could you create an invisible projecile that relays and when it hits any brick it turns visible?
no. a couple things are wrong with that idea: one being you cant just toggle on or off the visibility of a projectile
the only real way to do this is to spam raycasts from the handle upwards relative to the way the player is looking, but this is likely a very spammy and bad idea and wouldnt really result in a good looking effect
the saber would clip through the wall anyways so its not like its going to look good when its touching a wall.