This is my first success with my visibility pattern. It is supposed to 
be copper or a copper alloy with a patina on it, worn away in exposed 
areas. The syntax is simple, this is the code that produced this image:


#declare TestObj=
union {
   box {<-5,-1,-5>, < 5, 0, 5>}
   cylinder {< -2, 0, 0>, <-1, 3, 0>, 1}
   cylinder {< 0, 0, 0>, <-1, 3, 0>, 1}
   difference {
      sphere {< 1, 1, 0>, 1}
      cone {< 1, 1, 0>, 0, < 1, 1.75,-1>, 0.65}
   }
}
object {TestObj
   texture {
      pigment {color rgb < 0.6, 0.45, 0>}
      finish {
         reflection 0.35
         reflect_metallic
         metallic
         ambient 0 diffuse 0.6
      }
   }
   texture {
      pigment {visibility 200, object {TestObj}
//visibility SAMPLES, TARGET_OBJECT
         color_map {
            [0 color rgb < 0.15, 1, 0.75>]
            [0.1 color rgb < 0.15, 1, 0.75>]
            [0.6 color White transmit 1]
            [1 color White transmit 1]
         }
      }
   }
}

Time For Trace:    0 hours 11 minutes  26.0 seconds (686 seconds)
On a PowerPC G3 at 266MHz.
I had to make the object be specified as a parameter, otherwise it 
didn't work with CSG objects. I am not sure why, though. And a possible 
problem with this syntax: although it gives you more control over the 
objects that affect the pattern, you can't just define a texture and 
have it work for all objects. :-(

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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Attachments:
Download 'visibility.JPG' (8 KB)

Preview of image 'visibility.JPG'

>This is my first success with my visibility pattern. It is supposed to
>be copper or a copper alloy with a patina on it, worn away in exposed
>areas. The syntax is simple, this is the code that produced this image:
>I had to make the object be specified as a parameter, otherwise it
>didn't work with CSG objects. I am not sure why, though. And a possible
>problem with this syntax: although it gives you more control over the
>objects that affect the pattern, you can't just define a texture and
>have it work for all objects. :-(

Couldn't you just make two separate versions? One for non-CSG and one for
that specific purpose? Could you make an example with an isosurface? Oh, and
why didn't you name it "patina"?

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In article <389db4cf@news.povray.org>, "TonyB" 
<ben### [at] panamac-comnet> wrote:

> Couldn't you just make two separate versions? One for non-CSG and one for
> that specific purpose?

I just coded the necessary changes to make the object parameter 
optional, it uses the object it is applied to when it isn't specified.


> Could you make an example with an isosurface?

I could. I haven't tested it with an isosurface yet, I hope it doesn't 
interact badly with the solving method.


> Oh, and why didn't you name it "patina"?

Because it can be used for more than just patinas. It can be used for 
anything that can be worn off: paint, maybe accumulations of dust, it 
might be good for landscapes....
Another good name might have been accessibility.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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That is pretty cool! I was just reading about something like that in
Scientific American magazine...About virtual weathering.  I don't know
if anyone has brought this up before, but the article is at:

http://www.sciam.com/2000/0200issue/0200dorsey.html

I look forward to the finished patch.

Andrew C

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In article <389DDADB.5AB04519@ibm.net>, cli### [at] ibmnet wrote:

> That is pretty cool! I was just reading about something like that in
> Scientific American magazine...About virtual weathering.  I don't know
> if anyone has brought this up before, but the article is at:
> 
> http://www.sciam.com/2000/0200issue/0200dorsey.html
> 
> I look forward to the finished patch.

I must not have gotten that issue yet...or my parents lost it before I 
could get my hands on it. I will take a look at that site, though...

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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Although I certainly like what you're doing I wanted to ask if this is just
plain impossible as a texture pattern type of thing instead of a kind of media
sampling method which you are apparently trying out here.
It's the scattered look to the partial places that bothers me, if this were to
be considered a patina or similar then a smooth transition zone would probably
be considered best.
As is at least it could be faked well for more distant or smaller objects.

Bob

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In article <389e73ec@news.povray.org>, "Bob Hughes" 
<per### [at] aolcom?subject=PoV-News:> wrote:

> Although I certainly like what you're doing I wanted to ask if this 
> is just plain impossible as a texture pattern type of thing instead 
> of a kind of media sampling method which you are apparently trying 
> out here.

