Full invisible area light

Use this forum for general user support and related questions.
marcatore
Donor
Posts: 415
Joined: Wed Jan 10, 2018 8:04 am

Full invisible area light

Post by marcatore » Tue Jun 30, 2020 12:40 pm

HI,
I've read some messages on LuxCore Discord server to get the area lights invisible in terms of direct visibility and in terms of shadows.
Tipical situation is an area light near a ceiling.
I've tried to setup the light like suggested but it seems that some occlusion still existing and it reveals the area light shape.
I'm attaching a simple scene.
The scene contains 2 area lights. One visible and the other one invisible (the right one looking through the camera).
Is it possible to make the area light completely invisible? Just an "invisible" emitter?
I'd like to still use the MIS so opacity on a mesh light is not the best solution.

Thanks in advance
InvisibleAreaLight.zip
(92.08 KiB) Downloaded 9 times

User avatar
B.Y.O.B.
Developer
Posts: 3622
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: Full invisible area light

Post by B.Y.O.B. » Tue Jun 30, 2020 1:01 pm

To give a bit of context, what we have here is a meshlight which is invisible to the camera and has a white shadow color. Despite that, it still throws a slight shadow on the wall.

My response on discord was:
@marcatore It looks like the shadow color is not considered for global illumination rays.
When I change the ground plane to black matte, the shadow disappears. I think it comes from the fact that the whole wall is lit up slightly by indirect light from the ground, but this indirect light does not respect the shadow color and is blocked by the area light.

marcatore
Donor
Posts: 415
Joined: Wed Jan 10, 2018 8:04 am

Re: Full invisible area light

Post by marcatore » Thu Jul 02, 2020 6:57 am

Thank you for adding details.

let's see for the Dade's reply

User avatar
Dade
Developer
Posts: 4393
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Full invisible area light

Post by Dade » Thu Jul 02, 2020 11:19 am

I should have fixed this problem.
Support LuxCoreRender project with salts and bounties

marcatore
Donor
Posts: 415
Joined: Wed Jan 10, 2018 8:04 am

Re: Full invisible area light

Post by marcatore » Thu Jul 02, 2020 1:44 pm

Is it correct that the reflection of the "invisible" light is weaker than the visible one?

I'm doing some tests...it seems that also the direct light is weaker.
I'll post some images.
Last edited by marcatore on Thu Jul 02, 2020 2:06 pm, edited 1 time in total.

User avatar
B.Y.O.B.
Developer
Posts: 3622
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: Full invisible area light

Post by B.Y.O.B. » Thu Jul 02, 2020 2:06 pm

It looks like it is now partly invisible in glossy reflections and completely invisible in specular reflections.
From left to right: meshlight completely visible, meshlight invisible to camera and shadow color white, meshlight opacity = 0
At least it doesn't create noise like the meshlight with opacity = 0.
Attachments
floor is metal
floor is metal
floor is mirror
floor is mirror

marcatore
Donor
Posts: 415
Joined: Wed Jan 10, 2018 8:04 am

Re: Full invisible area light

Post by marcatore » Thu Jul 02, 2020 2:39 pm

I've test the invisible light with direct light. It seems that it emit less light.
I've attached a PSD with the 2 images that show the lighting difference.
invisibleLight_difference.zip
(2.68 MiB) Downloaded 5 times

User avatar
Dade
Developer
Posts: 4393
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Full invisible area light

Post by Dade » Fri Jul 03, 2020 1:25 pm

B.Y.O.B. wrote:
Thu Jul 02, 2020 2:06 pm
It looks like it is now partly invisible in glossy reflections and completely invisible in specular reflections.
From left to right: meshlight completely visible, meshlight invisible to camera and shadow color white, meshlight opacity = 0
At least it doesn't create noise like the meshlight with opacity = 0.
I have fixed that problem too. But note: the highlights, on the floor plane, aren't going to be exactly the same due to the indirect light received by the back plane, etc.

RGB_IMAGEPIPELINE_0.jpg
Support LuxCoreRender project with salts and bounties

marcatore
Donor
Posts: 415
Joined: Wed Jan 10, 2018 8:04 am

Re: Full invisible area light

Post by marcatore » Fri Jul 03, 2020 2:38 pm

Well..that it's more "correct" than before where the reflection was darker.
As soon as I can I'll test also the direct light. Or do you already test it? It's now the same?

User avatar
B.Y.O.B.
Developer
Posts: 3622
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: Full invisible area light

Post by B.Y.O.B. » Sat Jul 04, 2020 9:02 pm

Awesome!

Post Reply