Common mistakes when applying roughness in 3D models include mismatching values to material types, inconsistent texture alignment, and ignoring lighting interactions.
Mismatching means using the same roughness for different materials (e.g., glossy metal vs. matte paper), breaking realism. Inconsistent alignment happens when roughness textures don’t match base color/normal maps (like a brick wall with smooth roughness but textured color), causing visual clashes. Ignoring lighting means not adjusting roughness for the scene—too rough in bright light makes materials look flat, too smooth in dim light looks overly shiny.
For better results, use real-world references (e.g., photos of matte notebooks or shiny toys) and test values in your scene’s lighting to avoid guesswork.