On the new Toon Standard shader if culling is set to Front or Off, the backfaces are rendered darker than they should be compared to the commonly used PC shaders. This is caused by the backface normals facing the wrong direction. The solution for rendering backface normals as expected it so flip the normals. This is the default in Poiyomi, and an option in Liltoon.

Expected: Front and backfaces render with the same lighting.

Actual: Backfaces are rendering much darker.

Provided image shows four copies of the same avatar.

The small feathers face the viewer like normal.

The bottom right avatar is the traditional version, where the large feathers were duplicated and flipped, so they face the viewer. This avatar renders as expected.

The remaining three copies have only one layer of the large feathers, all facing away from the viewer.

Top left is the backfaces being rendered with flipped normals.

Top right is a demonstration that when the backfaces are not flipped the results match the current output of Toon Standard.

Bottom left is Toon Standard, which is not flipping backface normals.

SDK Version: 3.8.1