Hugo wrote:
> First off, let me say that my math education is simple. But seen from a
> logic point of view, intensity of light in real life also depends on
> distance.. And things in real life also has a certain "scale".. So how can
> it be "nonsense" if POV works in the same way?
> 

Simple: if you make a scene with a "correct illumination" and if you
decide to rescale your scene (to double or to half the scale), you'll
have a different render result, unless you compensate for the new scale in
light intensity!
Things in real life has a certain scale indeed. But this affects only
it's shape and texture, and not the illumination.

> 
> That's true, from what I know.. But instead of playing clever in this field,
> I'll give you a link to someone who played a lot with light in POV and knows
> how to get marvellous results:
> 
> http://www.ignorancia.org/lightsys/
> 

That's right! Great hint. Thank you.

> Regards,
> Hugo

Post a reply to this message

Attachments:
Download 'us-ascii' (1 KB)

I forgot to say that I know that the intensity of real
lights depends on distance. What I'm saying is that
Pov calculates light attenuation (function of the
distance) in such a way that makes it difficult to
simulate real lights.

Regards

Val

Post a reply to this message

Attachments:
Download 'us-ascii' (1 KB)

Valdemir Carrara wrote:
>
> 2 - There's something strange in the way that light
>   intensity is calculated.

Just use fade_power 2 and fade_distance <diameter of the source>
or sqrt(area of the source) if using irregular source. Fade distance
links the size of the source to intensity. This produces scale independent
light source. Have a look at cornell.pov in 3.5 radiosity files to see
how it works and produces physically correct results. Compare the
result to http://www.graphics.cornell.edu/online/box/box.jpg

The equation is an empirical approximation for near field axial area
source intensity and is more realistic than 1/d^2 for real, non microscopic
sources. At a distance of 5 times the source diameter both equations are
within 1%. Closer to the source the pov equation is more realistic and
at larger distances the difference is minimal.


_____________
Kari Kivisalo

Post a reply to this message