Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] General Discussion => Topic started by: dsolod on 2021-03-26, 07:16:00

Title: Spot light beam angle and CoronaLight Directionality
Post by: dsolod on 2021-03-26, 07:16:00

Hello,
Is it the linear dependence between the technical characteristic of the light source and CoronaLight parameter? Let's say setting the Directionality to 0,5 will be physically correct for 90 degrees beam angle?
Thanks

Dmitry

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: maru on 2021-03-26, 17:34:31

Not sure if I understand your question correctly, but I would say that directionality 1 = 90 degrees beam (the light shoots straight from the light object's normals - like laser).

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: burnin on 2021-03-26, 18:02:55

Area light directionality % with Corona 7daily for C4D
@ 1 fps
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=32800.0;attach=145055;image)

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: dsolod on 2021-03-27, 05:48:58

Quote from: maru on 2021-03-26, 17:34:31

Not sure if I understand your question correctly, but I would say that directionality 1 = 90 degrees beam (the light shoots straight from the light object's normals - like laser).

Hi Maru,
Let me re-phrase my question.
How should I adjust the Directionality parameter to match the Beam Angle of 60 degrees from the light's technical specification? Will it be (1-60/90)?
Thanks!

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: burnin on 2021-03-27, 12:06:17

a bit clearer animation of
directionality VS angle
what you assume, doesn't coincide

(https://forum.corona-renderer.com/index.php?action=dlattach;topic=32800.0;attach=145076;image)

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: romullus on 2021-03-27, 14:59:33

@burnin, your angle is incorrect, it shows 90°, when actual angle is 180° It's also quite strange why in your example light beam never goes completely parallel at 0° Maybe it's because of your scene's setup?

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: burnin on 2021-03-27, 18:15:07

Right, values are script-driven, so symmetry modifier makes total angle half size and I forgot to compensate. // tnx on notice :)

About 'strange' behavior @ 0° angle. It's natural. IIRC, there's no laser in Corona.
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=32800.0;attach=145092;image)
Maybe a bug? How's on Max?


 

To answer OP: "No, dependence isn't linear."
Also, gamma & quadratic function can be observed...

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: romullus on 2021-03-27, 19:43:36

Quote from: burnin on 2021-03-27, 18:15:07

Maybe a bug? How's on Max?

Looks about the same in Max. Probably it's expected behaviour. As you noticed, Corona light is not a laser even at directionality being at full strength.

Quote from: burnin on 2021-03-27, 18:15:07

To answer OP: "No, dependence isn't linear."

I wonder what's the reason behind this? I always thought that it is linear. Maybe it would make more sense to have directionality expressed in angle, instead of 0-1 range? @Team?

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: dsolod on 2021-03-30, 11:08:33

I would love to understand more about the Directionality parameter.

If it's not linear is it possible to correlate it with the light beam angle of the real lights?

I attached the scene with 3 IES lights taken from the Philips lighting website:
https://www.usa.lighting.philips.com/support/support/literature/photometric-data#led

My question is How to adjust the Corona lights to mimic the similar beam angles? Only by trials?
Any help will be appreciated

Title: Re: Spot light beam angle and CoronaLight Directionality
Post by: dj_buckley on 2021-03-30, 11:43:02

I raised this issue (or similar) a while back https://forum.corona-renderer.com/index.php?topic=23208.0