Flipped normals and inconsistent shading of speedtrees in UE4

Let’s go step by step.

  1. In SpeedTree, I create my plants, trees, etc. making sure all normals are consistent.
  2. Import .srt into UE4. Some of the faces have been flipped!
  3. This causes the plants to shade incorrectly. The backsides of these flipped faces look like they’re receiving direct light.
  4. Multiplication of the normal map with ‘two-sided sign’ node causes both sides of a face to receive same lighting information which makes it undesirable.

So is this issue happening during SpeedTree’s export or UE4’s import?
I’ve posted this issue even in the SpeedTree forums.

I sincerely request the UE4 developers to fix this problem so that we can have great looking foliage.

Screenshots with descriptions here.
http://postimg.org/image/6tym5fi2p/

Is it a problem you have only in the editor or also if you press play?

That’s important for speedtree.

The SpeedTree developers solved the issue. For two-sided geometry, on fronds, the frond : flip option should be set to none.
On leaves, the leaves : flip option should be unchecked.