I just discovered a strange side effect with the 'shadowless' lights.
  Try this:

camera { location -z*5 look_at 0 angle 35 }
light_source { <100,100,-100>,1 }
sphere { 0,1 pigment { rgb <1,0,0> } finish { specular 1 } }

  A regular sphere with a highlight.
  Now apply the keyword 'shadowless' to the light source.
  The highlight disappears!
  This works equal in both pov3.0 and 3.1. It also works if the highlight is
a phong highlight instead of a specular one.
  Is this a bug? Should I report to povray.bugreports?

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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I knew of this already.
To keep any highlights you have to have shadowed lights apparently. You
can still use no_shadow on individual objects instead (oh bother) and
retain the highlights.


Nieminen Mika wrote:
> 
>   I just discovered a strange side effect with the 'shadowless' lights.
>   Try this:
> 
> camera { location -z*5 look_at 0 angle 35 }
> light_source { <100,100,-100>,1 }
> sphere { 0,1 pigment { rgb <1,0,0> } finish { specular 1 } }
> 
>   A regular sphere with a highlight.
>   Now apply the keyword 'shadowless' to the light source.
>   The highlight disappears!
>   This works equal in both pov3.0 and 3.1. It also works if the highlight is
> a phong highlight instead of a specular one.
>   Is this a bug? Should I report to povray.bugreports?
> 
> --
> main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
> *_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/POVring.htm
=Bob

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Bob Hughes <inv### [at] aolcom> wrote:
: I knew of this already.
: To keep any highlights you have to have shadowed lights apparently. You
: can still use no_shadow on individual objects instead (oh bother) and
: retain the highlights.

  The problem arises when you have several light sources illuminating an
object and you want one of those to stop casting shadows (but still causing
highlights), but the other ones must still cast the shadows.
  I got this problem yesterday and found no perfect solution to the problem.
  I think this IS a bug.

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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When I first saw that, I thought it really looked like a bug, but then I
started thinking about why they would do that.  It's obvious it was
intentional, since diffuse still works.  The reason, I think, is because
you might want to use shadowless lights to simulate radiosity. 
Radiosity is typically a diffuse effect, so just having diffuse work
should do a pretty good job.  If hilights worked and you had a bunch of
shadowless fill lights, you'd end up with a bunch of bright spots all
over object, making it appear like they are reflecting light from
several light sources without casting any shadows.

So it's probably not a bug.

-Mike

Nieminen Mika wrote:
> 
>   I just discovered a strange side effect with the 'shadowless' lights.
>   Try this:
> 
> camera { location -z*5 look_at 0 angle 35 }
> light_source { <100,100,-100>,1 }
> sphere { 0,1 pigment { rgb <1,0,0> } finish { specular 1 } }
> 
>   A regular sphere with a highlight.
>   Now apply the keyword 'shadowless' to the light source.
>   The highlight disappears!
>   This works equal in both pov3.0 and 3.1. It also works if the highlight is
> a phong highlight instead of a specular one.
>   Is this a bug? Should I report to povray.bugreports?
> 
> --
> main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
> *_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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Mike <Ama### [at] aolcom> wrote:
: When I first saw that, I thought it really looked like a bug, but then I
: started thinking about why they would do that.  It's obvious it was
: intentional, since diffuse still works.  The reason, I think, is because
: you might want to use shadowless lights to simulate radiosity. 
: Radiosity is typically a diffuse effect, so just having diffuse work
: should do a pretty good job.  If hilights worked and you had a bunch of
: shadowless fill lights, you'd end up with a bunch of bright spots all
: over object, making it appear like they are reflecting light from
: several light sources without casting any shadows.

: So it's probably not a bug.

  Perhaps it's not a bug, but a very big flaw.
  As I said in an earlier article, I found this bug yesterday and found no
way to avoid it. I expressly put the light source for the higlights, but
the shadows produced by this light source were very ugly so I made it
shadowless. And then the highlights were gone. I found no solution to the
problem.
  Making the object shadowless is not the answer since there are other
light sources too, and those should cast shadows normally.

  Perhaps a new 'highlightless' keyword should be better.

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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Nieminen Mika wrote:
> 
> Bob Hughes <inv### [at] aolcom> wrote:
> : I knew of this already.
> : To keep any highlights you have to have shadowed lights apparently. You
> : can still use no_shadow on individual objects instead (oh bother) and
> : retain the highlights.
> 
>   The problem arises when you have several light sources illuminating an
> object and you want one of those to stop casting shadows (but still causing
> highlights), but the other ones must still cast the shadows.
>   I got this problem yesterday and found no perfect solution to the problem.
>   I think this IS a bug.
> 

Not a bug, but a poor choice of keyword to implementation. Internaly,
shadowless
makes the light a fill-light, A softer light without highlights. Imagine
those
lights in an umbrella at a professional photographer. 

The way around this (as long as you don't have too many refletive
surfaces)
is to put a normal light at camera location. (These are normally where i
put 
my fill lights anyways)

-- 
Matthew Corey Brown	xen### [at] mindspringcom
             http://www.xenoarch.com

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Matthew Corey Brown - XenoArch <xen### [at] mindspringcom> wrote:
: The way around this (as long as you don't have too many refletive
: surfaces)
: is to put a normal light at camera location. (These are normally where i
: put 
: my fill lights anyways)

  I didn't understand how this corrects the original problem.

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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