How to use the lighting passes

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How to use the lighting passes

Postby stratified » Tue Jan 13, 2015 10:00 pm

stratified Tue Jan 13, 2015 10:00 pm
Hi everybody!

In this write-up I'll quickly explain how to set-up and use the new light passes introduced in OctaneRender 2.21. A light pass isolates the contribution of a light source. Each light pass behaves as if all the other lights in the scene are switched off. The individual light passes can be added togheter in post to recreate the original render or to tweak the individual contributions of each light. The light passes available in Octane are:

  • Sunlight: Captures the light contribution of the sun. Only useful when a daylight environment is configured.
  • Ambient light: Captures ambient light either from the sky in a daylight environment or from the texture in a texure environment.
  • Light pass 1-8: Light passes 1 to 8 capture the contribution from mesh emitters. Emitters (both texture and blackbody) have a light pass ID pin assigning an emitter to a light pass. It's possible to assign multiple emitters to the same light pass. If nothing is configured, all emitters contribute to light pass 1.

I created a small example scene (granted, not really a realistic scene). It consists of 3 sphere on a ground plane. The lighting of the scene consists of 3 planes emitting red, green and blue light and a daylight environment:
example_Beauty.png
Our example scene (daylight + 3 mesh lights).

nodegraph_setup.png
The nodegraph setup of the scene.


First we need to assing each emitter an ID to map it the desired light pass. We assign the emitters to light passes 1, 2 and 3.
emission_node.png
The light pass IDs are configured in the emission node.


Next we need to make sure we actually have the correct lighting passes enabled. We can do this in the render passes node:
render_passes_node.png
The light passes are enabled via the render passes node.


Each individual render pass will looks like this:
example_Light pass 1.png
Contribution of the red emitter.

example_Light pass 2.png
Contribution of the green emitter.

example_Light pass 3.png
Contribution of the blue emitter.

example_Sunlight.png
Contribution of the sunlight.

example_Ambient light.png
Contribution of the ambient light.


The individual passes need to be combined in post with the additive blend mode. Find attached the Octane project and GIMP and Photoshop project files demonstrating how to put it all back together again.

Please feel free to ask any questions if something isn't clear.

cheers, Thomas
Attachments
gimp_and_photoshop.zip
GIMP and Photoshop project files
(6.8 MiB) Downloaded 600 times
light-layers-tutorial.orbx
(116.97 KiB) Downloaded 544 times
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Re: How to use the lighting passes

Postby stratified » Thu Feb 05, 2015 3:07 am

stratified Thu Feb 05, 2015 3:07 am
Bumped this one up.
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Re: How to use the lighting passes

Postby ten » Thu Feb 05, 2015 3:49 am

ten Thu Feb 05, 2015 3:49 am
nice, thanks for this strat!

ten
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Re: How to use the lighting passes

Postby bepeg4d » Thu Feb 05, 2015 9:55 am

bepeg4d Thu Feb 05, 2015 9:55 am
:o big thanks Thomas :D
NZ team rocks :D BRAVISSIMI :D
ciao beppe
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Re: How to use the lighting passes

Postby glimpse » Thu Feb 05, 2015 10:20 am

glimpse Thu Feb 05, 2015 10:20 am
Great! =) thanks for taking time to explain things out.
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Re: How to use the lighting passes

Postby whersmy » Thu Feb 05, 2015 11:26 am

whersmy Thu Feb 05, 2015 11:26 am
Is this something like multilight? :o

I`m not sure when to use this option or what it contributes?
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Re: How to use the lighting passes

Postby prodviz » Thu Feb 05, 2015 1:24 pm

prodviz Thu Feb 05, 2015 1:24 pm
whersmy wrote:Is this something like multilight? :o

I`m not sure when to use this option or what it contributes?


Looks just like Multilight (nice). Each light having it's own pass.
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Re: How to use the lighting passes

Postby linvanchene » Thu Feb 05, 2015 3:10 pm

linvanchene Thu Feb 05, 2015 3:10 pm
Thank you very much for the detailed description and especially the tutorial files. :D

It helped me a lot to be able to quickly see and test in photoshop how each pass in "Linear Doge (Add)" mode contributes to the final result.
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Re: How to use the lighting passes

Postby stratified » Thu Feb 05, 2015 6:02 pm

stratified Thu Feb 05, 2015 6:02 pm
whersmy wrote:Is this something like multilight? :o

I`m not sure when to use this option or what it contributes?
prodviz wrote:
whersmy wrote:Is this something like multilight? :o

I`m not sure when to use this option or what it contributes?


Looks just like Multilight (nice). Each light having it's own pass.


Hi,

Yes, in Maxwell for example this is called multilight. In Vray it's used via VRayLightSelect.

The typical use case is in a studio light setup (e.g. car model render, product render, ...). It allows you to tweak lighting to some extend in post. But I guess the prodviz guys here on the forum can tell you more about that.

Another use case I see is using it to denoise renders. Some lights (small point lights or the sun for example) will have a higher noise contribution. You could isolate those lights in a seperate layer and denoise that layer and comp it back togheter afterwards. In theory that should work. Never tried it so I don't know about practice :mrgreen:

cheers,
Thomas
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Re: How to use the lighting passes

Postby prodviz » Thu Feb 05, 2015 6:24 pm

prodviz Thu Feb 05, 2015 6:24 pm
Nice idea.
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