What is that shadow?


I am a Blender beginner and I am trying to understand how glass works. By any means if I have a glass with IOR 1.00 it means, that glass has no refraction - simply put, light travels through it without any distortion. On top of that, if I set color to fully white, that glass should be perfectly invisible if not count for surface reflections. And here is my question… what is that shadow? I mean, how is a perfectly invisible object that is not causing any distortions to the light casting shadow? How do I fix this?

Google says, increase Light Paths, but as you can see I have already set them to 48.

Using the IOR value of 1.0 is saying it does not refract light, you are right…the IOR value of 1.00 is for Air… Did you change the setting for the Alpha Blend Mode?
It is at the bottom of the Material tab under Viewport settings…Blend Mode > Alpha or Hashed and change the setting for Shadow also…another thing is under Render Properties >Film> Transparent > Transparent Glass
For Glass, the true IOR value should be around 1.4-1.5…
I set this one up with an IOR value of 1.45…Alpha Blend… Screen Space Refraction and Translucency…
It will still cast a shadow, clear glass will always cast some shadow…


Thank you for pointers. I have not looked at blending mode, will have to experiment with it a bit. I still think that if we have object with IOR of 1.0 (Air) there should be no shadow or very slight one (because of surface reflections). We get shadow on glass because light gets refracted on “edges” as required by IOR. If material has no refractions (IOR 1.0) and allows light to pass directly there should be no shadow then because whole light ray should pass freely.

I will experiment a bit, but I think in the end I will accept that “it just work that way”.

Maybe this will shed some light on it. Don’t miss the link for “more details here”.

If you follow that link it appears that there is a lack of caustics leading to the shadow.

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That actually helps. Thank you :slight_smile:

Great, Your Welcome.