Im really new to Unity so i need your help.
I have a problem, i have just built a level for my game in Cinema 4d, but when i import the meshes from Cinema 4d some are only visible from one side.
I tried to solve the problem by changing the normals of all polygons so that the normal faced outwards, this helped for some of the meshes, but there are still some that are invisible.
Please help me.
I’d think this may be due to inconsistent vertex winding, I’ve a model somewhere with the same problem where flipping the normals outward facing doesn’t help, nor does the ‘normal’ script on the wiki. I didn’t use the mesh in the end but knew this is probably why.
edit : Not that it helps, but I thought I’d try and fix said mesh to work out how to do it for you and I’m failing badly 
If I work out how I’ll edit this again. I’ve got Cinema4D but stopped using it as I fell for Blender at work and used it ever since. I’ll import it into C4D and have a play too.
Shaders usually have Culling On, which means backfaces won’t be rendered. Try using a shader that has Cull Off, and see if that fixes your problem. The vegetation 2 pass unlit built in shader has no culling, but I would only suggest using that as a test. If your mesh suddenly appears using that shader it means you need to fix polygon normals, but if they don’t show up at all, it means there is a problem with your export of the meshes.