Common mistakes when painting roughness 3D models usually involve over-saturating texture values, neglecting real-world material context, and inconsistent detail scale.
Over-saturating means using extreme roughness (too matte or shiny) that doesn’t match real materials—like a metal tool as soft as fabric. Neglecting context leads to mismatches, such as a glossy ceramic mug looking as rough as concrete. Inconsistent scale happens when small scratches don’t fit the model’s size, like tiny marks on a large outdoor statue that should have bigger weathering.
If you’re learning, use real material photos to guide roughness values and render test shots to tweak—this avoids unnatural results without extra tools.