On curved surfaces there are strange reflections. It looks like there is a problem with phong. On flat surfaces, it works fine. See attached render.
Sample file for Cinema 4D R18.028 with Corona A6RC2
https://www.dropbox.com/s/q9gptndh5j67wgm/phong.zip?dl=1
If that’s very low poly mesh, then this result is probably expected. I don’t have C4D, if you’d export those meshes to OBJ format, i could chech how it renders in 3ds Max.
Hello,
Smoothing groups maybe ? I don’t know how they name this in C4D, but at least in 3dsmax that’s something users regularly forget about 
Hey, try this :
N-side spline, R: 200cm sides : 200
duplicate it, Change the R for the thickness u want, if u want 1 cm R: 199 , 2cm R:198 etc
Edit splines, delete the part u want (see attachement 1), connect and delete the splines. Close the spline (join points)
Add a revolution with high subdivision for ur spline.
u will have a clean model.
Rémi
