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2. (Fine Arts) The color or incrustation which age gives to works of art;
especially, the green rust which covers ancient bronzes, coins, and medals.
It is quite common to see a patina discoloration inside the cracks,
crevices, and deep folds on sculpture while it's surface maintains
more of the original material's coloration.
How would one apply this affect to a 3d object with proceedural methods
rather than relying upon complicated image maps ?
--
Ken Tyler - 1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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I would simply use a layered texture. It might be a good idea to use
UVPov so you can have filtering layers, though.
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A very clumsy way is to use a layered texture with the "patina" pattern
going from inside out with more opacity nearer the middle, like a spherical
or onion, then scaled to fit as well as possible. Not really good for
anything except roughly spherical or some other basic shape.
A real good way, if it could be done, would be to use the object itself as
the pattern somehow. Only thing I can think of that might come close would
be a media-filled one scaled appropriately to hug the surface of the
original object. Maybe same could be done by using fade_distance in a
semi-transparent copy too. I just can't imagine fitting them together well
enough.
I'm just brain-storming (hazy sky, more like) because I've always liked the
idea of following the contours of a surface and applying that antiquing
effect. Nothing tangible has ever come of it, so I'm all ears.
Bob
Ken <tyl### [at] pacbell net> wrote in message
news:38158BD5.F0F02B93@pacbell.net...
>
>
> 2. (Fine Arts) The color or incrustation which age gives to works of art;
> especially, the green rust which covers ancient bronzes, coins, and
medals.
>
> It is quite common to see a patina discoloration inside the cracks,
> crevices, and deep folds on sculpture while it's surface maintains
> more of the original material's coloration.
>
> How would one apply this affect to a 3d object with proceedural methods
> rather than relying upon complicated image maps ?
>
>
> --
> Ken Tyler - 1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
> http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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Ken <tyl### [at] pacbellnet> writes:
> 2. (Fine Arts) The color or incrustation which age gives to works of art;
> especially, the green rust which covers ancient bronzes, coins, and medals.
>
> It is quite common to see a patina discoloration inside the cracks,
> crevices, and deep folds on sculpture while it's surface maintains
> more of the original material's coloration.
>
> How would one apply this affect to a 3d object with proceedural methods
> rather than relying upon complicated image maps ?
I'm not sure whether you're looking for an automatic generation of
patinas or a completely procedural approach. In the first case, you
should have a look at:
Modeling and Rendering of Metallic Patinas
Julie Dorsey and Pat Hanrahan
http://graphics.lcs.mit.edu/~dorsey/papers/patina/
I hope this helps
Thomas
--
http://thomas.willhalm.de/
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On Tue, 26 Oct 1999 04:09:09 -0700, Ken wrote:
>
>
>2. (Fine Arts) The color or incrustation which age gives to works of art;
>especially, the green rust which covers ancient bronzes, coins, and medals.
>
> It is quite common to see a patina discoloration inside the cracks,
>crevices, and deep folds on sculpture while it's surface maintains
>more of the original material's coloration.
>
> How would one apply this affect to a 3d object with proceedural methods
>rather than relying upon complicated image maps ?
I have a SIGGRAPH article on just this subject. Combined with the reference
Thomas posted, it should do just what you want. The article is called
"Efficient Algorithms for Local and Global Accessibility Shading" and is
by Gavin Miller. It was published in the SIGGRAPH 1994 Proceedings, but
is not available online. It talks about how to texture objects based on
their accessibility to cleaning agents - deep ridges and cracks don't get
cleaned as effectively so they gather dirt (or corrosion) over time.
If someone wants to try to implement the techniques in this article, I'd
be happy to scan it and email it to one or two people. That's in the scope
of the ACM's copyright notice, I believe. Be warned that it isn't very
well suited to general objects like those in POV. It does have some good
suggestions for heightfields, spheres, and meshes, though.
And, just to satisfy your lust for links, here's one everyone should know:
http://www2.iro.umontreal.ca/~ratib/code/cg.htm
Besides the content, this link is interesting because it lets you link
deeply but it uses Javascript to reconstruct the original frame structure.
While you're there, pay special attention to the link for Computer Graphics
Publications - that's where I got the title info for this paper (I have the
Proceedings at home.)
(That one should keep even The Great Ken busy for a few hours...)
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The trick recently discovered by SamuelT in his "chipped paint" series in
p.b.i. could be used for that : create a pigment pattern and then associate a
pigment function as a normal with a properly defined color_map. When the two
match, it gives interesting results. Of course, it will work only with
simulated shallow cracks, not with real 3D crevices and other real surface
perturbations, like folds.
Gilles
Ken wrote:
> 2. (Fine Arts) The color or incrustation which age gives to works of art;
> especially, the green rust which covers ancient bronzes, coins, and medals.
>
> It is quite common to see a patina discoloration inside the cracks,
> crevices, and deep folds on sculpture while it's surface maintains
> more of the original material's coloration.
>
> How would one apply this affect to a 3d object with proceedural methods
> rather than relying upon complicated image maps ?
>
> --
> Ken Tyler - 1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
> http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
Post a reply to this message
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Ken wrote:
>
> 2. (Fine Arts) The color or incrustation which age gives to works of art;
> especially, the green rust which covers ancient bronzes, coins, and medals.
>
> It is quite common to see a patina discoloration inside the cracks,
> crevices, and deep folds on sculpture while it's surface maintains
> more of the original material's coloration.
>
> How would one apply this affect to a 3d object with proceedural methods
> rather than relying upon complicated image maps ?
Thank you people for your suggestions and links to possible solutions.
I have come to the conclusion that it would be very difficult if not
impossible with proceedural textures. The mesh painting utilties are
looking like a very real possibilty however...
--
Ken Tyler - 1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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Ken wrote:
>Thank you people for your suggestions and links to possible
>solutions. I have come to the conclusion that it would be
>very difficult if not impossible with proceedural textures.
>The mesh painting utilties are looking like a very real
>possibilty however...
>
I've never used it but would slope-dependent textures from the
superpatch be a possibility?
Ingo
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On 28 Oct 1999 11:25:33 -0400, ingo wrote:
>I've never used it but would slope-dependent textures from the
>superpatch be a possibility?
Even better would be a texture based on the second derivative
of the surface, but such a thing is hard to calculate.
--
These are my opinions. I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html
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Ron Parker wrote:
>Even better would be a texture based on the second derivative
>of the surface, but such a thing is hard to calculate.
>
ehm, could you explain this please, in laymens terms?
Ingo
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