Using a filter? Please elaborate. I'd like to know how you do this.

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Richard Speir wrote:
> 
> Using a filter? Please elaborate. I'd like to know how you do this.

A simple way would be to use something like a box in front of the camera
with a filtering pigment. Only certain colors owuld be allowed to pass
while others would be blocked. If you use several layers of pigments
you can greatly lower the bands of permissable colors allowed to pass.

I'm not sure if this is what he had in mind but it will work to some extent.

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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Ken <tyl### [at] pacbellnet> wrote:
: Anyway My solutions was of course to use shades of gray for all objects
: in the scene.

  How do you model this:

  Three objects: One is yellow, one is cyan and one is white.
  Two light sources: One is red and the other is blue.
  Of course the red light source only illuminates the yellow and the white
object while the blue light source only illuminates the cyan and also
the white object.
  I want this image in b/w.

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

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Nieminen Mika wrote:
> 
> Ken <tyl### [at] pacbellnet> wrote:
> : Anyway My solutions was of course to use shades of gray for all objects
> : in the scene.
> 
>   How do you model this:
> 
>   Three objects: One is yellow, one is cyan and one is white.
>   Two light sources: One is red and the other is blue.
>   Of course the red light source only illuminates the yellow and the white
> object while the blue light source only illuminates the cyan and also
> the white object.
>   I want this image in b/w.
> 
> --
> main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
> ):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

If you really want this so badly I suggest...

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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Nieminen Mika <war### [at] cctutfi> writes:

>   How do you model this:
> 
>   Three objects: One is yellow, one is cyan and one is white.
>   Two light sources: One is red and the other is blue.
>   Of course the red light source only illuminates the yellow and the white
> object while the blue light source only illuminates the cyan and also
> the white object.
>   I want this image in b/w.

I wondered how long it would take until someone would notice this...
I'm afraid you all lost :-)

The doc says it all (almost):

--- Cut here ---
7.8.4            HF_Gray_16

The hf_gray_16 setting is useful when using POV-Ray to generate
heightfields for use in other POV-Ray scenes. The syntax is...

  global_settings { hf_gray_16 BOOLEAN }


The boolean value turns the option on or off. If the keyword is
specified without the boolean value then the option is turned on. If
hf_gray_16 is not specified in any global_settings statement in the
entire scene then the default is off.

When hf_gray_16 is on, the output file will be in the form of a
heightfield, with the height at any point being dependent on the
brightness of the pixel.  The brightness of a pixel is calculated in
the same way that color images are converted to grayscale images:

  height = 0.3 * red + 0.59 * green + 0.11 * blue


Setting the hf_gray_16 option will cause the preview display, if used,
to be grayscale rather than color. This is to allow you to see how the
heightfield will look because some file formats store heightfields in
a way that is difficult to understand afterwards. See section "Height
Field" for a description of how POV-Ray heightfields are stored for
each file type.
--- Cut here ---

Maybe it should have been a bit clearer.  Anyway, the output is (at
least in Targa Truevision format) a sixteen bit per pixel black and
white image file.

Roland.
-- 
Roland Mas


- Genki desu, ture en zinc.

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Nieminen Mika <war### [at] cctutfi> writes:

>   How do you model this:
> 
>   Three objects: One is yellow, one is cyan and one is white.
>   Two light sources: One is red and the other is blue.
>   Of course the red light source only illuminates the yellow and the white
> object while the blue light source only illuminates the cyan and also
> the white object.
>   I want this image in b/w.

I wondered how long it would take until someone would notice this...
I'm afraid you all lost :-)

The doc says it all (almost):

--- Cut here ---
7.8.4            HF_Gray_16

The hf_gray_16 setting is useful when using POV-Ray to generate
heightfields for use in other POV-Ray scenes. The syntax is...

  global_settings { hf_gray_16 BOOLEAN }


The boolean value turns the option on or off. If the keyword is
specified without the boolean value then the option is turned on. If
hf_gray_16 is not specified in any global_settings statement in the
entire scene then the default is off.

When hf_gray_16 is on, the output file will be in the form of a
heightfield, with the height at any point being dependent on the
brightness of the pixel.  The brightness of a pixel is calculated in
the same way that color images are converted to grayscale images:

  height = 0.3 * red + 0.59 * green + 0.11 * blue


Setting the hf_gray_16 option will cause the preview display, if used,
to be grayscale rather than color. This is to allow you to see how the
heightfield will look because some file formats store heightfields in
a way that is difficult to understand afterwards. See section "Height
Field" for a description of how POV-Ray heightfields are stored for
each file type.
--- Cut here ---

Maybe it should have been a bit clearer.  Anyway, the output can be
turned into a sixteen bit per pixel black and white image file.  I
first wrote "at least in Truevision format", but it is not true.  My
further tests reveal that it works with "PNG" format.  Hence my
superseding of my previous article.

Roland.
-- 
Roland Mas


- Genki desu, ture en zinc.

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One method would be to use the hue and intensity values of the color to
form the grey scale value of that color, and then render the grey scale
colors.  Perhaps applying a greyscale equation to your pigments?

Steve


Nieminen Mika wrote:
> 
> Ken <tyl### [at] pacbellnet> wrote:
> : Anyway My solutions was of course to use shades of gray for all objects
> : in the scene.
> 
>   How do you model this:
> 
>   Three objects: One is yellow, one is cyan and one is white.
>   Two light sources: One is red and the other is blue.
>   Of course the red light source only illuminates the yellow and the white
> object while the blue light source only illuminates the cyan and also
> the white object.
>   I want this image in b/w.
> 
> --
> main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
> ):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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Lance Birch wrote in message <36e8a932.0@news.povray.org>...
>The best way is to convert all the colours in your scene to shades of gray
>using a grayscale algorithm.  You can't currently tell POV-Ray to render to
>greyscale.


Sure you can!
Check out the global-settings option "HF_Gray_16" (it has it's own little
chapter in the docs BTW).



Johannes.

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So it goes...

My answer lingered a bit in the outbox, and when I looked the next time,
Roland had already given the correct answer :-)  - by then my answer was
already posted ...

Johannes.

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Didn't somebody post a POV ray file that converted from RGB to HSB and HSV...
those would probably be most helpful in created a B&W image.


Stephen Lavedas wrote:

> One method would be to use the hue and intensity values of the color to
> form the grey scale value of that color, and then render the grey scale
> colors.  Perhaps applying a greyscale equation to your pigments?
>
> Steve
>
> Nieminen Mika wrote:
> >
> > Ken <tyl### [at] pacbellnet> wrote:
> > : Anyway My solutions was of course to use shades of gray for all objects
> > : in the scene.
> >
> >   How do you model this:
> >
> >   Three objects: One is yellow, one is cyan and one is white.
> >   Two light sources: One is red and the other is blue.
> >   Of course the red light source only illuminates the yellow and the white
> > object while the blue light source only illuminates the cyan and also
> > the white object.
> >   I want this image in b/w.
> >
> > --
> > main(i,_){for(_?main(i+1,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[--i]
> > ):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

--
Josh English
eng### [at] spiritonecom
www.spiritone.com/~english

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