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[Blender] Can't figure out how to make light passes work

Posted: Fri Sep 11, 2020 10:55 am
by xandrm1
I assign IDs to my lamps, in Render Settings I click on the pass numbers to enable them. So here's the weird thing: clicking on [1] makes all my lamps appear. Clicking on [2] makes none of them appear, despite some of them having an ID of '2'. If I don't enable light IDs action, clicking on [1] disables all lights in the scene. I'm beyond confused.
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Lamp settings:
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In Object Properties tab of the lamp I found this. No idea what it does and how it works.
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As for the final light passes in a render, they come out exactly the same as in viewport. Any tips?

Re: [Blender] Can't figure out how to make light passes work

Posted: Mon Sep 14, 2020 12:46 pm
by funk
I use the modo plugin and only dabble with the blender plugin but I'll try to help.

- You don't need to change any of the render > kernel > light options. These are global toggles (eg to turn off all lights in light pass id 1 etc).
- You don't need to adjust object properties > light pass mask either. This allows you to exclude the particular object from being lit by a light pass id.
- It looks like your light node setup is incorrect too (its set up as a toon light), because you clicked "use nodes" while it was a point light.

The steps to get this working are:

1. Its best to add an area light (or change the point to an area), THEN click "use nodes" so the right nodes are automatically created for you (diffuse material + texture emission).
2. Then each light > texture emission > light pass ID should be set.
3. Enable the light passes under: View layer > passes > lighting
4. If you want to see each light pass in the preview, you can use: View layer > passes > preview pass. Make sure to set back to combined to see the beauty render later.
5. f12 to render. Each light pass will get its own slot in the pass dropdown list

I have attached a sample scene

Re: [Blender] Can't figure out how to make light passes work

Posted: Mon Sep 14, 2020 6:12 pm
by xandrm1
Hey funk thanks for such a detailed reply.

I actually got it working 2 hours after submitting this post, but couldn't take it back as it was already out pending approval from the forum moderators and was out of my hands.

It was exactly as you wrote to the letter. It was all because of toon lights which I generated exactly by clicking 'use nodes' on a point lamp. When I clicked 'use nodes' on an area lamp it generated proper texture emission->diffuse material and worked right off the bat. The "Light pass ID" in toon lights really got me fooled!

Re: [Blender] Can't figure out how to make light passes work

Posted: Tue Sep 15, 2020 6:25 am
by funk
I'm glad you got it sorted out :)