Two sided foliage issue

Hello, I have some problems with two sided foliage material.

Here is a bush you can find in starter content (SM_Bush) with a simple 2 sided material, in my scene:


everything works perfectly.

here is a bush i made, with the same setup but different color and normal


everything seems ok, but when i turn around (with the sun behind my character) this is what i get


this is really odd.
It’s like the meshes wich are 60/90° turned to the sun are not taking light properly, so there are planes with subsurface and planes without it.
This is really strange and I can’t find the solution. The cast shadow flag will not solve the problem. The material setup is the same, how can I solve this? Am I missing something?

I get the same problem with this wheat
this is a screenshot with the character in front of the sun


this is a screenshot with the sun behind the character


this is a mess, light is not affecting everything in a uniform way.
Any workaround for achieving a uniform look?

Thank you very much

It’s due to the geometry. The bush has way more detailed geometry than your meshes (probably) which allows it to more accurately be lit up by the lighting. See here, particularly the vertex normals bit Foliage - polycount

I don’t think it’s about polycount, I think it’s something related to vertex normal but I don’t know how to manage them :confused:

I tried to high the poly count and you were right.
More polys better light.

Higher polycount means more tris, which in turn means more verts and therefore more vertex normals. Adding more polys (especially via a smoothing subdivision method like turbosmooth/subD) can result in vert normals that better fit the ‘ground truth’ (the actual curvature you’re trying to represent) but not necessarily. For instance subdividing in Zbrush without smooth or using something like Tessellate (tension=0) in 3dsmax will give you more polys but the normals share the same direction as the edge loops/verts that they divide. Check out the polycount wiki jonimake shared. It means you can get much better lighting on your foliage with very low poly counts. Noor’s version of NormalThief (if you’re using 3dsmax) is great for this.

holy necro, why are you raising the dead!?!
anyway, here’s a nice vid for any noobies that haven’t learned this yet