Black Halo around edges

[jigu]

Hello,

I am doing "Splash" rendering using "Coronamaterial". I have "Absorption" and "Scattering" set to 180 white and enabled. I set refraction value to 1.0 with IOR of 1.0 and reflection is on with IOR 1.33.

And other geometry like ocean surface and whales/creatures are set to "Shadowcatchermaterial" with shadow opacity set to 0.1.

In exr renders I am getting black halo around edges in After Effects (in linear space)

Is there a way to workaround this?

Thanks,
Regards,
Jignesh

[maru]

Hi, it's hard to imagine all the things which you describe. Images would be great. :)

I suspect what you are referring to is black pixels sneaking into alpha channel. Try googling for "premultimplied"/"unpremultiplied" alpha.

[jigu]

Hi,

Sorry for not posting image an earlier.

Here is the image. Yes, it's set to "premultiplied" in after effects. And also set linear space in After Effects.

[maru]

I am still not sure what it is. What is the expected result?
It looks like the water has some shadows on it - does it have some diffuse color?
Or maybe the dark areas are refractions of the shadowcatcher object?

[jigu]

Edge should blend in with background. Here I set background grey color.

in the middle of splash, you can see whale matte object against splash. There isn't black edge happening over whale matte. But it (black edges) happens around splash geometry.

Here is the viewport screenshot.

[maru]

Why does the whale have shadowcatcher material? If you remove the whale (just for a test), are you still getting the dark outlines?

[jigu]

whale and ocean has shadowcatcher material too. I want to render "splash" as separate pass so I can comp in post. Splash particles are meshed in metashape using Frost.

[maru]

I am not sure about this setup.
Wouldn't it be better if the whales and ocean had rayswitch material with all slots used except for direct visibility? (they would affect reflections, refractions, gi, but be invisible directly)
I think the black areas are simple the shadowcatchers reflected/refracted in the water.

[jigu]

Oh then it seems shadowcatcher material. But with "rayswitch" will I get shadow on ocean surface? I will check that soon once my current render is done.

[jigu]

I tried "RayswitchMtl" and it doesn't work. I removed material from "Direct" visibility slot and it didn't make matte material on whale. I am looking to assign "matte" material to other objects other than splash. (like whale and ocean) and still able to get proper edge blending like we do get in other renderer and no black halo.

I am using corona 1.3.

[romullus]

Unfortunately Corona hasn't matte material yet. It is highly requested and hopefully will be there sometime before v2.0 (nothing official though).

[jigu]

Though applying "Shadow/Hightlight" effect in After Effects remove that black halo around edges. So that solved for me for now. Next time I will keep in mind. I thought "Shadowcatcher" is something mimick "matte" material in Corona. None the less, I love volumetric/SSS rendering of corona.

[jigu]

Any workaround to render other objects as matte object in corona? How would you do this?

[maru]

Can you post a reques about this in the support? Corona-renderer.com/help
I think it should be possible to do this, probably using some crazy rayswitch+shadowcatcher setup.

[jigu]

I think no material in Rayswitch GI slot and "shadowcatcher" in direct visibility slot does the trick. I tried and it seems worked but I haven't checked result in post how it looks.