Cosmetics 3D models are often grainy due to low-resolution textures, insufficient polygon counts, or compression during export.
Low-res textures lack detail for surfaces like product labels or bottle finishes, while fewer polygons make curved edges (e.g., lipstick tubes) look jagged; compression reduces file size but loses fine details.
To fix graininess, use higher-resolution textures (1024x1024 pixels or more) or slightly increase the polygon count before exporting—this smooths issues without adding excessive file size.