ThinWall (Diffuse) Transmission type - strange behavior

[SSmolak]

I think that ThinWall ( Diffuse ) Transmission type works wrong. If this was made for vegetation, leaves type of materials it should "transmiss" light only from direct sunlight - not from ambient ( or very little subtle from ambient ). Please go outside on evening and see how tree leaves looks

This is how it works without sunlight :

And this is how it should looks ( standard thin wall transmission ) :

This should works more like ThinWall but without transparency effect - transmit light only when camera is oriented directly to polygons that have sky behind.

ThinWall.zip

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I noticed that this works fine without sunlight using very small Transmission values. But after that if we want the same material to looks good ( with very good visible grass, leaves transmission effect ) using strong sunlight there is need to crank up Sun value to 1.5 or 2.

[bepeg4d]

Hi,
can you share the scene, instead of sharing only the movie?

ciao,
Beppe

[SSmolak]

Attached. Please see how strong Transmission react to ambient light. Please switch to Thin Wall ( no diffuse ) to see more natural behavior.

To compensate it there is need to add the same amount of Diffuse but after that Transmission effect is not as strong while using strong direct SunLight.

[SSmolak]

I was partially wrong. I did test tonight and there is leaves transmission from very low ambient behind them. But anyway I think that there should be independent IOR value for ThinWall ( diffuse ) to set how much strong light is needed to drive it.