Lights visibility with Directionality higher than 0,5

[alessandro deana]

I everybody,
I already post this issue on "need help" category, but according with the answers, I think this could be a bug.
Feel free to cancel the other post: https://forum.corona-renderer.com/index.php/topic,6539.0.html

The more I increase the value of the Directionality, the more light looks darker in direct visibility.
If I use values under 0,5 the lights looks good, but if I set this value higher than 5,5 the light looks black.

Pokoy said the behavior makes sense since light rays are focused and you can't 'see' them when you are outside of the light beam, but I think this is not the behaviour in real word.

These are some examples:
01 - directionality 0
02 - directionality 0,5
03 - directionality 0,55
04 - the result I need

What do you think about it?

[borisquezadaa]

Actualy is real life behavior of a ligth source. What you see are interreflections in a glass that ligth goes through or an incandesent metal or even both. But in case of a CG ligth there is none of those.
Best way to do is to apply a ligth material to a disk IMHO.

[romullus]

Correct me if i wrong, but AFAIK there's no such thing as light's directionality in RL - photons are emiting in all directions equally.

p.s. maybe we should do a list of common "bugs" in Corona and stick it at the top of this section, so people stop falsely reporting it over and over again?

[Ondra]

Correct me if i wrong, but AFAIK there's no such thing as light's directionality in RL - photons are emiting in all directions equally.

If light directionality does not exist, then IES lights also do not exist. Lets not involve physics into this - lights in CG scenes are simplifications of reality - you really do not want to render with lightbulb filament modelled. That is why we have simplifications such as IES profiles and light directionality.

[romullus]

Don't get me wrong, it wasn't my intention to debate about necessity of various hacks in Corona. It was merely a reply to a statement that light is acting the same way in RL, nothing more.

[FrostKiwi]

I came across the same issue. It's how directionality is supposed to work, there is a workaround however:
Use a Blend mat to apply a selfillumination map to the area of the light.
If the camera is in the Lightcone, it will show as usual, if you are outside of it, the selfillumination map will fake the reflecting glass, like in reallife.
pic related :]

[Ondra]

between this and the other thread, I hope it was sufficiently explained that this is not a bug