How to Fix Mesh Edge z-Fight

Hi everyone~
I create a custom mesh to show the direction(forward backward right left up down), I want to enable edge to display edge, but it seems have z-fight, I can’t find any api to move edge a little with normal direction. Does anyone have any idea to fix it?
Thanks for any help :grin:
This is PG :
This mesh is prepared to replace box in :grin:

Sorry for its Chinese Notes , this pg is prepared for a series of Chinese Language tutorials. Please ignore them. zOffset and zOffsetUnits should do