Normal Mode Specifies the mode HDRP uses to calculate the normals for back facing geometry.
• Flip: The normal of the back face is 180° of the front facing normal. This also applies to the Material which means that it looks the same on both sides of the geometry.
• Mirror: The normal of the back face mirrors the front facing normal. This also applies to the Material which means that it inverts on the back face. This is useful when you want to keep the same shapes on both sides of the geometry, for example, for leaves.
• None: The normal of the back face is the same as the front face.
This property only appears if you enable Double-Sided.