I needed to demonstrate the difference in diffuse and specular illumination
caused by the area_light of POV-Ray (which simply uses a point light for
those) compared to a true grid of pointlights with a simple scene.
  Even though simple, the result was so nice that I decided to post it here.

  The first image uses just an area_light. The second image creates a
grid of pointlights equivalent to the area_light (ie same amount of
points). The second image was, naturally, several times slower to
render.

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Attachments:
Download 'arealight.jpg' (29 KB) Download 'lightgrid.jpg' (28 KB)

Preview of image 'arealight.jpg'

Preview of image 'lightgrid.jpg'

> The second image was, naturally, several times slower to
> render.


It would be possible, and perhaps convenient for some, to add a keyword to
the area light which causes it to behave like a grid of lights for diffuse
and specular lighting effects. The only advantage of this over an actual
grid of lights is that not every light has to be sampled for shadows (the
adaptive sampling can be used), but this is a significant advantage.

 - Slime
 [ http://www.slimeland.com/ ]

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Slime <fak### [at] emailaddress> wrote:
> It would be possible, and perhaps convenient for some, to add a keyword to
> the area light which causes it to behave like a grid of lights for diffuse
> and specular lighting effects. The only advantage of this over an actual
> grid of lights is that not every light has to be sampled for shadows (the
> adaptive sampling can be used), but this is a significant advantage.

  Actually I came up with this exact same idea. It shouldn't be too
difficult to implement either.

-- 

                                                          - Warp

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The desktop reflection, or rather highlighting, of the light object might be 
the most dramatic change of all. Seems to be a slight change in the shadow 
at the base, too, although I don't notice any difference in the sphere's 
shadow.

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Bob Hughes wrote:
> The desktop reflection, or rather highlighting, of the light object might be 
> the most dramatic change of all. Seems to be a slight change in the shadow 
> at the base, too, although I don't notice any difference in the sphere's 
> shadow.
> 
> 
Interesting.
I let gimp calculate the difference image
(pixel that differ are bright).
As you said the shadow isn't affected (as expected).
The image is desaturated and contrast is a bit enhanced.

Sebastian

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Attachments:
Download 'diff.jpg' (24 KB)

Preview of image 'diff.jpg'

"Sebastian H." <van### [at] gmxde> wrote in message 
news:42ef4cb6@news.povray.org...
> Bob Hughes wrote:
>> The desktop reflection, or rather highlighting, of the light object might 
>> be
>> the most dramatic change of all. Seems to be a slight change in the 
>> shadow
>> at the base, too, although I don't notice any difference in the sphere's
>> shadow.
>>
>>
> Interesting.
> I let gimp calculate the difference image
> (pixel that differ are bright).
> As you said the shadow isn't affected (as expected).

Looks like the light spread, or diffusion, on the desktop nearest the source 
is quite different-- if I read this image right (darker least changed, 
lighter most changed). Maybe that's why I thought the shadow there might be 
different. I like how this shows zones of no change between the rest of it, 
showing as rings of blackness.

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Bob Hughes wrote:
> "Sebastian H." <van### [at] gmxde> wrote in message 
> news:42ef4cb6@news.povray.org...
> 
>>Bob Hughes wrote:
>>
>>>The desktop reflection, or rather highlighting, of the light object might 
>>>be
>>>the most dramatic change of all. Seems to be a slight change in the 
>>>shadow
>>>at the base, too, although I don't notice any difference in the sphere's
>>>shadow.
>>>
>>>
>>
>>Interesting.
>>I let gimp calculate the difference image
>>(pixel that differ are bright).
>>As you said the shadow isn't affected (as expected).
> 
> 
> Looks like the light spread, or diffusion, on the desktop nearest the source 
> is quite different-- if I read this image right (darker least changed, 
> lighter most changed).

Right. There is a greater color difference between the two images
in bright areas.

> Maybe that's why I thought the shadow there might be 
> different. I like how this shows zones of no change between the rest of it, 
> showing as rings of blackness.

Yeah, interesting indeed.
I like (if this is of value in this image at all)
the bright ring behing the light source.
It shows that the outer areas are be much brighter with multiple
light sources whereas the center color does not differ much.
Probably because of the colormodel used in the image (24bit rgb).
The center color cannot have more brightness than maximum brightness in 
rgb model.

Sebastian

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