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When using 2 point lights with lerp, it produces clipped artifact. Please help me clarify what's happening here and how to fix it. It bugged my mind for 2 days straight.

Hello, thank you for getting in touch and for your support!

The issue seems to be on the interpolator / Alpha value for the Lerp node, which is expected to be ranged between 0 and 1, so you'll need to add a Saturate node right before the Alpha input port.

Please let me know if this helps, thanks!

Got the same result with saturate. I think it has to do with something about how unity internally render each point light into texture first but I don't have detailed information about that topic. It's weird enough with how you have to multiply world space light pos which outputs 1 in this case, to get the correct color from lerp(it should do nothing because Amultiply by 1 should equal A).
here is gif of shader behavior.
At first I think it's because i multiply last node with world space light pos, anything that is not in light range will be output black. so I tried plugging out light pos
and got this.
As you can see, the band is still there. the band is also also screen dependent too.

I lose.

You might have to further adjust your nodes depending on the effect you're going for, after some testing it seems that adding the Light Attenuation data to the final multiplication rather than within the interpolation setup fixes this behaviour.

That...actually solved the problem. Thank you for your help!!

No problem, glad I was able to help!

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