A normal map appears to be using input image with incorrect gamma. This can cause shading artifacts.



This message is displayed when Corona Renderer detects a CoronaNormal map containing a texture loaded with incorrect gamma.  



Normal Map - correct result:




Normal Map - incorrect result due to wrong gamma correction:




Solutions:

  • This can be easily automated for all materials in the scene using the Converter Script
  • Alternatively, you can perform a quick fix by enabling “Add gamma to input” checkbox in CoronaNormal map containing offending input
  • When loading bitmap file through the “Select Bitmap Image File” window, at the bottom part of the window, in Gamma section, click "override", and set its value to 1.0


Note: Corona Renderer will attempt to detect whether a normal map texture is loaded correctly or not, but it might sometimes fail. This will result in displaying this error message even if the normal map is loaded correctly, and the material is looking as expected. To learn more, see this short guide: How to use normal maps?