Hello out there!

My problem: shadowless lights and polished surfaces don't work together

I'm sure I already read about this some years ago when I started using
PovRay in v2.x. However, I just encountered the phenomen again. When you
define a scene and use the shadowless keyword to prevent the light
source from casting shadows this lightsource will not highlight an
object with a highlighting surface finish as e.g. phong. Is it a bug or
a feature? I don't know but since shadowless lights are originally meant
to "fill up" the light in the scene it might be a feature.

I'm using shadowless lights because I want to render a complex scene
representing a crystall lattice with some 10000 atoms in it. Not using
shadowless lights inevitabily leads to the inner atoms being always in
the shadow of the outer ones. 
However - even if it is not at all scientific but perhaps artistic - I
might like to have polished surfaces with small highlights. 

Is there anyone who knows a trick to solve this problem except for using
one lightsource for every atom???

You can see an example of what I'm rendering at
http://www.geocities.com/SiliconValley/Lakes/5432/test/sic.jpg

Uwe.

-------------------------------------------------
Uwe Zimmermann                uwe### [at] geocitiescom	
Dipl. Phys.                     uwe### [at] elekthse 

           Department of Electronics
            Solid State Electronics
         Royal Institute of Technology
                 Electrum 229
           S-16440 Kista-Stockholm
                   Sweden

http://www.ele.kth.se/FTE/personal/pers_uwe.html
------------------------------------------------

Post a reply to this message

On Wed, 23 Jun 1999 19:34:52 +0200, Uwe Zimmermann wrote:
>Is there anyone who knows a trick to solve this problem except for using
>one lightsource for every atom???

I think you can bound it with a small sphere around the camera
to get this effect, as long as you don't care whether it shows
up in reflections, and as long as it doesn't have any transparent
parts.  The result will be that only rays that hit the bounding
surface will be allowed to hit the object, so the only rays that
will hit the object will be camera rays.  In particular, shadow
rays (and transmitted rays and reflected rays) won't be tested
against that object.

camera { location Camera_Location look_at Object_Center }
object { My_Object
         bounded_by { sphere { Camera_Location, .01 } }
       }

Post a reply to this message

It is also possible to add the no_shadow keyword to the objects, that should
do the trick too !

greetings Lars

> Hello out there!
>
> My problem: shadowless lights and polished surfaces don't work together
>
> I'm sure I already read about this some years ago when I started using
> PovRay in v2.x. However, I just encountered the phenomen again. When you
> define a scene and use the shadowless keyword to prevent the light
> source from casting shadows this lightsource will not highlight an
> object with a highlighting surface finish as e.g. phong. Is it a bug or
> a feature? I don't know but since shadowless lights are originally meant
> to "fill up" the light in the scene it might be a feature.
>
> I'm using shadowless lights because I want to render a complex scene
> representing a crystall lattice with some 10000 atoms in it. Not using
> shadowless lights inevitabily leads to the inner atoms being always in
> the shadow of the outer ones.
> However - even if it is not at all scientific but perhaps artistic - I
> might like to have polished surfaces with small highlights.
>
> Is there anyone who knows a trick to solve this problem except for using
> one lightsource for every atom???
>
> You can see an example of what I'm rendering at
> http://www.geocities.com/SiliconValley/Lakes/5432/test/sic.jpg
>
> Uwe.
>
> -------------------------------------------------
> Uwe Zimmermann                uwe### [at] geocitiescom
> Dipl. Phys.                     uwe### [at] elekthse
>
>            Department of Electronics
>             Solid State Electronics
>          Royal Institute of Technology
>                  Electrum 229
>            S-16440 Kista-Stockholm
>                    Sweden
>
> http://www.ele.kth.se/FTE/personal/pers_uwe.html
> ------------------------------------------------

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I found it - again,

and I appologize for me bothering you with such a stupid question. Of
course you have to use the no_shadow option of the objects - stupid
me!!!

But: you won't find this easily by simply browsing the help
file/documentation...


Uwe.

Post a reply to this message

Uwe Zimmermann wrote in message <37711ABC.F7A20B15@ele.kth.se>...
>Is there anyone who knows a trick to solve this problem except for using
>one lightsource for every atom???
>


Remove shadowless from the lights and add no_shadow to all the objects.

Might work.

Gail
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