Hi, people.

I already posted this in povray.programming, but they told me to post it
here

I'd like to produce some kind of street lamp, but it has some special kind
of glass (somebody said 'ground glass', but I'm still not sure, if it's the
right name), I can't produce...
You should not be able to look through it, it should have a white color, and
it should let the light through. And if there's light on the other side of
the glass shining in the camera's direction, it should be visible on the
glass....
(This glass is used in these detective-films, for example; maybe you know
these office-doors with the white glass and the black text on it....)

Please help me

Thanks in advance
Wolfgang

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On Tue, 25 Apr 2000 21:30:49 +0200, Wolfgang Illmeyer wrote:
>
>I'd like to produce some kind of street lamp, but it has some special kind
>of glass (somebody said 'ground glass', but I'm still not sure, if it's the
>right name), I can't produce...

'round here, we call that frosted glass.  It's not that easy to get right
in POV, but you can fake it with either media (tricky, and prone to failure)
or a very small normal pattern with heavy nonadaptive antialiasing.  Your
render times will go through the roof, though.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
These are my opinions.  I do NOT speak for the POV-Team.

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"Ron Parker" <ron### [at] povrayorg> wrote in message
news:slr### [at] linuxparkerrfwicom...
| On Tue, 25 Apr 2000 21:30:49 +0200, Wolfgang Illmeyer wrote:
| >
| >I'd like to produce some kind of street lamp, but it has some special kind
| >of glass (somebody said 'ground glass', but I'm still not sure, if it's the
| >right name), I can't produce...
|
| 'round here, we call that frosted glass.  It's not that easy to get right
| in POV, but you can fake it with either media (tricky, and prone to failure)
| or a very small normal pattern with heavy nonadaptive antialiasing.

Using a low enough filter value along with a little transmit can do okay along with
the normal (I almost always use granite for that) so long as the pigment color is
white
enough.  Can even go over rgb 1 as in rgbft <1.5,1.5,1.5,0.25,0.125> for example.
Then of course for the normal to do it's stuff you need a ior and specular highlight.
You'll certainly find that things will change dramatically when the camera and/or
light are moved. So it can often be a case of adjusting for one viewpoint.

Bob

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In article <39062a35@news.povray.org>, "Bob Hughes" 
<per### [at] aolcom?subject=PoV-News:> wrote:

> Using a low enough filter value along with a little transmit can do 
> okay along with the normal (I almost always use granite for that) so 
> long as the pigment color is white enough.  Can even go over rgb 1 as 
> in rgbft <1.5,1.5,1.5,0.25,0.125> for example. Then of course for the 
> normal to do it's stuff you need a ior and specular highlight. You'll 
> certainly find that things will change dramatically when the camera 
> and/or light are moved. So it can often be a case of adjusting for 
> one viewpoint.

I did this a while ago, I posted some images to povray.binaries.images. 
While I used a blurred transparency patch, the same thing could be done 
with finely scaled normals.
I used a white pigment with about half transparency, ambient 0, some 
reflection, and a diffuse value which added up with reflection to equal 
1.(I usually try to design my textures so diffuse+ambient+reflection <= 
1) I also added double_illuminate, so the glass is lit on both sides.(of 
course, the last one requires MegaPOV)

Media should also work, I don't see why it would be "prone to failure". 
It could be hard to adjust though...and probably slower than any other 
option(unless you use MegaPOV and media method 2 or 3).

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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Chris Huff wrote:

> Media should also work, I don't see why it would be "prone to failure".
> It could be hard to adjust though...and probably slower than any other
> option(unless you use MegaPOV and media method 2 or 3).

Using media densities is really not that slow in the official version.
It's when you use scattering media that things slow way down.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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In article <39062EF7.1EFF9133@pacbell.net>, lin### [at] povrayorg 
wrote:

> Using media densities is really not that slow in the official version.
> It's when you use scattering media that things slow way down.

You would have to use scattering media to get ground or frosted glass to 
work right. Emitting media might fake it under some special conditions, 
but it would be limited, and I think absorbing media would be useless 
for this.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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You can get the effect with scattering media in the lamp shade. It does require
a bit of tweaking, though. The render time will be somewhat high if you desire
smooth results. Alternatively you might want to try using MegaPOV, which has a
different method for rendering media. It will give smooth results at lower
settings and thus render faster.
I'll post an example scene to povray.binaries.scene-files; perhaps you can use
it as a basis.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg

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erm... and what does this mean? Could you show me some scene-code?

Ron Parker <ron### [at] povrayorg> schrieb in im Newsbeitrag:
slr### [at] linuxparkerrfwicom...
> On Tue, 25 Apr 2000 21:30:49 +0200, Wolfgang Illmeyer wrote:
> >
> >I'd like to produce some kind of street lamp, but it has some special
kind
> >of glass (somebody said 'ground glass', but I'm still not sure, if it's
the
> >right name), I can't produce...
>
> 'round here, we call that frosted glass.  It's not that easy to get right
> in POV, but you can fake it with either media (tricky, and prone to
failure)
> or a very small normal pattern with heavy nonadaptive antialiasing.  Your
> render times will go through the roof, though.
>
> --
> Ron Parker   http://www2.fwi.com/~parkerr/traces.html
> These are my opinions.  I do NOT speak for the POV-Team.
>

Post a reply to this message

Chris Huff <chr### [at] yahoocom> schrieb in im Newsbeitrag:
chrishuff_99-16FADB.18455525042000@news.povray.org...
> In article <39062a35@news.povray.org>, "Bob Hughes"
> <per### [at] aolcom?subject=PoV-News:> wrote:
>
> I did this a while ago, I posted some images to povray.binaries.images.

I'm sorry, I can't find this, because my newsreader-program crashes after
about 3000 messages ;)

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Something like this perhaps might do okay.

box {-1,1 scale <4,3,.1>
 texture {
  pigment { rgbft <1.5,1.5,1.5,.25,.125>}
   normal {granite .15 scale .005}
    finish {ambient .05 diffuse .5 specular .8 roughness .01 reflection .15}
  scale 2 // scale texture to suit object/scene size
 }
  interior {ior 1.5 caustics 1}
}

sphere {<0,0,1.5>,1 pigment {color red 1}}

light_source { <-.5,1.25,-1.5> color rgb <1,.95,.9>
}
camera {
  location  <1,.75,-2>
  angle 65
  look_at   <0, 0, 0>
}


Bob

"Wolfgang Illmeyer" <wol### [at] gmxnet> wrote in message
news:3906dbe7@news.povray.org...
| erm... and what does this mean? Could you show me some scene-code?
|
| Ron Parker <ron### [at] povrayorg> schrieb in im Newsbeitrag:
| slr### [at] linuxparkerrfwicom...
| > On Tue, 25 Apr 2000 21:30:49 +0200, Wolfgang Illmeyer wrote:
| > >
| > >I'd like to produce some kind of street lamp, but it has some special
| kind
| > >of glass (somebody said 'ground glass', but I'm still not sure, if it's
| the
| > >right name), I can't produce...
| >
| > 'round here, we call that frosted glass.  It's not that easy to get right
| > in POV, but you can fake it with either media (tricky, and prone to
| failure)
| > or a very small normal pattern with heavy nonadaptive antialiasing.  Your
| > render times will go through the roof, though.
| >
| > --
| > Ron Parker   http://www2.fwi.com/~parkerr/traces.html
| > These are my opinions.  I do NOT speak for the POV-Team.
| >
|

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