To make a 2D image-derived 3D model smooth, use subdivision surface modeling (splits polygons into smaller, smoother shapes) or normal/bump mapping (fakes depth with texture data).
- **Subdivision**: Softens hard edges by dividing existing polygons, preserving the 2D design’s form—ideal for organic objects like characters. - **Normal/Bump Maps**: Avoid adding polygons; use texture pixels to make flat surfaces look curved (e.g., simulating smooth metal or skin on low-poly models).
For beginners, try Blender’s "Subdivision Surface" modifier (set "Viewport Levels" to 1-2) or bake a normal map from a high-poly version of your 2D shape—simple ways to add smoothness without complexity.