3D Shape: Classify 3D Shapes and Objects . 3D shapes can be classified into three groups – those that have only flat faces, those that have only curved surfaces and those that have a combination. 3D shapes with only flat faces are called polyhedral which is Greek for ‘many faces.’ . Once students can identify particular geometric features of 3D shapes and objects including surfaces, faces, edges and corners/vertices shapes can be described using these terms. Determining the difference between ge