (and, by extension, "brilliance") in
> metallic textures has no physical justification, and is only there
> because back then the primary approach to designing textures was to
> tweak them until the author thought it looked as realistic as he could
> possibly manage, rather than starting from principles of physics.
>
> As for using "brilliance" in metallic textures, it makes the diffuse
> component appear more highlight-ish, and highlights are what our brain
> expects from metallic surfaces.
>

Ah...so with the proper application of rules #6 through #9 above, what 
used to be "brilliance" is now thoroughly covered by the proper use of 
highlights and reflection...?

Must study further; good excuse to make some pictures.  :)

Thanks!

--Sherry Shaw

-- 
#macro T(E,N)sphere{x,.4rotate z*E*60translate y*N pigment{wrinkles scale
.3}finish{ambient 1}}#end#local I=0;#while(I<5)T(I,1)T(1-I,-1)#local I=I+
1;#end camera{location-5*z}plane{z,37 pigment{granite color_map{[.7rgb 0]
[1rgb 1]}}finish{ambient 2}}//                                   TenMoons


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