realism of the 2-sided material for leaves

[Rob Burns]

For the last few days I've been working on developing more realistic leaf materials for trees using the vray 2-sided material and have found some pros and cons to using it. Up close, when viewed from beneath or when the leaves are backlit, the 2-sided material definitely looks more realistic than a standard vray material in the way shadows show through on the back of the leaf. The problem is that when viewing trees as a whole, or a forested area, trees with 2-sided materials look muted and lack contrast between the bright and dark areas. I find this is most true when the trees are lit from the side or when you are looking down onto the tops of trees. I don't understand exactly how the 2-sided material works, but it seems like it renders both the front and back of the leaf then blends them based on the translucency setting. This would explain the lack of contrast since the sunlit side is being blended with the shadowed side and vice versa. Because of that I still find the best looking material for a forrest of trees is a standard vray material, with some glossy refraction and sss. I was wondering how realistic is the 2-sided material, and is there another way to see shadows through the leaves without losing as much contrast, like using SSS setup in a certain way.

[vlado]

The 2-sided material is quite realistic; however most people usually get the translucency values wrong. If you take a look at a real-world leaf you will see that the translucency value is quite high (i.e. if you look at a sunlit leaf from behind it looks a lot brighter than if you look at it from the front) whereas most people would typically aim for mid-grey which is quite a bit off.

Best regards,
Vlado