In the RVT it seems like the normals are messed up. I’d need to see the material to say how, but most likely they are in the wrong space (world instead of tangent or something like that). Or you need to invert the normals on part of the grass using the two sided sign node.
In the first 2 pictures, this is the expected behavior. Forget about grass for a second, and imagine a wall. The side of the wall that faces the sun will be more brightly lit than the side that doesn’t. The side facing the sun may be brighter or darker than the terrain depending on how high the sun is in the sky.
The grass is like a ton of tiny walls, so naturally they have a dark side too. At least, by default. While this is technically accurate lighting for the geometry, it’s not really how we perceive surfaces like grass at a distance. So to better match the expectations of our perception (which is that the grass is lit in the same manner as the ground), grass is usually given the same normal vector as the underlying terrain.
One way to do this is to sample the RVT normals and use them instead. Which takes us to the third picture where I assume you’re doing just that? But if you do it wrong, it’ll mess the lighting up even worse.
Sorry I forgot I made this post, With the first 2 images is there a way to turn off this effect of the directional light shining bright on one side and dark on the other or at least be able to control how much the grass is effected? It looks horrible especially when turning and moving around.
This is UE 5.3 and it’s fine. ( Except the weird grainy shadows which can be fixed by setting global illumination to below high setting but cant be fixed in above versions. )
Show the normal buffers in each to compare. The grainy blotchiness is likely caused by the setting “affect distance field lighting” - disable this.
Also you should probably use the “two sided foliage” shading model, not the default lit model.
As you can see, your old project has completely different normal vectors, which is why it looks different. The normals are pointing straight up, most likely the mesh normals were modified because the material doesn’t have anything that would cause that.
As you can see, the ground is blue (facing up) and the grass in pic 1 is also blue (facing up).
In the second pic, the grass is not blue, meaning the normals are not facing up. Watch the video I linked again as it explains this.
That setting is in the foliage actor panel. Same place you change other settings for the grass.
The two sided foliage model allows light to transmit through the blade of grass, like it does with real leaves.
Okay I figured it out, UE 5.4 + has “Recompute Normals” set to true automatically on the import settings tab. Thank you for helping me I appreciate it! And with the other lighting problem it looks like it might have been a bug? Because now it’s no longer a problem, although there is also another weird thing happening now, maybe intended or a bug who knows anymore.
And for the grainy shadows it’s better now up close, it’s still visible but negligible, unless you get further and further away then it’s really noticeable. Which is fine I don’t expect everything to work as it should immediately.