tree soft occlusion looks 2d

i am a beginner and dont have much exp with unity …i made this tree

in blender …was ok with it … i knew importing it to unity will cause it to look a bit different but it ended up looking flat as if it was a 2d image … i want those triangles to be visible…any help would be appreciated

i am not using textures …just plane materials…here is a pic of the material