I guess it’s a bit late to answer this thread but just in case if someone will be searching for this,
I’ve been searching for this same problem just recently and seems like there is still no option to turn off self shadowing in UE4.26 but there are some workarounds, you can try plugging in your Color Texture with a Multiplier into Emissive and Subsurface Color which will allow you to sort of control the shadow’s intensity, don’t forget to change your shading model to Subsurface!
(Many thanks to this post!
Can a material cast shadows but not receive them - Rendering - Unreal Engine Forums)
Additionally you can try adding a really small value like 0.05 into your Opacity channel
(Many thanks to this one as well!
Unreal Engine 4 Stylized Rendering Workflow)
Oh and don’t mind the PixelDepth Lerping into Opacity Mask, it’s a separate optimization technique which cuts off the alpha on great distances, here is where I’ve found it
https://www.patreon.com/posts/25192376
(Triple thanks to all the authors!)
Also, bear in mind that those tricks can drastically lighten up your trees and make them much brighter!
RayTraced version is a bit darker in this case and actually looks pretty nice even without those Emissive, Subsurface and Opacity tricks from the start!
But those are just my small experiments, RayTracing is a different story for such stylized leaves, still trying out stuff myself, just hope this helps anybody!
