Is there any way to use "no_image" with an object but still have it 
*accept* (not cast) shadows? Or is there some other way for an object to 
basically be invisible except for the shadows cast on it?

Basically I want to be able to have the background color show through, 
but have 'drop shadows' from objects, for use on web pages and in 
documents.

Jerry
http://www.hoboes.com/jerry/

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Jerry Stratton wrote in message ...
>Is there any way to use "no_image" with an object but still have it
>*accept* (not cast) shadows? Or is there some other way for an object to
>basically be invisible except for the shadows cast on it?


Try making a plane that is perpendicular to the camera, then give it your
background color, an ambient of 0, and a diffuse of 1000 or so.  This will
give a plane that is your background color over its entire surface except
for where it is shadowed, where it will be completely black.  If you need to
add transparency to the resulting image, add it in an external program.

Mark

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Jerry Stratton <new### [at] hoboescom> wrote:
: Is there any way to use "no_image" with an object but still have it 
: *accept* (not cast) shadows? Or is there some other way for an object to 
: basically be invisible except for the shadows cast on it?

  There's no logical interpretation to this.
  A shadow is a modification in the illumination of the surface. A shadow
causes a dimmer lighting in some part of the surface.
  However, if the surface is invisible, it doesn't have lighting at all.
How can you modify an inexistent lighting?

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

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I think you can pull this off by making your object and giving it a bounding
box around the lightsource.
You have to tell POV-Ray not to ignore bounded-by.

Josh

Jerry Stratton wrote:

> Is there any way to use "no_image" with an object but still have it
> *accept* (not cast) shadows? Or is there some other way for an object to
> basically be invisible except for the shadows cast on it?
>
> Basically I want to be able to have the background color show through,
> but have 'drop shadows' from objects, for use on web pages and in
> documents.
>
> Jerry
> http://www.hoboes.com/jerry/

--
Josh English -- Lexiphanic Lethomaniac
eng### [at] spiritonecom
The POV-Ray Cyclopedia http://www.spiritone.com/~english/cyclopedia/

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In article <39F84C07.FBCD12E4@spiritone.com>, Josh English 
<eng### [at] spiritonecom> wrote:

> I think you can pull this off by making your object and giving it a 
> bounding box around the lightsource.

That will make it *cast* shadows, but it still won't "accept" shadows, 
whatever that would mean...there has to be something visible for the 
shadows to appear on.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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Jerry Stratton wrote:

> Is there any way to use "no_image" with an object but still have it
> *accept* (not cast) shadows? Or is there some other way for an object to
> basically be invisible except for the shadows cast on it?
> Basically I want to be able to have the background color show through,
> but have 'drop shadows' from objects, for use on web pages and in
> documents.

Do you mean that if a particular intersection point on the object is in
shadow (another object between it and any light source) then that
intersection point __is__ counted as an intersection point but if it is not
in shadow it isn't?
Interesting idea!
--
Bye
Pabs

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With this definition, he could do CSG with the object and a cone/prism
representing the light source.

Pabs wrote:

> Jerry Stratton wrote:
>
> > Is there any way to use "no_image" with an object but still have it
> > *accept* (not cast) shadows? Or is there some other way for an object to
> > basically be invisible except for the shadows cast on it?
> > Basically I want to be able to have the background color show through,
> > but have 'drop shadows' from objects, for use on web pages and in
> > documents.
>
> Do you mean that if a particular intersection point on the object is in
> shadow (another object between it and any light source) then that
> intersection point __is__ counted as an intersection point but if it is not
> in shadow it isn't?
> Interesting idea!
> --
> Bye
> Pabs

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ah. That will teach me to read a bit more....

Josh

Chris Huff wrote:

> In article <39F84C07.FBCD12E4@spiritone.com>, Josh English
> <eng### [at] spiritonecom> wrote:
>
> > I think you can pull this off by making your object and giving it a
> > bounding box around the lightsource.
>
> That will make it *cast* shadows, but it still won't "accept" shadows,
> whatever that would mean...there has to be something visible for the
> shadows to appear on.
>
> --
> Christopher James Huff
> Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
> TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
>
> <><

--
Josh English -- Lexiphanic Lethomaniac
eng### [at] spiritonecom
The POV-Ray Cyclopedia http://www.spiritone.com/~english/cyclopedia/

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In article <39F8E5BB.635DE760@hotmail.com>, Pabs <pab### [at] hotmailcom> 
wrote:
>Jerry Stratton wrote:
>> Is there any way to use "no_image" with an object but still have it
>> *accept* (not cast) shadows? Or is there some other way for an object to
>> basically be invisible except for the shadows cast on it?
>> Basically I want to be able to have the background color show through,
>> but have 'drop shadows' from objects, for use on web pages and in
>> documents.
>
>Do you mean that if a particular intersection point on the object is in
>shadow (another object between it and any light source) then that
>intersection point __is__ counted as an intersection point but if it is not
>in shadow it isn't?

I think that's what I mean. In any case, Mark's idea of making a plane 
with diffuse 1000 and the same color as the background worked for me 
(although as Mark said, if I'd wanted transparency it wouldn't have; 
fortunately, I didn't).

You can see an example of why I wanted it at 
http://www.hoboes.com/html/RPG/The%20Game/The%20Game00.jpg

or go to

http://www.hoboes.com/html/RPG/The%20Game/

and click on the PDF link or either of the two HTML links.

The pencil casts a shadow on the paper, and the shadow abruptly 
disappears when the paper ends because there is no object to "accept" a 
shadow outside of the paper. I don't want another object there... but I 
do want the pencil to cast a shadow (and the dice also, theoretically, 
but their shadows are hidden by themselves).

A plane of diffuse 1000, ambient the same as the paper seems to work 
great (it was after midnight when I got around to trying it last night, 
and I didn't want to upload without paying more attention to the image).

(Notice that there's also what appears to be a stray shadow in the scene 
coming off of "telepathic". I have no idea where that's coming from. 
There's only one light source in the scene. But where it might be 
considered a stray mark on the paper, when I put the plane in, the 
shadow hits the plane as well so I'm going to have to fix it.)

Jerry
-- 
http://www.hoboes.com/jerry/
"Give a man a fish and you feed him for a day. Teach him to fish, and you've
depleted the lake."--It Isn't Murder If They're Yankees
(http://www.hoboes.com/jerry/Murder/)

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Jerry wrote:

> You can see an example of why I wanted it at
> http://www.hoboes.com/html/RPG/The%20Game/The%20Game00.jpg

Forgive me if I'm missing something obvious here, but why not just use a white,
empty background behind the paper ???
G.

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