I am not sure what you mean here...this is an ordinary texture, no media 
used. The sampling really has more in common with blurred 
reflection/transparence, it isn't much like media. It shoots rays in a 
hemisphere(so rays are not shot into the object) on the surface of the 
object and returns the percentage of them that hit the object.


> It's the scattered look to the partial places that bothers me, if 
> this were to be considered a patina or similar then a smooth 
> transition zone would probably be considered best. As is at least it 
> could be faked well for more distant or smaller objects.

Using more samples would smooth it out, and there might be ways to use 
the samples other than just calculating the percentage that hit that 
would give smoother results.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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On Sun, 06 Feb 2000 12:42:08 -0500, Chris Huff
<chr### [at] yahoocom> wrote:

>This is my first success with my visibility pattern. It is supposed to 
>be copper or a copper alloy with a patina on it, worn away in exposed 
>areas. The syntax is simple, this is the code that produced this image:

In your code I don't see any limit on the direction the sample rays
are shot. I think it would be useful if one could specify a maximum
angle that the sample rays can form with the plane tangent to the
evaluated point. The minimum should of course be 0 because for all
angles below that the sample rays will hit the surface infinitesimally
close to the evaluated point. And the maximum angle is needed to save
the overhead of taking samples straight up when the greatest slope on
the surface is 1/1000. I hope I explained this well, I will illustrate
it with an image if you want.


Peter Popov
pet### [at] usanet
ICQ: 15002700

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In article <elOfON+7XaP2yN5=Ux51qWrwPoaQ@4ax.com>, Peter Popov 
<pet### [at] usanet> wrote:

> In your code I don't see any limit on the direction the sample rays
> are shot. I think it would be useful if one could specify a maximum
> angle that the sample rays can form with the plane tangent to the
> evaluated point. The minimum should of course be 0 because for all
> angles below that the sample rays will hit the surface infinitesimally
> close to the evaluated point. And the maximum angle is needed to save
> the overhead of taking samples straight up when the greatest slope on
> the surface is 1/1000. I hope I explained this well, I will illustrate
> it with an image if you want.

Yes, I am planning on adding those sort of controls later. This was just 
my first working version...there is actually code for part of it(minimum 
angle) that is currently commented out and a bit incomplete. This will 
probably be the first thing I do when I get back to working on this 
patch(I am currently working on a particle simulator, in C++).

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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I can't really ask the right questions since I don't know how you're doing this,
and trying to explain it to me would perhaps be futile.
All I'm wondering though is if this "texture" were more a pattern type than a
sampling of a surface that it might be more linear I guess would be the term.
I'm just dreaming this up in a way that would mean the texture would follow the
contours of any object like a uv map or something and without the sampling sort
of stuff which obviously is hit and miss to deduce where it goes.
Plain and simple I can't understand the dynamics of your work anyhow, so excuse
me if I go way off track trying to figure it out.  What it causes me to think is
that if a object surface can be found and mimicked in a changed way like this
does do then it just seems then that the texture could follow that surface and
be applied as though a typical patterned texture is with the usual way.
I think I see how you might not be following what I say, it reads to me like
round in circles.

Bob

"Chris Huff" <chr### [at] yahoocom> wrote in message
news:chrishuff_99-876954.16213707022000@news.povray.org...
| In article <389e73ec@news.povray.org>, "Bob Hughes"
| <per### [at] aolcom?subject=PoV-News:> wrote:
|
| > Although I certainly like what you're doing I wanted to ask if this
| > is just plain impossible as a texture pattern type of thing instead
| > of a kind of media sampling method which you are apparently trying
| > out here.
|
| I am not sure what you mean here...this is an ordinary texture, no media
| used. The sampling really has more in common with blurred
| reflection/transparence, it isn't much like media. It shoots rays in a
| hemisphere(so rays are not shot into the object) on the surface of the
| object and returns the percentage of them that hit the object.
|
|
| > It's the scattered look to the partial places that bothers me, if
| > this were to be considered a patina or similar then a smooth
| > transition zone would probably be considered best. As is at least it
| > could be faked well for more distant or smaller objects.
|
| Using more samples would smooth it out, and there might be ways to use
| the samples other than just calculating the percentage that hit that
| would give smoother results.
|
| --
| Chris Huff
| e-mail: chr### [at] yahoocom
| Web page: http://chrishuff.dhs.org/

Post a reply to this message