Turning off 'Force Vertex Shading.mobile' resulted in severe frame drops
I'm working on a mobile game. The world is 3D and the characters are 3D animated sprites (which are 2D really). I have an OmniLight node that shines on one of the character sprites. When 'Force Vertex Shading.mobile' (project setting parameter) is turned on the game runs smoothly, however, the character sprite doesn't cast any shadows. When I turned 'Force Vertex Shading.mobile' off, the character sprite started casting shadows but the performance dropped significantly.
How can I fix this? The shadows can be low quality (I have no problem with that) but I need them to be there.