> I think you are right...area lights only affect shadows, the shading is
> the same as for point lights.

is this true?  i thought area lights were made of several point lights. 
if what you are saying is true, than if my area light is bigger than my
object (a sphere for example) the light side is only one hemisphere
instead of more than a hemisphere?  that seems wrong to me.  take the
following sketches for further example:

0----0----0----0<---area light           0 <--point light
        0<-sphere                        0<-sphere

in example one it seems to me that light from the outer edges of the
area light should get farther underneath the point light than in example
two.  example two should light less than one hemisphere and example one
should light way more than a hemisphere.  in my opinion, if this isn't
how it works, it's wrong and should be fixed.

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On Thu, 03 Aug 2000 13:35:30 -0700, ryan constantine wrote:
>in example one it seems to me that light from the outer edges of the
>area light should get farther underneath the point light than in example
>two.  example two should light less than one hemisphere and example one
>should light way more than a hemisphere.  in my opinion, if this isn't
>how it works, it's wrong and should be fixed.

That's not how it works.  That's even not how it's documented to work:

|  The area_light keyword in POV-Ray creates sources that are rectangular 
|  in shape, sort of like a flat panel light. Rather than performing the 
|  complex calculations that would be required to model a true area light, 
|  it is approximated as an array of point light sources spread out over 
|  the area occupied by the light. The array-effect applies to shadows only. 
|  The object's illumination is still that of a point source. The intensity 
|  of each individual point light in the array is dimmed so that the total 
|  amount of light emitted by the light is equal to the light color specified 
|  in the declaration. 

If you want "real" area lights, use an array of point lights.  Be aware that 
that will make your render time a lot slower; so would "fixing" the current
implementation.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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> That's not how it works.  That's even not how it's documented to work:

so that should mean there are self shadow errors because parts that
would be lit be a real area light aren't lit and can't cast shadows
right?  and what about parts that aren't lit that would contribute to a
cast shadow on another object?  i've read the docs over and over, but
you know you always catch something new each time, and i just hadn't
caught what you quoted to me.  thanks.  i still wish it worked right. 
i'll have to keep point arrays in mind for the future.

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ryan constantine wrote:

> i still wish it worked right.

It works exactly how it was designed to work.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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On Fri, 04 Aug 2000 00:22:22 -0700, ryan constantine wrote:
>
>> That's not how it works.  That's even not how it's documented to work:
>
>so that should mean there are self shadow errors because parts that
>would be lit be a real area light aren't lit and can't cast shadows
>right?  and what about parts that aren't lit that would contribute to a
>cast shadow on another object? 

Neither of those is a concern.  Shadows work correctly.  They're designed to.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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that's good to know and i appreciate all of the insight.

Ron Parker wrote:
> 
> On Fri, 04 Aug 2000 00:22:22 -0700, ryan constantine wrote:
> >
> >> That's not how it works.  That's even not how it's documented to work:
> >
> >so that should mean there are self shadow errors because parts that
> >would be lit be a real area light aren't lit and can't cast shadows
> >right?  and what about parts that aren't lit that would contribute to a
> >cast shadow on another object?
> 
> Neither of those is a concern.  Shadows work correctly.  They're designed to.
> 
> --
> Ron Parker   http://www2.fwi.com/~parkerr/traces.html
> My opinions.  Mine.  Not anyone else's.

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More importantly, ask yourself the question: Is it partially shaded or
partially lit?  Just so happens that both are true, so there's no point
in calculating both.

Only thing that is missed are 100% accurate soft highlights, but
highlights are faked anyway so that's a moot point. :D

-Mike

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