UV Preservation

Existing UVs can be preserved by DCC Importer, as long as the material ingredients do not require texture baking. If baking is needed, then existing UVs are checked for overlaps and whether all UVs are contained within the 0-1 UV space. This is commonly called an "atlas" UV layout. If UVs do not fit these criteria, and the material ingredients require baking, then new UVs will be generated to prevent baking errors.

DCC Importer will always attempt to preserve the existing UVs if possible. It examines each material in depth, and chooses different conversion strategies depending on material complexity. 

Whenever a material uses geometry-dependent inputs, then these require baking. The shape of the model will have a direct influence on the material, and thus a tiling texture cannot be preserved as-is, but has to be transformed into an atlas layout. 

Geometry-dependent examples include: VRayDirt, VRayCurvature, Vertex Color, and procedural textures (e.g. Noise, Smoke, Checker, etc.). Additionally, features which rely on specific UV layouts such as UDIMs and Real-World Scale (RWS) will require texture baking as well.

The metal material on the left has no texture inputs, so the UVs are simply removed on output. The brick and fabric materials in the middle use textures and color adjustments, so they can re-use their existing UV layouts. The chipped-plastic example on the right uses procedural textures and edge wear, which are both geometry-dependent, so this material must be baked. If the existing UVs do not conform to atlas contraints, new UVs will be generated.