Dark edges on liquid

[Kim Laughton]

I'm sure this is a super simple question - but not sure how to fix. I'm wondering where the dark edges on this liquid are coming from?

[kagemaru]

I'm sure this is a super simple question - but not sure how to fix. I'm wondering where the dark edges on this liquid are coming from?

[ATTACH=CONFIG]35439[/ATTACH]

Not really simple.
I think it's the "meniscus effect". You can read about it here where even Pixar had to deal with it. I guess a combination of ray depth, exit color, IOR, caustics and curvature and maybe other ways can solve the issue, but i'm just randomly guessing without a scene.

[Kim Laughton]

Not really simple.
I think it's the "meniscus effect". You can read about it here where even Pixar had to deal with it. I guess a combination of ray depth, exit color, IOR, caustics and curvature and maybe other ways can solve the issue, but i'm just randomly guessing without a scene.

Ah - interesting, thanks! I think maybe this is a different thing however - meniscus is the curve you get at the edges of a liquid which I guess doesn't happen on a beach because the sand is waterlogged or sucking up the water so Disney wanted to get rid of it - but had it from their water sim. In this case there's no meniscus because the liquid/gel isn't simulated, it's just a lump poking up from below. It's maybe something to do with shadows (checking 'Affect shadows' removes it but then makes things look wrong), maybe the distance between surfaces getting too small?

[Kim Laughton]

Here's the same thing happening with a cube and transparent material. Looks correct on the left but move it down close to the other surface and it goes dark.

[kagemaru]

[ATTACH=CONFIG]35460[/ATTACH]

Here's the same thing happening with a cube and transparent material. Looks correct on the left but move it down close to the other surface and it goes dark.

Looks shadows or "lacking GI" thanks to objects proximity to me. How about a cheap trick like no shadow casting from the liquid, or GI visibility, or a more expensive one like using caustics.

[Kim Laughton]

Looks shadows or "lacking GI" thanks to objects proximity to me. How about a cheap trick like no shadow casting from the liquid, or GI visibility, or a more expensive one like using caustics.

Hmm, changing the GI settings for that object (or even turning it off for the whole scene) doesn't make a difference to the dark edges so I guess not GI connected. Turning off shadow casting for the object solves the problem but then the liquid looks wrong - all as dark as the edges, the same as toggling affect shadows in the material property.

Never used caustics but if it's a shadow issue I wonder if that could solve it?

[Kim Laughton]

Ah! It's a dome light thing - turning off cast shadows from the dome light (with an HDRI) totally solves the problem and then the liquid behaves as expected. The other lights in the scene (a plane and a sphere) are fine with shadows left on. I guess it's a bug?

Edit - turning up the fog multiplier in the material and the problem comes back again even with the other lights. Urgh...

[Kim Laughton]

Sorry to resurrect the thread, but contacted support and they said it's solvable by reducing the shadow bias in the sampling settings on the light. Thought this might be useful to know if anyone searching digs this up.