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Jerry Stratton <new### [at] hoboes com> 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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In article <39F### [at] inapginrafr>, Gilles Tran
<tra### [at] inapginrafr> wrote:
>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 ???
In the image that you're seeing, it is a white, empty background. The
problem is that if you look at the shadow cast by the pencil, it
disappears at the edge of the paper, as if the paper were floating in
air. I don't want that to happen, but I also don't want an object
visible in the scene--basically, I want the pencil to cast a shadow on
the document that I'm placing this image in, whether that document is a
web page or the printed page. I want the pencil to cast a shadow in that
empty white area so that the pencil's shadow doesn't look odd when I
actually use this image in my documents.
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:
> In the image that you're seeing, it is a white, empty background.
OK, sorry for being dumb. I had understood that the picture shown was what you
wanted, which didn't make much sense...
The white plane with ambient 0 and high diffuse is the simplest solution for
this problem, then.
Just for the fun, you could also fake it with a height_field in the shape of the
shadow : render an orthographic top view of the scene with a background plane
with all the shadows, then extract the shadow parts of the image and turn them
into thin height fields with a water level just above zero. Then remove the
plane object and replace it with the height fields...
G.
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