# Normal map curved edges with black shading

I have been learning how to bake normal maps in Cycles for a little while. But I have run into a slight problem. I get these black edges/shading on curved edges.

So my question is. How can I fix/prevent this from happening? Also I am using a cage.

Reagrds, Koreenium

• Welcome to BSE, including more details in your question and uploading the .blend file will help you get more accurate answers, we can't see the shape of the cage or the high res object here, nor the baking parameters, you can upload the .blend file here: blend-exchange.giantcowfilms.com Jun 6 '16 at 9:17
• This is caused by the fact that the normal color (let's say R: 128, G: 192, B: 255 -> aka a normal pointing up when you view the normal map at about 45°) which defines the particular little space on the actual polygon which is also pointing upwards, let's say at a 88° angle compared to the camera view vector. The resulting angle of the vector pointing up for that little tiny space on the polygon is then 88°+45° which is far more than 90° and thus looks black since the ray as far as Cycles is concerned basically goes into the polygon. Jan 9 '17 at 17:01
• One way to "fix" this is by using fresnel to gradually reduce normal map strength at grazing angles. This won't help you in Game Engines I suppose but as far as I've seen they handle this little problem well as I only encounter it in rendering engines. Jan 9 '17 at 18:11

This is caused by the fact that the normal color (let's say R: 127, G: 192, B: 255 -> aka a normal pointing up at about 45° when you view the bitmap normal map in image editor) which defines the particular little space on the actual polygon which is also pointing upwards, let's say at a 88° angle compared to the camera view vector. The resulting angle of the vector pointing up for that little tiny space on the polygon is then 88° based on geometry +45° based on normal map which is far more than 90° and thus looks black since the ray as far as Cycles is concerned basically goes into the polygon.

Normal Map used in the above picture:

One way to "fix" this is by using fresnel to gradually reduce normal map strength at grazing angles. This won't help you in Game Engines I suppose but as far as I've seen they handle this little problem well as I only encounter it in rendering engines.

In my experience, lines around a mesh can often be caused by jagged edges and Smooth shading. See my answer here.