> I wasn't having a go at you, honest.

Hehaehae....no worries, I've done far worse anyways :)

> All that the looks_like tag does is create internally a group containing
> the light source and the object it looks like.

Hmm...the way I understand it is that if I were to to do it manually, I would place
the light source directly infront of whatever I am assigning as a light source (we
will say a light bulb). I thought looks_like eliminated the need to do that (so the
object acts as the light, casting light uniformally)? That's the way I thought about
it - correct me if I'm wrong :)

Happy Tracing,

Tim Soderstrom
TigerHawk

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Hi Warp, you recently wrote in moray.win:

>   The difference is left as an excercise.
Can you give me a hint, no time to try this out. If you know, please
tell. I always thought the result was identical.

- Lutz
  email : lut### [at] stmuccom
  Web   : http://www.stmuc.com/moray

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In this one:

light_source
{ <1,1,0>, 1
  looks_like { sphere { 0, .1 pigment { rgb 1 } finish { ambient 1 } } }
}

the sphere is translated by the location of the light source. That is,
this produces a sphere that is located at <1,1,0>.

  In this one:

union
{ light_source { <1,1,0>, 1 }
  sphere { 0, .1 no_shadow pigment { rgb 1 } finish { ambient 1 } }
}

however, the sphere is not translated anywhere (of course), so it produces
a sphere that is located at <0,0,0>.

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

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On Tue, 11 Jul 2000 17:44:51 -0500, TigerHawk wrote...
> > I wasn't having a go at you, honest.
> 
> Hehaehae....no worries, I've done far worse anyways :)

No, it's just that recently I've noticed my postings seeming to be 
incredibly caustic and inflammatory, and I'm not doing it deliberately.  
maybe I'm just having one of those months <sigh>

> > All that the looks_like tag does is create internally a group containing
> > the light source and the object it looks like.
> 
> Hmm...the way I understand it is that if I were to to do it manually, I would place
> the light source directly infront of whatever I am assigning as a light source (we
> will say a light bulb). I thought looks_like eliminated the need to do that (so the
> object acts as the light, casting light uniformally)? That's the way I thought about
> it - correct me if I'm wrong :)

You can create a sphere at <0,0,0> and a point light source at <0,0,0> 
and as long as you set the sphere to no_shadow, the light source will 
apply to the rest of the scene as if the sphere wasn't there.

As far as I understand it, this is all that POV does internally when you 
specify a looks_like.  (Although it creates a group containing the light 
and sphere, which is easy enough to do in Moray :)

In other words, all looks_like does is put a visible, completely 
transparent (can you say oxymoron? :) object around the light source.  
The light source still acts as a point/spot/area light, regardless of how 
big the looks_like object is.

Did that make any sense?  And if not, would somebody else like to try 
explaining it?

Bye for now,
     Jamie.

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Hi Warp, you recently wrote in moray.win:

>   In this one:
> .....
> the sphere is translated by the location of the light source. That is,
> this produces a sphere that is located at <1,1,0>.
> 
>   In this one:
> ....
> however, the sphere is not translated anywhere (of course), so it produces
> a sphere that is located at <0,0,0>.
Aw gee, and I thought it was something internal that I hadn't come
across<g>. This is a non-issue in Moray though, since you can see
where the looks_like object is placed, relative to the light.

I assume then, that 

light_source
{ <1,1,0>, 1
  looks_like { sphere { 0, .1 pigment { rgb 1 } finish { ambient 1 } }
}

... and ....

union
{ light_source { <1,1,0>, 1 }
  sphere { 
    0, .1 no_shadow pigment { rgb 1 } finish { ambient 1 } 
    translate <1,1,0>
  }
}

will light scene in the same way, right?

- Lutz
  email : lut### [at] stmuccom
  Web   : http://www.stmuc.com/moray

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Lutz Kretzschmar <lut### [at] stmuccom> wrote:
: I assume then, that 

: light_source
: { <1,1,0>, 1
:   looks_like { sphere { 0, .1 pigment { rgb 1 } finish { ambient 1 } }
: }

: ... and ....

: union
: { light_source { <1,1,0>, 1 }
:   sphere { 
:     0, .1 no_shadow pigment { rgb 1 } finish { ambient 1 } 
:     translate <1,1,0>
:   }
: }

: will light scene in the same way, right?

  Yes, I think so.

  My intention was not to say "these two things are completely different so
moray should support both". They are not completely different, but they differ
only in minor details.
  I was just being picky because you said that they do the same thing so I
had to show that they are not exactly the same thing.
  Anyways, never mind :)

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

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> In other words, all looks_like does is put a visible, completely
> transparent (can you say oxymoron? :) object around the light source.
> The light source still acts as a point/spot/area light, regardless of how
> big the looks_like object is.
>
> Did that make any sense?  And if not, would somebody else like to try
> explaining it?

Yes, that makes perfect sense - I had not realized the mechanics of such an idea would
work - I thought no_shadow simply ment that the object doesn't cast a shadow on the
ground
- it hadn't occoured to me that that would affect other things as well (and that was
pretty dumb, I suppose :)

Thanks for clarifying that for me!

Tim Soderstrom
PsiTron / TigerHawk

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