Blurry Shadows and Frosty Glass

[peerman]

So I can't find this anywhere, so I'll ask here.

I can't seem to create a material (frosted glass) that blurs the shadows after the light has passed through it.
The blurred glass should also blur the shadows behind it (I tried it with a real piece of frosted glass here at the office).
The only solution right now is to not let light through the glass and use an arealight.
I also tried a 2sided material but that doesn't have the appearance of frosted glass (the blurred refraction).

Is there some kind of setting I missed?

Any help appreciated!

Regards,

[Morbid Angel]

that's because you are probably using affect shadow option in refraction which is a fake method (cheap caustic) if you will. Unfortunately there is simple solution here. You can either fake it by making the shadow more blurry with area light (area shadow in dir light) or you have to use real caustics.

[andybot_cg]

yeah, you'd need caustics to get real-world soft shadows. I played with that a long time ago, but I found it hard to get the right caustics settings - when it looked smooth enough, then the edges became poorly defined; or else it was sharper edges, but the look was too grainy. If you can fake it, that's much simpler.

[peerman]

So I found a sort of solution. I checked the GI reflective box (under GI options). And got this result. I needed to set the Hsubdivs under irradiance higher for a smoother result. All in all quite nice already. Needs some tweaking so suggestions are welcome!
So this is without caustics on.
Thanks for all reactions!

[andybot_cg]

awesome! That looks to be very useful, thanks for the tip.

[ValeroStudio]

Looks cool to me!

[peerman]

First test on real scene (OK, early WIP of a part of Blijdorp Zoo Rotterdam).
Renders took about 15min, 1000x600px. Vray Sun only

[andybot_cg]

can you share that test scene (post #4)? I'm running a test on a scene similar to yours from a few years back, and I already have the GI refractive checked, but it's not giving me the soft shadows. I wonder if there's some setting in the material that needs to be checked as well.
Thanks!

[peerman]

Hi Andy,

Sure, here's the file: blurredshadows.zip It's in Sketchup 2015 format. If that's a problem let me know!
Also be sure to check the reflection GI... I think I meant that one earlier...
Good luck!

[andybot_cg]

Ah ha! There is a material setting that needs to be adjusted as well. "Affect Shadows" needs to be unchecked in the vrayBRDF material. The material I was using was the the old asgvis layered material instead of the new BRDF one. Affect Shadows disabled removes all GI through the material.

[andybot_cg]

no idea what you've done to make that material. I am trying to duplicate the material, and I've not gotten anything to behave the same way...

one thing: reflection glossiness! If your reflections are glossy @ 1.0 - then this trick does not work. Figure that one out!!

still trying to duplicate the material tho. Can you figure out what is different between the two materials?

[peerman]

So I found one difference that made the glass more transparent. In the defaultmaterial1 material your diffuse color is grey instead of pure black. When I changed the color both glass panels are the same.

[andybot_cg]

thanks - that does it. I was only looking at the checkboxes and numbers. Looks like black removes the diffuse layer completely, guess that's what we're after. Cheers!

[keduards_]

Hello everyone, I see this is a 2014 forum but after following the recommendations I'm still facing the same original problem.
Is there any update on this or new way to do it on V-Ray 5?

Thanks alot!

[konstantin_chaos]

Hi keduards_,

The only option for producing shadows blurred by a refractive material remains Caustics.
In order to set this up properly you have to disable the Affect Shadows option of the refractive material first.
You can then enable both the Refractive and Reflective GI caustics options in the advanced GI settings and see if the result is sufficient.
If not, you'll have to use the Photon Mapped Caustics (the rollout is called just Caustics in the latest Update).
If you share an image showing your exact setup I might be able to give you some more specific recommendations.

Konstantin