I'm trying to light a bottle with several light emitting planes. In front of those planes I have planes with SSS to get diffused light. I switched off shadow and camera for those objects, but still they cast a shadow of themselves. Any pointers how to get rid of them?

I circled where those planes are located and the cast shadow. enter image description here

  • $\begingroup$ It's hard to tell without a scene, but my guess is that these aren't shadows. Planes and area lights emit to the front (planes in the back too), but not to the sides. Assuming the emitters are perpendicular to the ground, then any point exactly underneath the plane will not receive any light at all. $\endgroup$ – Stefan Werner Jan 29 '17 at 16:38
  • $\begingroup$ OK. So I'd have to curve the plane at the bottom to prevent this from happening? And the have some sort of falloff to prevent too much extra light on the ground... Or so. Or is there a more intelligent solution? I need strip lights, high, but narrow, so I can only use area lights/planes , as far as I know. I'll try to lift them off the ground a bit to get some more of the environment light in there. $\endgroup$ – Markus Schlögl Jan 29 '17 at 17:35
  • $\begingroup$ You could also render the scene once with and once without that light and composite the two renders, if all you need is a single shot. $\endgroup$ – Stefan Werner Jan 29 '17 at 18:05
  • $\begingroup$ I'm afraid these specific lights influence the surrounding too much - if I take them off and comp 2 images, they'll be too different from one another. Unless there's nome Blend-Fu I'm not aware of (90% probability)! $\endgroup$ – Markus Schlögl Jan 29 '17 at 18:23

This is less about casting a shadow and more about how the plane is emitting directionally. Specifically, there is no emission coming from the infinitely thing plane along the bottom. That missing illumination is what is causing the missing result.

A mesh lamp with a degree of thickness should alleviate that phenomena. Otherwise one would need to craft additional illumination or a gobo to hide the peculiar result.

  • $\begingroup$ Additional illumation it'll have to be - I extruded the mesh, and now I have no more shadows, but light spots. $\endgroup$ – Markus Schlögl Jan 29 '17 at 18:05
  • $\begingroup$ It actually ist the SSS plane that causes this - the light in front of it is always a lot brighter than behind it... $\endgroup$ – Markus Schlögl Jan 29 '17 at 18:36

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